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SOHC.co.uk Forums => Project Board => Topic started by: mattsz on October 25, 2018, 01:08:44 AM

Title: New (to me!) '77 CB400F - US model
Post by: mattsz on October 25, 2018, 01:08:44 AM
The new bike just arrived!  Since I've only really got storage questions at this point, I'll start here...

I stumbled upon this bike three years ago; it was sporting 21.7K miles on the odometer and a pretty orange and white for-sale sign, so I stopped and took a bunch of photos.  Interestingly, at that time I didn't take any pics of the whole bike, just detail shots.  I called the seller about it then; turns out he was a friend who invited me to take it for a ride. It needed some tuning, but it ran pretty well. It had some condition issues. I wasn't really looking to buy a bike, and I didn't - but he's come calling now to trick me into taking it off his hands.

Here's those photos:

https://photos.app.goo.gl/KAHnNEBDir375PbSA

And here's a little youtube video of it running - it was a warm start - it took a few kicks and some throttle juggling to get it to catch, but it idled well once it did.  I think I was focusing on noises, not knowing what's normal...

https://youtu.be/Szxke8bD_dg

Today...

It was last registered on August 3, 2016, and was put in storage at some point after that riding season.  The guy who was storing it for the owner just dropped it off and filled me in - he said drained the fuel tank, but not the carbs.  It was stored in a garage, uncovered, so it's very dusty.  He kicked it over occasionally, and it easily kicks through now.  The battery is stone dead, and the electrolyte levels are uniformly down about an inch.  It's topped up with oil, but I don't know how old it is.  The guy says it was "running great" when it was put away.  The air cleaner looks brand new.  Some of the obvious rust spots in the photos aren't as apparent at the moment, but I doubt they've been cleaned up or painted.

I'm new to Honda fours, so:

Can I assess the carbs without removing them?  I thought I might remove them for a winter once-over, but the "storer" says they'll be difficult to remove, and even harder to reinstall as the the rubber mounts will probably be hardened and expensive to replace.  He thinks I should just try to run it, but two years is a long time with fuel in...

I removed the tank and brought it indoors - the inside looks good and rust-free around the opening, but I can't see down to the lower recesses.  There is a certain stale petrochemical odor within.  I worry that there may be condition issues low-down where I can't see.  Should I just leave it for the winter?  Oil the interior somehow, perhaps?

When we took it off the trailer, I grabbed the front brake at one point to steady the bike, and the wheel locked up.  We backed it into my garage with the non-spinning front wheel leaving a rubber trail behind it.  A few more solid brake lever cycles allowed the wheel to free up some; the wheel turns, but the caliper is still sticking hard.  I can't imagine it's trustworthy without attention - worth removing for a winter overhaul?

I think that silencer crack didn't extend all the way around, and I don't think it leaked three years ago - but it looks like it encircles the whole thing now and I think it might have some black soot around it...

Might I salvage the battery, at least for testing purposes, by topping it up with distilled water and giving it a charge?

I don't have room in my unheated garage to store it; my next-door neighbor will keep this winter in his "basement"; I haven't found out whether it's heated or not, his whole bottom level seems to be a big garage.  But he says he has room along side three other bikes...

I found the original owners manual under the seat - I haven't seen any like it on the internet.  Maybe I'll duplicate it over the winter and make it available...

Any thoughts or input would be welcome...
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 25, 2018, 01:10:04 AM
By the way - the passenger foot pegs on the swinging arm are a hilarious feature!  Why on earth...?
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on October 25, 2018, 08:06:07 AM
It is unlikely you will save the battery but if you have a trickle charger(not a standard car one) you might as well try.
The front brake will deffinnately need overhaul. Undo the two bolts that hold the caliper together then put the big half in a bucket and use the master to pump the piston all the way out. Also remove the swinging bracket from the forks then come back for more advice.
Title: Re: New (to me!) '77 CB400F - US model
Post by: Nurse Julie on October 25, 2018, 08:44:33 AM
Strange spec bike as for a 1977 it is the correct colour, Candy Antares Red but the rear foot pegs position being on the swing arm makes it the earlier model. Great collection of photos.
Title: Re: New (to me!) '77 CB400F - US model
Post by: hairygit on October 25, 2018, 09:16:44 AM
Strange spec bike as for a 1977 it is the correct colour, Candy Antares Red but the rear foot pegs position being on the swing arm makes it the earlier model. Great collection of photos.
We had this discussion a while ago nursey, for some reason many of the U.S. F2's still had footrests on the swingarm.

Sent from my X6pro using Tapatalk

Title: Re: New (to me!) '77 CB400F - US model
Post by: Nurse Julie on October 25, 2018, 09:35:59 AM
Strange spec bike as for a 1977 it is the correct colour, Candy Antares Red but the rear foot pegs position being on the swing arm makes it the earlier model. Great collection of photos.
We had this discussion a while ago nursey, for some reason many of the U.S. F2's still had footrests on the swingarm.

Sent from my X6pro using Tapatalk
I missed that discussion Mr Hairy 😀😀😀 Good to know though.
Title: Re: New (to me!) '77 CB400F - US model
Post by: Sprocket on October 25, 2018, 11:31:13 AM
IMHO take the carbs off before running it, and clean them out individually. Rusty gunge will form inside and even if you can get the bike running you risk sucking the gunge into the engine and potentially damaging it or at least making it wear more. If the carb rubbers are hard, warm them up with a hairdrier for a few minutes before taking them off.
Interesting about the Antares red / early swingarm. Not seen that configuration before. Would be good to get some shots of the whole bike too, I can only see closeup shots.
Looks in very good condition though, lovely job :)
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 25, 2018, 11:31:58 AM
We had this discussion a while ago nursey, for some reason many of the U.S. F2's still had footrests on the swingarm.
I missed that discussion Mr Hairy 😀😀😀 Good to know though.

Actually, Nurse Julie, you did put in a brief appearance during one of the footrest discussions - but it was almost four years ago, and since I myself have trouble remembering if I put on my underwear this morning, I won't hold it against you if you don't recall the discussion.

I am curious to know, however, why the swingarm footrest setup was "fixed" in your market, but continued in ours...
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 25, 2018, 11:48:45 AM
Thanks for the battery and carb suggestions, guys!

I have a regular "automobile" charger/starter booster, and a low power (0.75A) battery "maintainer" - I'm told that the little one won't charge a dead battery, but as long as nothing will get damaged (charger or battery), I guess it can't hurt to plug it in after topping up the cells.

I can't think why I didn't take any "whole bike" photos back then, I guess I was only interested in detail shots showing condition.  I'll try to take a few today, but it's kind of stuffed into the corner at the moment.  Anyway, it looks a lot like all the other ones...  ;)

Is it difficult to remove the carb bowls in situ for a cursory investigation?  If I do remove and examine/clean the carbs, it definitely won't run until next spring.  I'd like to change the oil either way, I suppose I can try to warm up the sump before I drain it?  Any harm in connecting the big battery charger/starter booster instead of a battery to crank it over in an attempt to circulate some new oil?
Title: Re: New (to me!) '77 CB400F - US model
Post by: TrickyMicky on October 25, 2018, 01:24:09 PM
Hi Matt, Welcome to the "Grazed Knuckles" brigade. Regarding the carbs and tank, I left my bike standing for approx. 11 years, inside of tank was perfectly ok, fuel had 'gone off', just cleaned tap and replaced fuel line from tank to carbs. The carbs, now that's a different ball game! Removing them is a bit of a pain, but nowhere near as bad as trying to remove the float bowls whilst still installed. Because I had not drained the float bowls either, every jet had to be replaced, and I then refitted carbs only to find fuel running from overflow tubes when first turned on! I had omitted to remove and clean the brass spindles that the floats pivot upon, all gunged up and stopping the floats from operating. Whilst carbs are removed, have a dig through all the auction sites as I managed to obtain a nice set of socket headed screws to secure the float bowls with, meaning that if needed, the bowls can be removed more easily in situ using a small Allen key. Not too sure about your driver's footrest position, and it's definitely got the wrong gear lever, it should have two rose joints and a Johnson Rod for adjustment. Obviously the battery on mine was knackered, so every few weeks I just used to spin the motor over by using a set of 'jump' leads hooked up to my car battery, stops all the seals from going too hard. If you go on the "Flickr" website and just type in 400/4 there are loads of pics, which if you zoom in on them you can see what I mean re. gear linkage/footrest, might be worth checking on the rear brake pedal as well, it should have a guard fitted to it to stop your foot rubbing on the clutch cover.
    Regards the front brake, as they say in the trade:- "They all do that mate", remove caliper, new piston & seal, clean up the pivot pin and coat it with copperslip anti-seize on re-assembly. Have fun. Regards, Mick.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 25, 2018, 02:03:46 PM
Thanks Mick!

I see what you mean about the brake pedal, but re. the footrests and shift lever... I'm a bit on information overload at the moment, but didn't I read somewhere that the USA spec for these bikes included higher bars, and footrests mounted further forward for a more upright rider position?  Could it be that what I have is original to the USA bikes?
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 25, 2018, 02:11:26 PM
I wonder what's with the fuel tank filler cap cover?  Why do we need two?  It's ugly, and it has scuffed up the tank paint...

(https://lh3.googleusercontent.com/9LNdjPVL0hhQSqrV0rudo-fYHO8cSJ_APnqGABwoaGe4V0-6DULvKcaIHjbjLps36_FZEI5ISs1UNmAam3QSpU7CUahMoAVL0KW1KIR1JL20m_69LJiCHULAhZOgDWsJLIXZIkP1hgf4Al8DqXfzZ65ZhjJRq0efMLjUij8pOVkroINqp8tb6H-3E6Hg2GZVgA5jtsSjJ_BqSilhZWCzx8HbsEFWDHe5--ZPatpV7R_oPC2QBkRns996zqI_Wf56orNH0TGK-uNmNQinnt9GSN_TaQTubrDpxNl0diKRtPJcOjUnm28KGAhxo0aNTZLYC3P4tyn1rdbe1zz4I-A9JkciBx5VCBcJxUurbs9WMx7qUr74tJfC2UHN0yqnVDGJTiEdmakW2w2T6o_HW_hfxIoOrp4bnXMIeb2PwUZs883a-Ghc9Q7KNOeNLibKc1FVHh7JR5aUJBZMFdMReXWLomGPozcGltRo4lGqtjptbFU0hG8rF6bGFtP-p_br7XiIhiOkrVrEoauwqg7sAbbp7iDpISYBzv27D3T1RRyKoEEDGO5NXcq6E5ZcMXDDdy2PdYQdBtY9G8Ef4QYV0pu-PUIkDpc-czYNmRe9Wz5ZOiHs-C6wMDsYjbt915QZTFZwOzKYplx9rwLsBL8FG9CMDYhHR5QgT1hb0PrDygPrgoaQwYhJV6zeeqXsrejfT6L6pSUzVnrnxMDeksyfXQ=w1524-h1142-no)
Title: Re: New (to me!) '77 CB400F - US model
Post by: hairygit on October 25, 2018, 02:32:30 PM
The filler cover flap is due to your totally paranoid road safety people! It arrived on the 750's as well in 1975 on the 750F1 model, but they just made them like it for the whole world market, not just the U.S. then.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 25, 2018, 02:39:54 PM
The filler cover flap is due to your totally paranoid road safety people! It arrived on the 750's as well in 1975 on the 750F1 model, but they just made them like it for the whole world market, not just the U.S. then.

Not quite sure how it makes anything safer, though.  My '75 BMW, '00 Kawasaki and '11 Royal Enfield all had/have single covers... (https://advrider.com/f/styles/advrider_smilies/ne_nau.gif)
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 25, 2018, 02:47:01 PM
So what IS the story with this front brake?  Is it a sliding caliper type that only slides when you slide it yourself?  I've never seen an adjustment system like this...
Title: Re: New (to me!) '77 CB400F - US model
Post by: Nurse Julie on October 25, 2018, 02:52:38 PM
We had this discussion a while ago nursey, for some reason many of the U.S. F2's still had footrests on the swingarm.
I missed that discussion Mr Hairy 😀😀😀 Good to know though.

Actually, Nurse Julie, you did put in a brief appearance during one of the footrest discussions - but it was almost four years ago, and since I myself have trouble remembering if I put on my underwear this morning, I won't hold it against you if you don't recall the discussion.

I am curious to know, however, why the swingarm footrest setup was "fixed" in your market, but continued in ours...
Blimey, 4 years ago was a past life for me 😀😀😀
Title: Re: New (to me!) '77 CB400F - US model
Post by: Nurse Julie on October 25, 2018, 02:55:12 PM
So what IS the story with this front brake?  Is it a sliding caliper type that only slides when you slide it yourself?  I've never seen an adjustment system like this...
If you are on about the arm, It's a floating calliper set up. Needs to be set correctly to function correctly.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 25, 2018, 03:03:00 PM
Blimey, 4 years ago was a past life for me 😀😀😀

I know, right?  Let's see...... yep, I do have my pants on...
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 25, 2018, 03:10:42 PM
So what IS the story with this front brake?  Is it a sliding caliper type that only slides when you slide it yourself?  I've never seen an adjustment system like this...
If you are on about the arm, It's a floating calliper set up. Needs to be set correctly to function correctly.

I'm sure that's true, but I'm trying to understand how it works and why it's designed the way it is.  IIRC, my Kawasaki's Tokico caliper doesn't have any adjustment screws, it simply slides on pins as needed to equalize the piston forces...

I opened up the master cylinder reservoir, found the fluid low and very dark-looking (no surprise), replaced the cap and gave the lever another squeeze - front wheel is now solidly locked again.  Might I free it up by loosening the adjustment screw and manipulating the caliper or pads somehow?  I just want to be able to move it around the garage...
Title: Re: New (to me!) '77 CB400F - US model
Post by: taysidedragon on October 25, 2018, 04:52:10 PM
They were made in the early days of disc brakes. The designs got better!

The adjuster moves the whole caliper to line it up with the disc. Loosening it won't really help if it's in the right position already.

It sounds like the piston is sticking. Spray some brake cleaner in there and you might be able to free it up just enough to move the bike about. If you're careful, you could use a flat lever to push the piston in a little to free the disc. Even if you free it now it will stick again any time you squeeze that lever.

You will have to check and rebuild the brake caliper anyway at some time. The piston may have corrosion on it and the seal will almost certainly need replacement.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 25, 2018, 05:59:50 PM
Thanks!  I've read here that sometimes the tiny passage in the master cylinder ("compensating port"?) can get blocked, stopping the piston retracting - I'll look at that, then see about the caliper.  It will definitely need attention over the winter, but I'd like to be able to wheel it into my neighbor's basement for winter storage, in the meantime...
Title: Re: New (to me!) '77 CB400F - US model
Post by: SteveD CB500K0 on October 25, 2018, 06:39:28 PM
More common cause of sticking piston is dirt and corrosion.

As long as you own one of these bikes, you will be paranoid about front brake sticking.

I am.




Sent from my iPhone using Tapatalk
Title: Re: New (to me!) '77 CB400F - US model
Post by: K2-K6 on October 25, 2018, 06:58:48 PM
As above,  it's the caliper usually.

They have no, as in zero,  weatherproofing in regards to the seal and overall design so need to be cleaned scrupulously and reassembled to make them work correctly.

They are very simple to work on so don't present a problem in that regard,  but may need a new seal plus careful inspection of the piston to assess for corrosion.  If the piston is corroded they are generally available and not too costly.

As Bryanj's post,  the only way the piston will come out sometimes is to pump it out with the lever while holding in a bucket.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 25, 2018, 07:31:47 PM
Well, poking at the holes in the bottom of the reservoir didn't accomplish anything - when I pulse the brake lever in and out, I can see a little rush of fluid flow back into the reservoir from one of the holes.  The wheel is still stuck, though, so caliper it is.

FYI... new brake master cylinder diaphragm:

(https://www.davidsilverspares.com/graphics/parts/45520300000.jpg)


Mine:

[attach=1]


Obviously no good, and behind that kink there's a rip anyway.  Looks like rebuild kits don't include the diaphragm, either...
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 25, 2018, 09:21:30 PM
Ok, so I thought I'd remove the front wheel so I could squeeze the caliper piston out with the brake lever before dismantling.  Let's see, step one: "remove the speedometer set screw." Easy enough.  Hmm, the recess looks pretty small, what size allen wrench is that?  None of mine fit.  Wait, where's my damn glasses, that doesn't look quite right:

[attach=1]

Wha? Quick forum search for that set screw... oh.  So this is how it's going to be, huh? (sighs...)
Title: Re: New (to me!) '77 CB400F - US model
Post by: Nurse Julie on October 25, 2018, 09:50:50 PM
Oh dear Matt, your introduction to the world of the fubbered fixings has started early on in your project. It will get worse though, so something to look forward too.
Title: Re: New (to me!) '77 CB400F - US model
Post by: K2-K6 on October 25, 2018, 10:02:30 PM
Just go through between the spokes to the two bolts on the back of the caliper to remove it. 

All the fluid is in the outer half (no connection between the two parts at all) so you can unbolt and swing out a little to get access.

It'll become clear when you unbolt it,  there's no bits to catch you out so easy to proceed like this.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 25, 2018, 10:04:18 PM
Oh dear Matt, your introduction to the world of the fubbered fixings has started early on in your project. It will get worse though, so something to look forward too.

Music to my ears!   ;D
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 25, 2018, 10:05:48 PM
Just go through between the spokes to the two bolts on the back of the caliper to remove it. 

All the fluid is in the outer half (no connection between the two parts at all) so you can unbolt and swing out a little to get access.

It'll become clear when you unbolt it,  there's no bits to catch you out so easy to proceed like this.

I'll check it out, thanks!
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 25, 2018, 10:18:20 PM
Just go through between the spokes to the two bolts on the back of the caliper to remove it. 

All the fluid is in the outer half (no connection between the two parts at all) so you can unbolt and swing out a little to get access.

It'll become clear when you unbolt it,  there's no bits to catch you out so easy to proceed like this.

Finally took the time to really look at the whole thing - based on that and what you said about the fluid, I figured, why not just loosen these two a smidgen:

[attach=1]

Worked a treat, wheel spins freely.  I'm wondering if those are the bolts you meant?  Anyway, I'll see about removing the caliper later...
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 25, 2018, 10:26:18 PM
Another little aside: I looked at the drive chain tension - on the center stand, I checked the vertical movement of the lower run of chain, midway between the two sprockets.  The book says 3/4 of an inch.  I wonder if the PO misread it, as the chain currently has 3 inches of movement.  "3/4" and "3" look almost the same, right?
Title: Re: New (to me!) '77 CB400F - US model
Post by: taysidedragon on October 26, 2018, 12:27:53 AM
Another little aside: I looked at the drive chain tension - on the center stand, I checked the vertical movement of the lower run of chain, midway between the two sprockets.  The book says 3/4 of an inch.  I wonder if the PO misread it, as the chain currently has 3 inches of movement.  "3/4" and "3" look almost the same, right?
New chain and sprockets? The list of new parts required starts to grow! 😈
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 26, 2018, 01:28:10 AM
New chain and sprockets? The list of new parts required starts to grow! 😈

Yup!

I read that the tachometer cable set screw is the same as the speedo one - they were right, both screws are equally "chowdered" on my bike...  >:(

I really am going to put it away for the winter, though.  I've got the tank off; I'll pull the carbs and front brake parts, but otherwise it'll have a further rest...
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 26, 2018, 12:18:28 PM
A few other odds and ends...

Not too sure about your driver's footrest position, and it's definitely got the wrong gear lever, it should have two rose joints and a Johnson Rod for adjustment. ... might be worth checking on the rear brake pedal as well, it should have a guard fitted to it to stop your foot rubbing on the clutch cover.

I think the US models are different - here's a couple pics from the OEM owners manual:

[attach=1]

[attach=2]


Float bowl drain screw, yes?

[attach=3]

I tried to open #'s 1 and 4, stuck tight.  I gave up before breaking anything, are there any tricks?
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 26, 2018, 12:22:09 PM
A few years ago, the silencer crack seemed minor, now it's broken all the way 'round, and appears to show sooty signs of leaking on the bottom:

[attach=1]

[attach=2]

Might this be repairable - welded, perhaps?  I know it would be ugly, but function is what counts at this point...
Title: Re: New (to me!) '77 CB400F - US model
Post by: petermigreen on October 26, 2018, 12:41:05 PM
As regards foot brake and gear lever if the US variant is different then only in later modes as mine is American and has the standard items

(https://uploads.tapatalk-cdn.com/20181026/f83ce11484d69baf22967847024730de.jpg)

(https://uploads.tapatalk-cdn.com/20181026/4fcb8e3b0575b1dae424c55dc512012d.jpg)

The carb drain screw shouldn’t be too tight that you can’t release it but caution is required as it is brass and soft as doodoo. I’d get a good fitting screwdriver with a shank that will take a spanner and get extra leverage that way or if really stuck maybe get a pair of grips on them and be prepared to replace with new.

The silencer can be brazed but not welded as far too thin but looking at yours I think replacement is probably the best option.

Keep plugging away they require endurance
Peter


Sent from my iPhone using Tapatalk
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 26, 2018, 01:46:18 PM
As regards foot brake and gear lever if the US variant is different then only in later modes as mine is American and has the standard items

Your statement checks out, based on these paragraphs I found on page 42 in the April 2012 issue of your Classic Bike magazine...

Quote
There is some confusion over model designation. Only the CB400F and the CB400F2 came to the UK. The F1 is a USA- and Canada-only model introduced in 1977. The F model is the original 1975 model year machine with Pillion footrests mounted on the swingarm and an unlined fuel tank in either Light Ruby Red or Varnish Blue. For 1976, the pillion footrests were mounted on a loop coming off the rear subframe and the fuel filler gained a lock, but the model was still called the CB400F in the UK and Europe.

Many US F models were modified with higher 'bars, but the 1977 F1 has a single (rear) stay on the front mudguard, slightly higher handlebars, a locking cover to the fuel cap and foot rests re-positioned a little further forward than on the UK and European models. Rare in the UK.

Mine matches the latter description...


The carb drain screw shouldn’t be too tight that you can’t release it but caution is required as it is brass and soft as doodoo. I’d get a good fitting screwdriver with a shank that will take a spanner and get extra leverage that way or if really stuck maybe get a pair of grips on them and be prepared to replace with new.

I think I'll wait until I remove the carbs to proceed.  I found a thread here where, IIRC, someone sheared the head off, then broke an easy-out in the remainder, then finally cracked the float bowl while trying to remove that drain screw.  So I wondered if it was a common problem, and whether a pre-application of heat and/or penetrating oil might be in order...
Title: Re: New (to me!) '77 CB400F - US model
Post by: K2-K6 on October 26, 2018, 03:22:38 PM
On the carb float bowl screws,  the problem appears to be of corrosion between the two metal parts forming a particularly strong bond which ends up similar to the structural integrity.

As you've posted,  it can easily go wrong or be all but impossible.  Really it's in the realms of experimentation,  maybe if you leave them to soak in something like turpentine/paraffin (think that's kerosene over there)  for a week or so then get them in an ultrasonic cleaner before attempting to undo them?

They may of course be easy but you never know when they were last removed.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 26, 2018, 03:39:05 PM
On the carb float bowl screws,  the problem appears to be of corrosion between the two metal parts forming a particularly strong bond which ends up similar to the structural integrity.

As you've posted,  it can easily go wrong or be all but impossible.  Really it's in the realms of experimentation,  maybe if you leave them to soak in something like turpentine/paraffin (think that's kerosene over there)  for a week or so then get them in an ultrasonic cleaner before attempting to undo them?

They may of course be easy but you never know when they were last removed.

This sounds about right.

I'll basically be readying the bike for winter storage; I was told it last ran really well, but that was two years ago.  So, I'll focus this winter on making sure the fueling components are in good order, and also the front brake components, since I know they're knackered, so I can try to evaluate the rest - safely - on the road in the spring...
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on October 26, 2018, 04:00:28 PM
I will try a basic "how it works"

The piston seal is a square cross section O ring whilst the groove it fits into has a slightly angled base, this means that when the seal is fitted it turns into a "diamond" shape so that only one corner is rubbing on the piston surface.
When the brake is applied the seal "twists" slightly and it is this twist which retracts the piston from the pad. Thus any crap in the groove or on the seal, or tighteness on the piston stops the piston retracting and the brake sticks.

Secondly look at the bracket bolted to the fork with two small bolts at the muguard stay and one big one lower down. The big one has a steel pinthat goes through the swinging part and locates in the top bracket held by the two small bolts, this pivot also gets corroded and the pin pluss hole in the swinging bracket need thourough cleaning and copperslipingso they move very freely. The two bolts you ringed are the ones that split the caliper(no fluid will be lost) the 750 started with bolts you have to undo through the wheel spokes but 550/500/400 do not.

Hope that helps, if in doubt of assembly look at parts book
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 26, 2018, 04:26:28 PM
I will try a basic "how it works"

The piston seal is a square cross section O ring whilst the groove it fits into has a slightly angled base, this means that when the seal is fitted it turns into a "diamond" shape so that only one corner is rubbing on the piston surface.
When the brake is applied the seal "twists" slightly and it is this twist which retracts the piston from the pad. Thus any crap in the groove or on the seal, or tighteness on the piston stops the piston retracting and the brake sticks.

Secondly look at the bracket bolted to the fork with two small bolts at the muguard stay and one big one lower down. The big one has a steel pinthat goes through the swinging part and locates in the top bracket held by the two small bolts, this pivot also gets corroded and the pin pluss hole in the swinging bracket need thourough cleaning and copperslipingso they move very freely. The two bolts you ringed are the ones that split the caliper(no fluid will be lost) the 750 started with bolts you have to undo through the wheel spokes but 550/500/400 do not.

Hope that helps, if in doubt of assembly look at parts book

Thanks for the detailed explaination, Bryanj!  I do understand how the piston interacts with the seals, and why the condition you describe could cause trouble.  I'll study the brackets alongside your explanation, as I'm still not sure why the floating caliper should require manual adjustment.  I'll get there, though...
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 26, 2018, 04:28:27 PM
One of the first things you should buy if you haven't already got some are these.

http://ruggedroads.co.uk/JIS-Screwdriver-Set-Vessel-Megadora-P1-P2-and-P3

A good set of JIS screwdrivers will pay for itself very quickly by not chewing up all those screws on the bike so that you have to buy new ones.

When splitting the caliper be prepared for some real gross looking fluid coming out, I suspect the fluid hasn't been changed since it left Japan.

As for the speedo drive screw, it's clear someone has already attempted to remove it by using a punch, they may have succeeded and just reused the screw, try lightly tapping the screw with a punch and hammer counter clockwise using the existing punch mark and see if it starts to spin out, if your lucky it will.

Thanks, I'll look for some.  Does anyone know if the two "cross-head" screw driver shanks in the OEM tool kit are JIS-friendly?
Title: Re: New (to me!) '77 CB400F - US model
Post by: K2-K6 on October 26, 2018, 05:14:07 PM
These calipers are a bit of a hybrid between manual and hydraulic.

The hydraulic,  obvious as indicated.  The back side hasn't a hydraulic retraction, just done by the little spring until the caliper swing hits the stop screw.  So you set stop screw to give clearance required,  but as the back pad wears you have to "chase " it with adjustment else the pad ends up with too much clearance,  and so increases brake lever travel just to bring pads into contact with disc.

That back part is in essence the same as any cable operated brake.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 26, 2018, 05:45:50 PM
These calipers are a bit of a hybrid between manual and hydraulic.

The hydraulic,  obvious as indicated.  The back side hasn't a hydraulic retraction, just done by the little spring until the caliper swing hits the stop screw.  So you set stop screw to give clearance required,  but as the back pad wears you have to "chase " it with adjustment else the pad ends up with too much clearance,  and so increases brake lever travel just to bring pads into contact with disc.

That back part is in essence the same as any cable operated brake.

So... if everything is working correctly, the adjustment doesn't change how the pads wear relative to each other, just brake lever travel?  I suppose so, but doesn't the piston's movement relative to the seal affect this, too?  Why not just have no spring and no adjustment - let the caliper slide freely and the piston, on one side only, will take up any adjustment needed, like my "modern" bike's caliper?
Title: Re: New (to me!) '77 CB400F - US model
Post by: K2-K6 on October 26, 2018, 06:29:55 PM
Yes,  as you think,  it doesn't affect the wear as that is only the hydraulic force clamping it. And also same forces as the modern ""sliding " single piston type.

It is a bit cock-eyed though (in purist engineering principles) as they've started with a swing geometry so the pads will ultimately wear in a taper, then felt the need to give some sort of assistance plus limit to the assembly. Compared to the straight up design within the engine it does appear to be an odd compromise.

Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 26, 2018, 06:53:48 PM
Yes,  as you think,  it doesn't affect the wear as that is only the hydraulic force clamping it. And also same forces as the modern ""sliding " single piston type.

It is a bit cock-eyed though (in purist engineering principles) as they've started with a swing geometry so the pads will ultimately wear in a taper, then felt the need to give some sort of assistance plus limit to the assembly. Compared to the straight up design within the engine it does appear to be an odd compromise.

Ahh... the pads wear in a taper, too... never thought of that!  Love learning new things...
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 26, 2018, 06:56:17 PM
Thanks, I'll look for some.  Does anyone know if the two "cross-head" screw driver shanks in the OEM tool kit are JIS-friendly?

I'd imagine they are BUT they aren't exactly case hardened so will break eventually, plus the handle is just not up to the job. The ones in the link are magnetic tipped as well, which helps a great deal in getting screws back into confined areas, especially carbs and such.

Yes, the handle leaves much to be desired - in its defense, it is portable!  I just thought I might use them until I get my own better tools...  Too late for the cable set screws...  :(
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on October 26, 2018, 10:38:11 PM
The other reason for the adjuster is that if everything is free vibration between pad and disc can push the piston back through the seal meaning extra lever travel to get the brake to work
Title: Re: Matt's '77 CB400F - US model
Post by: mattsz on October 26, 2018, 10:58:00 PM
I was going to start a new thread, but for now I think I'll carry on with this one, since I'm still only dipping my toes in here...

Brakes:  I removed the caliper, and pumped the piston out before disconnecting the lines.  It was all very unexciting, I think I introduced some air into the system which made the piston only move about 0.5mm per lever pump.  There's some evidence of corrosion, but nothing like as bad as some photos I've seen.  The old fluid was a bit dark but fairly clean, and smelled very strong.  I'll rebuild the master cylinder and caliper this winter.

Here's some photos - I'm posting them as thumbnails that can be clicked on for a bigger view...

Not a very well-lit pic of the caliper's interior, but there's plenty of corrosion where the brake pad rests (at bottom of pic, hard to see), and a wee bit where the piston rides, just inside the rubber seal:

[attach=1]


A couple of the piston, showing some corrosion spots and one proper gouge:

[attach=2]
[attach=3]


The back of the pad, obvious corrosion on the edge to match that inside the caliper:

[attach=4]


The master cylinder - not too bad.  I see two holes only, neither is a pin-sized hole that a guitar e-string might be used to clear:

[attach=5]
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 26, 2018, 11:03:33 PM
I also couldn't budge either the bleed nipple nor the brake line fitting from the caliper - I just left them for now, will try to carefully coax them out later...
Title: Re: New (to me!) '77 CB400F - US model
Post by: K2-K6 on October 26, 2018, 11:20:30 PM
You have to be reallllly careful with those as they will snap off.  Think the common advice on here is to heat them first, but they can be very tricky.

Looks like it was mainly stuck on pad corrosion.  Rain and salted roads make easy work to get that going,  if you're not using in winter then obviously less likely.

Interestingly,  the original manual for the 750 says about the caliper,  to use "silicon sealing grease" all around those pads and the interface with the piston. Presumably they are trying to exclude water as that stuff really resists any ingress. It specifically states "Do not use molybdenum grease,  known as brake grease".
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 27, 2018, 12:30:27 AM
You have to be reallllly careful with those as they will snap off.  Think the common advice on here is to heat them first, but they can be very tricky.

Looks like it was mainly stuck on pad corrosion.  Rain and salted roads make easy work to get that going,  if you're not using in winter then obviously less likely.

Interestingly,  the original manual for the 750 says about the caliper,  to use "silicon sealing grease" all around those pads and the interface with the piston. Presumably they are trying to exclude water as that stuff really resists any ingress. It specifically states "Do not use molybdenum grease,  known as brake grease".

I will be reallllly careful, I promise!

My download copy of the CB350F-400F service manual, which can be found just about everywhere, says "apply a coat of silicone sealing grease to the sliding surface of the calipers when installing the pads."  Doesn't say anything about the pad/piston interface though.  Is this grease heat resistant as well as water resistant?
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 27, 2018, 03:15:18 AM
Yeah it's silicon, they use that stuff to make oven mitts out of these days.

 :-[ I suppose if I had thought about it, I would have made the connection...
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on October 27, 2018, 08:17:09 AM
You will find the hole in the master nearest to the pipe end reduces to the tiny one at the base of the cone you can see. Personaly i would replace that piston, they are not expensive and you only got one neck
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 27, 2018, 10:39:13 AM
Personaly i would replace that piston, they are not expensive and you only got one neck

I will replace it - only one neck, as you say!  Are there new pistons/pads made from materials that won't corrode as much, or at all?
Title: Re: New (to me!) '77 CB400F - US model
Post by: hairygit on October 27, 2018, 11:09:19 AM
Someone your side of the pond used to make them from phenolic resin, but I can't remember who, someone will.

Sent from my X6pro using Tapatalk

Title: Re: New (to me!) '77 CB400F - US model
Post by: taysidedragon on October 27, 2018, 11:16:00 AM
Personaly i would replace that piston, they are not expensive and you only got one neck

I will replace it - only one neck, as you say!  Are there new pistons/pads made from materials that won't corrode as much, or at all?
There are stainless steel pistons available, the pads are not so much of a problem.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 27, 2018, 11:38:00 AM
Just did a quick "phenolic" search - the name Kevin Hunter appears a couple of times.  Anyone with experience on this OEM/phenolic/stainless question care to chime in?

EDIT: Kevin Hunter hasn't posted on that forum in many years...
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on October 27, 2018, 12:50:40 PM
Look up roger7500_1 on ebay. He is in UK but gives you some idea
Title: Re: New (to me!) '77 CB400F - US model
Post by: Seabeowner on October 27, 2018, 01:29:21 PM
Just did a quick "phenolic" search - the name Kevin Hunter appears a couple of times.  Anyone with experience on this OEM/phenolic/stainless question care to chime in?

EDIT: Kevin Hunter hasn't posted on that forum in many years...
Godffeys's garage in the States. I always used stainless as they are cheaper, but they are heavier.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 27, 2018, 06:59:24 PM
I guess I need to brush up on the firing order and workings of this engine.  Is there a crank position where all the valves are closed?  I'd like to leave the engine in that condition, if possible, when I put it to bed for the winter...
Title: Re: New (to me!) '77 CB400F - US model
Post by: hairygit on October 27, 2018, 07:20:11 PM
Short answer, no! The only way to get all valves closed is lift the rocker cover, but probably not a good idea.

Sent from my X6pro using Tapatalk

Title: Re: New (to me!) '77 CB400F - US model
Post by: taysidedragon on October 27, 2018, 10:38:21 PM
Short answer, no! The only way to get all valves closed is lift the rocker cover, but probably not a good idea.

Sent from my X6pro using Tapatalk
Or slacken off all the tappets so they are not pushing down on the valves.
Have to do that before taking off the cam cover anyway. 🔧👍
Title: Re: New (to me!) '77 CB400F - US model
Post by: ted_paper on October 28, 2018, 08:50:45 AM
Hi,
I have Kevin's phenolic brake piston fitted for the last seven years and have had no problems with sticking or anything else.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 29, 2018, 03:22:36 PM
I had a few minutes to kill this morning...

Battery: I topped up the cells with distilled water, then left it overnight on my 0.75 amp tender; it reached about 6V (it's not meant to charge a dead battery anyway).  Over the next couple of days, I managed to get it charged to about 13V using a bigger car charger (set on 2A) followed by a topping up with the 0.75A tender.  But when I reconnected it and turned the key, I got nothing.  I connected a volt meter, with the key off it read about 10V, but as soon as I turned the key, volts dropped literally to zero, so I'd say the battery is shot.

I removed the plugs - last run two years ago:

[attach=1]


The oil on the dipstick looks very clean and clear.  The kick start lever easily turned the engine over, by hand.  I added a teaspoon or so of oil to each cylinder, turned the engine over by hand a few times, then I figured I'd try to check the oil pressure by spinning the engine.  I hooked up a spare battery pack... remember three years ago the PO said the starter didn't work when it was wet?  Well, it's not wet now, but it still doesn't work.  The start relay buzzes loudly, though, so I'm thinking that should be a simple fix.  The starter button feels kind of sticky anyway, so I'm just as happy not to try to use it and have it stick on with the starter turning.  No big surprises or concerns there.

I kicked the engine over manually, still without the plugs in, key on and powered up - after about 20 kicks, the oil pressure light went out, and stayed out for about 20 seconds.  After it came back on, one or two more kicks turned it off again for a few seconds.  10 or so kicks turns the light off for about 20 seconds.  Does this seem like a reasonable non-running oil pressure test?

When I change the oil again before storage, is it enough to try to circulate it manually, or should I see about bypassing the starter relay to properly crank the engine?
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 29, 2018, 03:33:51 PM
Hi,
I have Kevin's phenolic brake piston fitted for the last seven years and have had no problems with sticking or anything else.

Thanks for that info!  But as near as I can tell, Kevin is not in the USA and is no longer supplying parts...
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on October 29, 2018, 03:55:24 PM
Oil pressure sounds good, if the oil looks clean and does not smell of petrol i would leave it in there till next year when you are ready to get it going again.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 29, 2018, 03:58:43 PM
Oil pressure sounds good, if the oil looks clean and does not smell of petrol i would leave it in there till next year when you are ready to get it going again.

Thanks!  I was thinking of changing the oil as cheap insurance, since I don't know how many miles or how much time went by on the current oil before the bike was stored for two years.  I'll sniff around for fuel in the oil...
Title: Re: New (to me!) '77 CB400F - US model
Post by: Nurse Julie on October 29, 2018, 04:22:25 PM
If oil does not smell of fuel, i would also leave what's in there over winter. If you are not running the engine, the oil isn't going to break down, it's just coating all the surfaces. Plugs look fine.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 29, 2018, 04:25:49 PM
So no worries about moisture or acids in dirty oil to contaminate or oxidize engine internals?
Title: Re: New (to me!) '77 CB400F - US model
Post by: Nurse Julie on October 29, 2018, 04:30:14 PM
Air, not oil or water causes oxidation. As long as the oil is all around the engine internals, it will do more good than harm, regardless of the state of the oil.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 29, 2018, 05:05:21 PM
Huh.  Every resource I find concerning storage preparation suggests changing the oil before storage to avoid corrosive damage from oil-borne acids and carbon deposits.

I thought a few new quarts of oil would be smart, due to the unknown condition and age of the current oil.  But maybe there's no point if the only way to properly circulate it is to run the engine?
Title: Re: New (to me!) '77 CB400F - US model
Post by: Nurse Julie on October 29, 2018, 05:16:46 PM
I must admit i have never done any research of what process to carry out to store a bike. It is such a short term storage,  taking the bike off the road for the winter, i don't even consider it to be storage really. I have a bike here of my own, a CB750/4, that has not been in the road for 3 years, i didn't change the oil or do anything else. Everything will be checked, changed and serviced before going on the road. No point in doing it before a few weeks lay up and again after.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 29, 2018, 05:20:35 PM
All good Julie!  This one will be sitting for six months, and with so many unknowns, and my lack of experience with these things, I've been making my plans on the side of caution...
Title: Re: New (to me!) '77 CB400F - US model
Post by: Nurse Julie on October 29, 2018, 05:26:20 PM
Understand Matt 👍. All our old Hondas that we ride came off the road last week and will not be ridden until April next year at the earliest and they were just parked up with no prep. I worry a lot more about rust forming on chrome parts than anything to do with engine internals.
Title: Re: New (to me!) '77 CB400F - US model
Post by: Nurse Julie on October 29, 2018, 05:33:02 PM
Out of interest Matt, what is the winter weather like where you live?
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 29, 2018, 05:57:10 PM
Out of interest Matt, what is the winter weather like where you live?

[attach=1]

[attach=2]

I dare you to click on them...
Title: Re: New (to me!) '77 CB400F - US model
Post by: Nurse Julie on October 29, 2018, 06:01:04 PM
Blimey, I was expecting you to say wall to wall sunshine and a constant 26°c 🤣🤣🤣
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 29, 2018, 06:06:25 PM
Blimey, I was expecting you to say wall to wall sunshine and a constant 26°c 🤣🤣🤣

Yes - 26º Fahrenheit! :(
Title: Re: New (to me!) '77 CB400F - US model
Post by: Nurse Julie on October 29, 2018, 06:16:58 PM
Blimey, I was expecting you to say wall to wall sunshine and a constant 26°c 🤣🤣🤣

Yes - 26º Fahrenheit! :(
😰😰😰😰😰
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on October 29, 2018, 06:36:38 PM
Buy wd 40 by the 5ltr can withe the pump type sprayer and cover everything with it!
Title: Re: New (to me!) '77 CB400F - US model
Post by: petermigreen on October 29, 2018, 06:40:02 PM
ACF50 made for that job
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 29, 2018, 06:47:28 PM
I have plenty of ACF50 - the first time I used it, it sprayed on like a gel and what a pain to clean it off again in the spring!  I wipe the stuff on now.  Maybe if I warm the spray bottle first...
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on October 29, 2018, 06:55:29 PM
Thats why i use WD, it comes off with engine degreaser
Title: Re: New (to me!) '77 CB400F - US model
Post by: Laverda Dave on October 29, 2018, 09:27:07 PM
I've given up with using all the potions to try and stop corrosion during the winter. I now use a dehumidifier 24/7 when the temp gets really cold and dew starts appearing on the bikes in the garage. The dehumidifier I use is a Ruby Dry. I've checked it's consumption on the smart meter and it's 4p/hr on its lowest setting which is plenty good enough for my pre-cast concrete panel but now fully insulated double garage. First time I used the dehumidifier was last year and the bikes suffered no corrosion at all. Added bonus was the garage was a constant 7c but felt warmer as the air was dry even when outside was 2c and damp so it was warm enough to work in (with some extra layers!).
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 29, 2018, 09:42:17 PM
I've given up with using all the potions to try and stop corrosion during the winter. I now use a dehumidifier 24/7 when the temp gets really cold and dew starts appearing on the bikes in the garage. The dehumidifier I use is a Ruby Dry. I've checked it's consumption on the smart meter and it's 4p/hr on its lowest setting which is plenty good enough for my pre-cast concrete panel but now fully insulated double garage. First time I used the dehumidifier was last year and the bikes suffered no corrosion at all. Added bonus was the garage was a constant 7c but felt warmer as the air was dry even when outside was 2c and damp so it was warm enough to work in (with some extra layers!).

Sounds ideal!  But my garage isn't insulated, and my wife's car comes in and out all winter long.  But, my neighbor will be storing this bike for the winter: at one point he said "basement," and at another he said "garage," so I'm not sure if it will be in a heated space or not - although I'm guessing not.  I think I'm just going to leave it dusty for this winter, I don't see how it could hurt - maybe wipe the chrome and already surface-rusted frame bits with some ACF-50 for grins and call it good.  I'll have the gas tank and carbs in my heated basement for the winter...
Title: Re: New (to me!) '77 CB400F - US model
Post by: K2-K6 on October 30, 2018, 10:20:39 AM
The oil question for storage.  I've wondered about this, as you do,  thinking that it's better to store it with new oil pumped round it but not run at all.

The issue for used oil is that if it contains much in the way of combustion byproducts,  then the one that really concerns us is sulphuric acid. This should be reduced with later fuels that have reduced sulphur content,  but acid is still there in a form that's not much good for the components,  the new oil is chemically buffered as I understand it to try and keep it near to Ph neutral.  New oil left in for winter wouldn't have to be changed when getting it out of storage,  you'd still only have to do it once.

But, I was looking at a 750 recently that had at some point been stored for longer period. One of the concerns was a clear corrosion affect on the crank bearing shells,  you could see almost that spidery creep you get from corrosion and feel it like a very fine sandpaper with your finger nail. I can't see what else would cause this so tentatively attached it to oil condition when put into storage.

It is of course this acid in the exhaust gasses that has initiated the damage to the exhausts over the years. Any extended running on choke just exaggerates it which is another good reason why you'd not want to run it at all when layed up as you can't get the exhaust hot enough to dry out.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on November 05, 2018, 12:31:22 AM
I started work on pulling the carbs today - following this basic advice:

I had my carbs off recently. Getting them off is simple but putting them back on can be a pain, or rather getting the air box rubbers back onto the carbs can be a pain - if they have age hardened.

Undo fuel hose from tap and remove petrol tank

Undo / remove throttle cables from carbs

Loosen off clamps on the rubbers between carbs and head / carbs and air box

Pull air box back off carbs and remove air box rubbers then pull carbs back from the head rubbers

You should have enough room to get the carbs out to the side now. I leave all petrol lines and overflows connected to the carbs.

I ended up buying new air box rubbers From DS to make refitting easier after using a heat gun previously to soften up the hardened rubbers.

There doesn't seem to be enough room to do all this - is it just because the rubbers have hardened up and are not flexible?  I've loosened or removed the clamps from both sides of the carbs and the big air filter-to-airbox clamp- everything wiggles around now, but I can't release anything without running out of movement.  Should the rubbers between the airbox and carbs actually be removable from both of those items?  They seem really stuck, I'm afraid I'll crack the airbox if I force anything.

Any further advice, or just persevere?
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on November 05, 2018, 12:35:20 AM
I've read through the Clymer manual, cover to cover - leaves a lot to be desired!  Lots left out, plenty of mistakes (mis-labeled diagrams, removal process descriptions that mention unidentified parts with names that aren't found anywhere else, etc).  I was thinking of trying the Haynes book, but Haynes publishes the Clymer book, too, so maybe there's nothing to be gained?
Title: Re: New (to me!) '77 CB400F - US model
Post by: AshimotoK0 on November 05, 2018, 07:51:41 AM
I've read through the Clymer manual, cover to cover - leaves a lot to be desired!  Lots left out, plenty of mistakes (mis-labeled diagrams, removal process descriptions that mention unidentified parts with names that aren't found anywhere else, etc).  I was thinking of trying the Haynes book, but Haynes publishes the Clymer book, too, so maybe there's nothing to be gained?


J
CB400F PARTS

https://www.dropbox.com/s/u51uf0p1dv6m29q/Honda%20CB400%20F%20Parts%20Manual.pdf?dl=0

CB400F PARTS USA Searchable

https://www.dropbox.com/s/j0hysqub5jsfg46/400-4%20Part%20List%201975%20searcheable.pdf?dl=0


CB350/400F SHOP MANUALWORKSHOP

https://www.dropbox.com/s/1n3w5433jkph228/350F%20400F%20_4%20Shop%20Manual.pdf?dl=0

CB350F Part Manual

https://www.dropbox.com/s/7pieydvznvy7nhp/CB350_F_F1%20Full.pdf?dl=0

CB400F DEALER SETUP INSTRUCTIONS .. RARE !!

https://www.dropbox.com/s/ewl1d9td0nhxeya/CB400_set-up_man.pdf?dl=0
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on November 05, 2018, 10:23:01 AM
AshimotoK0 - many thanks for those links! I actually have all those downloads already.  I like to have print materials to read and work from, so I purchased the Clymer.  I may try to print out the "official" Honda manual, or sections of it at least.

I must admit the Kawasaki service manual for my 2000 W650 is great!  Lots of information, great diagrams and clear photos... but of course, there's still errors and omissions... nothings perfect, I guess!  :(
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on November 06, 2018, 12:15:56 AM
Stacking up questions here...

I've got one key, "opens" everything.  It's very basic, by the looks of its cutouts.  I could probably buy a blank and file a new one freehand in about a minute.  But, does the 3-digit number on the key imply I might be able to order a new one?  Or, perhaps might I have been able to in 1977?
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on November 06, 2018, 08:18:03 AM
Yes there are a few suppliers working to number
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on November 06, 2018, 09:28:04 AM
Does the number suggest a certain key "blank" size or shape, or does it actually tell the cut pattern?  I've seen some other key threads, usually involving fuel tank access or ignition problems, with key numbers mentioned that have more than just three digits, and usually some letters as well...
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on November 06, 2018, 09:44:31 AM
The older Hondas used to start with a T or H but later ones just have numbers and can be 3 or 4. I think there is a firm called something like "hondakeys" on ebay who should be able to tell you if yhe number is ok. In theory there should be a number on the seat lock if you take it off and also on the ignition barrell if you take that off.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on November 06, 2018, 09:45:46 AM
Thanks Bryanj!
Title: Re: New (to me!) '77 CB400F - US model
Post by: zebedee85 on November 07, 2018, 02:27:36 PM
The rubbers connecting the carbs to the airbox should be nice and squidgy. If they're not then you may need to remove the airfilter assembly to give yourself enough space to wiggle the carbs free, this is the case on the 550f. warm them up, try lots of penetrating fluid around the rubbers (someone may chip in and not recommend this, but i find it works)

i found the 400f carbs quite tough even with good movement in the airbox rubbers, lots of easing, patience and sore hands.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on November 07, 2018, 02:58:57 PM
Thanks zebedee85!

The rubbers are pretty hard and "unforgiving."  If by the airfilter assembly, you mean the box the filter lives in - unless I'm mistaken, it seems like removing that is a major job due to all the electrical components mounted to the left side of it.

I was able to pull the airbox-side rubbers from the carbs, but I still can't see how to gain enough room to pull the carbs away from the engine-side rubbers.  Maybe some WD-40 would be safe to try - not to gain room, obviously, but to ease the movement...

I'll keep at, my hands aren't all that sore yet, so obviously I'm still not doing it quite right...  ;)
Title: Re: New (to me!) '77 CB400F - US model
Post by: K2-K6 on November 07, 2018, 03:31:25 PM
I can't find it with search on here, but I thought that the more 400 experienced owners may unbolt the airbox and just move it back in the frame to allow more room.

Your hands do end up a bit scrappy doing things like this though  :)

Any heat you can get into them helps with flexibility.
Title: Re: New (to me!) '77 CB400F - US model
Post by: zebedee85 on November 07, 2018, 04:00:54 PM
the carbs are not seated that far into the manifold-side rubbers, there is 'just' enough clearance to pull the carbs back, push them down and then pull out - i think the side you pull them out matters too if i recall correctly.
Title: Re: New (to me!) '77 CB400F - US model
Post by: Nurse Julie on November 07, 2018, 05:11:11 PM
I find it easiest to remove the air filter, undo the big clamp on the air duct guide, remove air duct guide by pushing the guide back into where the air filter was. Loosen all clamps.Pull back on cleaner chamber, this will remove the rubbers attached to the air chamber from the carbs. Then remove the cleaner chamber completely from the off side of the bike. The carbs then pull out of the carb insulators. Remove complete carb bank from off side of bike. Reverse to refit.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on November 07, 2018, 05:36:57 PM
I find it easiest to remove the air filter, undo the big clamp on the air duct guide, remove air duct guide by pushing the guide back into where the air filter was. Loosen all clamps.Pull back on cleaner chamber, this will remove the rubbers attached to the air chamber from the carbs. Then remove the cleaner chamber completely from the off side of the bike. The carbs then pull out of the carb insulators. Remove complete carb bank from off side of bike. Reverse to refit.

This is the approach I'm trying - but I can't seem to get the air duct guide to budge.  Nothing seems to move in there, and it all feels like hard plastic rather than rubber.  I'll investigate further...
Title: Re: New (to me!) '77 CB400F - US model
Post by: Nurse Julie on November 07, 2018, 06:09:26 PM
It's just the metal tube that links the  two that you need to push through. It can be a bit tight. Have you undone the really big clamp holding the rubber around it ?
Title: Re: New (to me!) '77 CB400F - US model
Post by: Nurse Julie on November 07, 2018, 06:14:52 PM
[attachimg=1]

[attachimg=2]
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on November 07, 2018, 06:24:15 PM
It's just the metal tube that links the  two that you need to push through. It can be a bit tight. Have you undone the really big clamp holding the rubber around it ?

I was going to write: Yes - all clamps are loosened, the big one removed completely.  I think my main problem is that the rubber bits are hardened up - I'll try to warm them up and maybe give them a massage.  Oh boy, please don't tell my wife about this!

But now I see your very helpful photo - the rubber that holds the air duct guide feels almost like the plastic of the air chamber, so I expect resistance.  But I'll do my best to work the guide backwards out of the rubber seal.

Part of my problem was, the parts diagram make is look like the air duct guide goes between the rubber seal and the air chamber - rather than the air filter cavity side, which your photo clearly shows.  Do you ever use any kind of lubricant to help ease parts along old rubber?
Title: Re: New (to me!) '77 CB400F - US model
Post by: Nurse Julie on November 07, 2018, 06:26:40 PM
A smear of Red Rubber Grease helps.
Title: Re: New (to me!) '77 CB400F - US model
Post by: K2-K6 on November 07, 2018, 07:05:45 PM
It's all right,  Julie is a real nurse and you can classify this as medical intervention  ;D

As with all medical records they don't have to be disclosed to third party  ;) nobody will know  :) :) :)
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on November 07, 2018, 08:00:09 PM
A smear of Red Rubber Grease helps.

Not sure how I'll work it in during removal, but I'll see what happens!

It's all right,  Julie is a real nurse and you can classify this as medical intervention  ;D

As with all medical records they don't have to be disclosed to third party  ;) nobody will know  :) :) :)

My wife always seems to know when I've been giving massages to motorbikes.  Maybe I should start washing my hands?
Title: Re: New (to me!) '77 CB400F - US model
Post by: Nurse Julie on November 07, 2018, 08:55:27 PM
A smear of Red Rubber Grease helps.

Not sure how I'll work it in during removal, but I'll see what happens!

It's all right,  Julie is a real nurse and you can classify this as medical intervention  ;D

As with all medical records they don't have to be disclosed to third party  ;) nobody will know  :) :) :)

My wife always seems to know when I've been giving massages to motorbikes.  Maybe I should start washing my hands?
Sorry, I misunderstood, you won't get grease in to help removal. But it helps when refitting. If you have a tin if silicone spray with a thin tube out of the nozzle, you may be able to get some of that in to help removal.You could also use a very large flat blade screwdriver, or similar, to get behind the lip of the duct guide and prize it backwards.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on November 07, 2018, 08:57:09 PM
Thanks Julie - silicone spray may help with the removal... and with keeping my hands clean, too!
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on November 07, 2018, 11:02:10 PM
Result!  Once I found the lip in the rubber seal that holds the flared rim of the air duct guide, I was off to the races.  The guide came out pretty easily, then I had to remove the rubber seal, then the other rubber seal, in order to get the air chamber out, followed by the carbs.

With the carbs off the bike, I was able to carefully loosen all four float bowl drain screws.  Dry, of course, and the threads were a little powdery.  I removed one of the float bowls (all four screws were just barely tightened, almost finger-tight - surprising) and... well, I've seen worse.  But a cleanup is in order.  Pics (click to zoom in):

inside the bowl - loose powdery stuff in the bottom:

[attach=1]


The floats, etc:

[attach=2]


The main jet (?) and the spring holder (which has no name or part number in my parts list):

[attach=3]


Yummy stuff which fell out of the float bowl when I tipped it over:

[attach=4]


I'll put the bike to bed now, with oiled rags stuffed in the intakes and silencer, and some oil in the cylinders.  I have the carbs and the front brake bits to work on this winter...
Title: Re: New (to me!) '77 CB400F - US model
Post by: Nurse Julie on November 07, 2018, 11:08:20 PM
Jet retainer clip 😀😀😀 We'll done Matt, you git there in the end. It's easy once you know how these things come apart.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on November 07, 2018, 11:18:59 PM
Easy once you're told how these things come apart!  Thanks Julie!

ps: it's getting late, go to bed!
Title: Re: New (to me!) '77 CB400F - US model
Post by: Nurse Julie on November 07, 2018, 11:27:46 PM
 💤 💤 💤
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on November 08, 2018, 01:06:06 PM
I just discovered that there's supposed to be a retaining spring holding the air filter in place - missing on this bike, the filter is just sitting in the box.  I wonder if it's been ridden that way for any length of time?

That, and the 3-1/2 inches of drive chain slack...
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on November 08, 2018, 01:13:30 PM
Sounds about right
Title: Re: New (to me!) '77 CB400F - US model
Post by: SteveD CB500K0 on November 08, 2018, 01:18:38 PM
Rich (RGB750) made a batch of these.

He may have some left...

Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on November 08, 2018, 01:38:57 PM
Dave Silver lists them - shipping costs double the price, though, becomes a $20 piece of bent wire...  I might even try making my own...
Title: Re: New (to me!) '77 CB400F - US model
Post by: Nurse Julie on November 08, 2018, 01:41:24 PM
Rich (RGB750) made a batch of these.

He may have some left...
Different type to what Rich made on the CB400/4's Steve.....but, if he has made some for the 400, I need one.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on November 08, 2018, 01:44:07 PM
Rich (RGB750) made a batch of these.

He may have some left...
Different type to what Rich made on the CB400/4's Steve.....but, if he has made some for the 400, I need one.

Julie - are you running without one?  Have you "shimmed" the filter tight, or come up with some other method of sealing it?
Title: Re: New (to me!) '77 CB400F - US model
Post by: Nurse Julie on November 08, 2018, 02:08:12 PM
Rich (RGB750) made a batch of these.

He may have some left...
Different type to what Rich made on the CB400/4's Steve.....but, if he has made some for the 400, I need one.

Julie - are you running without one?  Have you "shimmed" the filter tight, or come up with some other method of sealing it?
Well Matt, its a bit of a mystery, I did have one but when I was looking in there the other day, its not there now. I can only think I didn't replace it when I put the bike back together, it must be here somewhere. Anyway, a clothes peg wedged down each side, at the back, will do the job just as well I'm sure.
Title: Re: New (to me!) '77 CB400F - US model
Post by: billywingnut on November 08, 2018, 09:51:37 PM
Hi Mattzs,
I bought  a '75 UK model 2 years ago  the tax disk on the bike was for dec 1998. I decided to restore it to ride and not to concourse. I knew it was going to be costly and take time to go thro' it.
Expect to spend £2k. It had to be reliable and safe.
Here's what i did. The carbs, fit new kits and cleaned them, the air box is a pig to get back on. Overhauled the front brake with master cylinder, lines and pads, the disk was ok put on new rear brake shoes.
New wheel bearings back and front, new spokes front and rear, front wheel rim, tyres and inner tubes. Changed the Headstock bearings and fork seals. At this point I decided to strip down the bike completely. It had 34k on the clock. I did a compression test and found no. 2 very low so stripped the engine down and fitted new rings, The cylinder head was a pig to get off as two nuts are open to the  elements these were rusted solid. I replaced the cam chain and cam chain tensioners.
The primary drive chain, chain and sprokets, lapped the valves etc. all the bearings appeared to be in good order but you have to replace all the oil seals, The is an excellent you video on stripping down the engine.  The tank was the wrong colour ( yellow)  but in
good condition so I lined the tank and resprayed it using 2part  rattle cans and it sets hard and looks the part, yours being the US model has the strange filler cap I replaced the petrol filter and fuel lines. The exhaust is the original and like all bright work in serviceable condition. I finally got it on the road in May this year and for safety I took it and had it MOD't which it passed . It's a pleasure to ride, not the fastest bike on the block and you have to rev them.
 I removed the cover from the wiring loom and removed bodges and wiring that didn't belong and checked every connector, you can buy jap connectors so I replaced the lot.
Being a 'mature' rider  at 71 I had the time and patience to sort it. I could easily have spent another £1000 on the engine on a rebore
and replacement head as there is some burnt sections, you have to make a judgment as to how far to go with your restoration. I used only basic tools. Good luck with your 400f 4
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on November 08, 2018, 10:26:29 PM
Hi billywingnut -

Wow, thanks for the detailed list!  Compression test, I knew I forgot something!  Oh well, it can wait a few more months.  Still not sure how I'm going to proceed with this - I can't see doing a concours restore, as I don't have the tools, the skills, the time, or the money - hmm, did I miss anything?  The PO says the bike is in good shape, but I'm finding more and more little things that make me wonder why he thinks so.

Another thing I just discovered - the rear fender is badly cracked where one of the upper bolts holds the monstrous tail light.  Wondering about whether to just try to structurally repair these items - seems silly to spend money to renew only a select few bits.

Glad the price was right (free!). More to think about...
Title: Re: New (to me!) '77 CB400F - US model
Post by: Laverda Dave on November 08, 2018, 10:47:44 PM
Matt, do yourself a big favour and buy yourself a 3ltr ultrasonic cleaner. In the UK they cost about £75. Considering it costs £25 per carb for commercial ultrasonic cleaning and there are four of them on a 400/4 buying your own cleaner will pay for itself the first time you use it! You will need to buy a special carb cleaner to add to the water and this costs about £13/litre, you dilute this 1 part to 10 parts water. The added advantage of doing it yourself is you can take the carbs apart in the morning and have them back together in the evening (assuming you have the carb rebuild kits handy). Sending them away to be cleaned just adds time and money when you could be doing something else.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on November 08, 2018, 11:07:41 PM
Thanks for the advice, Laverda120 - I'll look into that.  I don't have a lot of space, but it looks like a 3-liter unit isn't very big - smaller than 1 cubic foot?  I know a few people who may have such a thing and would be willing to help out, perhaps for free or for the cost of the cleaning fluid, worth asking around...
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on November 09, 2018, 07:32:30 PM
I examined the tires more closely.  They're both Dunlop D404, 100/90-18 front, 120/90-18 rear.  Both were made around this time of year - in 2008.  They have a reasonable amount of tread left on them, but they seemed kind of... shiny?  A bit hard?  The rear sidewalls are clear, but the front has some age cracking - so no riding on these babies!  I'll call them "storage tires!"  So, new tires added to the list...

This free motorcycle is getting expensive!  ;D
Title: Re: New (to me!) '77 CB400F - US model
Post by: Nurse Julie on November 09, 2018, 08:19:47 PM
This free motorcycle is getting expensive!  ;D

Just doing the essentials and making sure it is safe need not cost a fortune Matt. Now, if you want to restore it to concours, well, that's a totally different story 😀😀😁
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on November 09, 2018, 09:22:09 PM
This free motorcycle is getting expensive!  ;D

Just doing the essentials and making sure it is safe need not cost a fortune Matt. Now, if you want to restore it to concours, well, that's a totally different story 😀😀😁

My intention is to get it working safely and well.  So far: New tires, new battery, probably new chain (and possibly sprockets to match) - that's just consumables!  Who knows what we'll find when we start digging in? (https://advrider.com/f/styles/advrider_smilies/ne_nau.gif)
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on November 10, 2018, 02:03:06 PM
The is an excellent you video on stripping down the engine.

A quick youtube search yields a series of videos posted by "too old to die young" - do you have any specific information about the video you recommend?
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on November 11, 2018, 09:16:19 PM
Getting waaaay ahead of myself here...

I bought a set of old Shoei hard luggage to mount on my Kawasaki W650 - but after getting them in hand and looking at them and trying to sort out how to mount them, I'm not convinced they're right for the bike.  But... maybe for the CB?  At a glance, it looks like the mounting hardware might fit a bit better.  The pie-plate turn signals are in the way and would have to go; the bags have what looks like lights, but they're just lenses with no wiring or sockets of any kind, so that would take some sorting.  Plus, I don't think I would want the bags mounted all the time, so I'd have to have some permanent lights on the bike anyway.

Like I said, waaaay ahead of myself!  ;D

[attachimg=1]
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on November 16, 2018, 12:43:16 AM
If I run into specific issues, I'll ask separately, but I'll add general thoughts here...

I've been digging through the archives, and I found a 2017 thread started by Nurse Julie about idle issues - this was before her epic engine rebuild!

http://www.sohc.co.uk/index.php/topic,12977.0.html (http://www.sohc.co.uk/index.php/topic,12977.0.html)

In that thread, she said:

Quote
as Trig said before, the engine does need some internal work done as she has oil vapour in the airbox.

So I'm wondering - does oil vapo(u)r in the airbox always suggest the need for engine work?  And, what does it look like?  In my bike the little breather foam filter beneath the air filter is disintegrating, and is quite oil-soaked.  The air box around it is damp with oil, as is the bottom of the primary air filter.  It this an indicator that internal engine work is definitely in my future?

[attach=1]

[attach=2]

[attach=3]
Title: Re: New (to me!) '77 CB400F - US model
Post by: taysidedragon on November 16, 2018, 11:42:11 AM
It's hard to be sure because you don't know how long it has been since the oil trap was last cleaned out. It could have built up over a long period of time.
If it built up quickly it could indicate engine wear, probably piston rings/rebore or valve wear.
Title: Re: New (to me!) '77 CB400F - US model
Post by: zebedee85 on November 16, 2018, 12:04:59 PM
this can happen if the oil is ever overfilled as well.

if your air box doesn't fill with oil quickly, you don't encounter blue smoke, your cam chain can be adjusted via an non-seized adjuster mechanism and any head oil weeps remain insignificant I'd leave it alone until it was worth pulling apart.
Title: Re: New (to me!) '77 CB400F - US model
Post by: Nurse Julie on November 16, 2018, 03:41:33 PM
No point thinking about engine rebuilds until you know how long the trap and air filter box hasn't been cleaned for. Mine filled with oil vapour quite quickly due to internal damage the engine had sustained previously causing raised crank pressure. Give it all a good clean out, fit new foam (make your own out of a kitchen foam scratchy thingy) and air filter,ride it and observe. Even if there is nothing particularly wrong with your engine, its an old engine so internal wear is to be expected but oil vapour doesn't give conclusive evidence that there is a problem that needs immediate attention. As has already been pointed out a combination of oil vapour and blue smoke would give more of an indication that there may be a problem.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on November 16, 2018, 04:07:34 PM
Thanks all!  I wish I'd paid more attention when I rode it 3 years ago - it has only a few hundred miles more since then.  But I wouldn't have known what to pay attention to anyway, as far as noises and such on these engines go.  Blue smoke is universal, however!  I don't recall any at the time...

I won't worry about it now, just a fact-finding mission, if you will...
Title: Re: New (to me!) '77 CB400F - US model
Post by: paul G on November 16, 2018, 04:29:14 PM
No point thinking about engine rebuilds until you know how long the trap and air filter box hasn't been cleaned for. Mine filled with oil vapour quite quickly due to internal damage the engine had sustained previously causing raised crank pressure. Give it all a good clean out, fit new foam (make your own out of akitchen foam scratchy thingy) and air filter,ride it and observe. Even if there is nothing particularly wrong with your engine, its an old engine so internal wear is to be expected but oil vapour doesn't give conclusive evidence that there is a problem that needs immediate attention. As has already been pointed out a combination of oil vapour and blue smoke would give more of an indication that there may be a problem.

Tut Tut modern day women ;) it's a scourer
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on November 16, 2018, 04:32:22 PM
Tut Tut modern day women ;) it's a scourer

Wait... should I be including the yellow soaker-upper do-dad with the scratchy thingy?
Title: Re: New (to me!) '77 CB400F - US model
Post by: Nurse Julie on November 16, 2018, 04:36:33 PM
No point thinking about engine rebuilds until you know how long the trap and air filter box hasn't been cleaned for. Mine filled with oil vapour quite quickly due to internal damage the engine had sustained previously causing raised crank pressure. Give it all a good clean out, fit new foam (make your own out of akitchen foam scratchy thingy) and air filter,ride it and observe. Even if there is nothing particularly wrong with your engine, its an old engine so internal wear is to be expected but oil vapour doesn't give conclusive evidence that there is a problem that needs immediate attention. As has already been pointed out a combination of oil vapour and blue smoke would give more of an indication that there may be a problem.

Tut Tut modern day women ;) it's a scourer
Ok Paul, it's Friday, i can't remember the name of anything by Friday 😭😭😭
Anyways, here's mine.[attachimg=1]
Title: Re: New (to me!) '77 CB400F - US model
Post by: taysidedragon on November 16, 2018, 04:37:43 PM
Tut Tut modern day women ;) it's a scourer

Wait... should I be including the yellow soaker-upper do-dad with the scratchy thingy?

Of course! It's handy for cleaning your paintwork when you're out for a ride.  ;) :o ???
Title: Re: New (to me!) '77 CB400F - US model
Post by: paul G on November 16, 2018, 04:38:43 PM
You could sell that as an unused gift ;D
Title: Re: New (to me!) '77 CB400F - US model
Post by: Nurse Julie on November 16, 2018, 05:32:17 PM
You could sell that as an unused gift ;D
It was given to me by someone as an unusual gift Paul....i will give you only one guess who that was !!! 😏😏😏
Title: Re: New (to me!) '77 CB400F - US model
Post by: paul G on November 16, 2018, 10:41:42 PM
 ::) ::) ::) ;D
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on November 16, 2018, 11:22:45 PM
Julie - that's much thicker than my original disintegrating one - any reason for that?  Or for keeping the scratchy bit?
Title: Re: New (to me!) '77 CB400F - US model
Post by: Nurse Julie on November 16, 2018, 11:34:26 PM
Julie - that's much thicker than my original disintegrating one - any reason for that?  Or for keeping the scratchy bit?
I don't use the scratchy bit, i just cut a slice off of the bottom of the sponge, the same depth and size as the space under the panching plate . Does the job a treat.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on November 16, 2018, 11:39:13 PM
Julie - that's much thicker than my original disintegrating one - any reason for that?  Or for keeping the scratchy bit?
I don't use the scratchy bit, i just cut a slice off of the bottom of the sponge, the same depth and size as the space under the panching plate . Does the job a treat.

Ahh - I thought that photo was showing how you used the whole thing!  Got it now...

Funny the things we focus on - that little piece of sponge, a 30-second job to replace, when there's so many bigger ticket items looming!
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on November 26, 2018, 10:19:37 PM
Ok, so I thought I'd remove the front wheel so I could squeeze the caliper piston out with the brake lever before dismantling.  Let's see, step one: "remove the speedometer set screw." Easy enough.  Hmm, the recess looks pretty small, what size allen wrench is that?  None of mine fit.  Wait, where's my damn glasses, that doesn't look quite right:

(Attachment Link)

Wha? Quick forum search for that set screw... oh.  So this is how it's going to be, huh? (sighs...)

I found the speedo cable set screw in the parts book... Frame Group, Block #2A, Ref. #437, Part #93700-05016-0A, "screw, oval, 5x16".  I can't find the tach cable set screw in the parts book.  I declared earlier that I had read somewhere that they're the same screw, but not sure now where I came by this info.  Can anyone confirm whether they're in fact the same screw?
Title: Re: New (to me!) '77 CB400F - US model
Post by: Nurse Julie on November 26, 2018, 10:32:52 PM
Cross reference with the CMSNL fiche

 https://www.cmsnl.com/honda-cb400f-four_model14342/
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on November 26, 2018, 11:19:13 PM
Cross reference with the CMSNL fiche

 https://www.cmsnl.com/honda-cb400f-four_model14342/

Hmm... seem to be the same diagrams I've got already - anyway, I don't see the tach cable set screw...
Title: Re: New (to me!) '77 CB400F - US model
Post by: taysidedragon on November 27, 2018, 12:24:34 AM
I'm pretty sure that they are the same size. I'll check tomorrow.

I bought a set of engine case screws online for my bike which included the tach cable screw, but it was completely wrong. I cut down a longer screw to the right length in the end.
Title: Re: New (to me!) '77 CB400F - US model
Post by: taysidedragon on November 27, 2018, 10:12:44 AM



Hmm... seem to be the same diagrams I've got already - anyway, I don't see the tach cable set screw...

I just checked mine. 5 x 18mm countersunk head and it does fit the Speedo drive as well.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on November 27, 2018, 10:42:32 AM
I just checked mine. 5 x 18mm countersunk head and it does fit the Speedo drive as well.

Thanks taysidedragon!  Sounds like a couple of mm length makes no difference in this instance...

Are there any threads which focus on mistakes or omissions in the technical information most of us seem to use?  I've been reading through earlier posts as I've had time to spare, and I occasionally come across discussions similar to this one, people looking for info about parts or discussing misinformation in the books - for example, typos or outright errors in the Haynes, Clymer or Honda workshop manuals, missing items from parts catalogs (like this screw)... it would be nice if there were a spot a newbie like me could go and make note of these issues...
Title: Re: New (to me!) '77 CB400F - US model
Post by: Nurse Julie on November 27, 2018, 10:52:44 AM
We have a section for errors

http://www.sohc.co.uk/index.php/topic,13453.msg106009.html#msg106009

Not too much in there but the usual saying is 'don't believe everything you read or see' especially if was translated from Japanese to English fifty years ago !!!
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on November 27, 2018, 11:44:11 AM
Thanks Julie!

By the way, I finally got the bike into bed for the winter - in my neighbor's garage, which is more like a large walk-out basement with big opening doors.  It's unheated, but the bike is far from the doors and no vehicles use the space, so there won't be any standing water from snow melt off a car - like there would be in my tiny garage.  I've got the fuel tank, carbs and front brake parts in my own warm basement, hopefully I'll find the time to rehabilitate them over the winter...
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on December 04, 2018, 01:58:25 PM
I'm starting a shopping list...

Based on the appearance and condition of the front brake reservoir diaphragm (http://www.sohc.co.uk/index.php/topic,17461.msg149647/topicseen.html#msg149647 (http://www.sohc.co.uk/index.php/topic,17461.msg149647/topicseen.html#msg149647)) and the piston/caliper/pads (http://www.sohc.co.uk/index.php/topic,17461.msg149803/topicseen.html#msg149803 (http://www.sohc.co.uk/index.php/topic,17461.msg149803/topicseen.html#msg149803)), should I just assume the master cylinder should be rebuilt (or replaced with a pattern one)?  Will I know if I dismantle it and examine the condition of the parts? I don't really want to spend the money if it's not necessary, but it could be full of 40-year-old parts, and it is the brakes, after all...

Same question with the carbs, too, I guess - should I dismantle them and examine the jets, etc, to determine a course of action, or does one usually just "play it safe" and have a complete rebuild kit on hand?  How will I know if a good cleaning is enough, or whether I should replace all the replaceable bits?
Title: Re: New (to me!) '77 CB400F - US model
Post by: Laverda Dave on December 05, 2018, 10:09:29 AM
I tried to repair the original front caliper on my 400/4 but it was beyond help with both the fluid union and the bleed nipple snapped in the housing. I bought a pattern caliper from DSS along with a master cylinder repair kit. The master cylinder was an easy rebuild. The hardest part is removing the internal circlip to enable piston removal. You need to buy a cheap pair of long nose or circlip pliers and maybe grind the ends down to fit. Easy job to do though and you keep the original master cylinder with the correct exterior finish, the pattern ones are painted black.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on December 05, 2018, 10:45:29 AM
I tried to repair the original front caliper on my 400/4 but it was beyond help with both the fluid union and the bleed nipple snapped in the housing. I bought a pattern caliper from DSS along with a master cylinder repair kit. The master cylinder was an easy rebuild. The hardest part is removing the internal circlip to enable piston removal. You need to buy a cheap pair of long nose or circlip pliers and maybe grind the ends down to fit. Easy job to do though and you keep the original master cylinder with the correct exterior finish, the pattern ones are painted black.

Thanks Laverda - I was planning to purchase a stainless steel piston to replace the slightly pitted/corroded caliper piston (and a new piston seal, too, of course!).  But when I initially removed the caliper, I wasn't able to loosen the fluid union or bleed nipple.  So before I buy anything, I'll see if I can remove those items without damaging anything.  Any advice for this?  I've got plenty of time for penetrating oil, etc - I could even simply drop the whole unit into something to soak, for months if need be.

I'll suppose I'll dismantle the MC as well and see how things look before I buy anything...
Title: Re: New (to me!) '77 CB400F - US model
Post by: taysidedragon on December 05, 2018, 11:18:51 AM
Try some heat on the offending parts. It may be enough to break the joint. Need to be careful with the heat on the aluminium caliper body of course.
If that fails then soak the body in a container of diesel oil or penetrating oil for a few weeks.
Good luck!
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on December 05, 2018, 11:24:42 AM
Try some heat on the offending parts. It may be enough to break the joint. Need to be careful with the heat on the aluminium caliper body of course.
If that fails then soak the body in a container of diesel oil or penetrating oil for a few weeks.
Good luck!

Thanks taysidedragon!  I'll give it a try...
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on December 05, 2018, 12:02:37 PM
Use one of the disposable cartride plumbers torches and warm the alloy round the fittings till slightly uncomfortable to touch then use a long six sided socket with a tee bar so you are turning evenly not twisting. Never failed to get one out yet. If the pipe union is really bad cut the pipe off flush with the top of the nut and follow same instructions.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on December 05, 2018, 12:06:10 PM
Use one of the disposable cartride plumbers torches and warm the alloy round the fittings till slightly uncomfortable to touch then use a long six sided socket with a tee bar so you are turning evenly not twisting. Never failed to get one out yet. If the pipe union is really bad cut the pipe off flush with the top of the nut and follow same instructions.

Cheers for the tips Bryanj - I don't have a t-bar, but who doesn't like to buy a new tool?!?
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on December 05, 2018, 09:27:55 PM
I woild say send it to me and i would do it for you but two trips accross the pond would get a bit pricey!!
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on December 06, 2018, 12:35:37 AM
I woild say send it to me and i would do it for you but two trips accross the pond would get a bit pricey!!

Yeah - anyway, I'm looking forward to working on this myself.

I must add, though - you're the second member here who has suggested they would do such a job for me if I wanted to send a part.  This is a very kind gesture, and really makes me feel like I've found a proper community of people I'd like to associate with.  So thank you, all, for that!  8)
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on December 06, 2018, 03:45:12 AM
If it does all gp wrong the caliper is the same on the 500/550 four and the 500 twin so plenty out there.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on December 06, 2018, 10:36:34 AM
If it does all gp wrong the caliper is the same on the 500/550 four and the 500 twin so plenty out there.

Noted, thanks!
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on December 06, 2018, 11:47:29 PM
I started work on the brake master cylinder.  Laverda120 says the pattern replacements are painted black, and to keep my OEM one for the original finish.  I find that the finish is a bare metal look on the top, but black around the bottom, sort of 1/2-and-1/2.  Interesting...

The brake lever bushing (that is held in place by the little plate) was like a black sticky paste, rather than rubber; I scooped it out and will replace it during the rebuild.

I could see no sign of the spring clip that holds the piston dust boot on, so I just pulled the dust boot off, in a few pieces.  It took me awhile to even find the clip afterwards, it was rusty and blended in with the rest of the junk remarkably well!  But I eventually found it and removed it; now the c-clip is next.  One end is free to move, but the other is stuck fast; I'll give it a weekend soak with penetrating oil and come back to it.  The piston moves freely, though, so I hope the cylinder/reservoir piece will clean up well...
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on December 12, 2018, 10:35:05 AM
The MC is apart - I couldn't get my clip pliers in there (not an uncommon issue, I guess); I was able to hook the "free" end of the c-clip with a pick and drag it out - bent up in the process, but it'll be replaced so no matter.  The rest came out with a punch and some gentle persuasion through the banjo bolt end.  Now I need to clean up the gunk that was gumming up the c-clip and piston retaining washer...
Title: Re: New (to me!) '77 CB400F - US model
Post by: Laverda Dave on December 12, 2018, 10:40:39 AM
Well done. Nothing beats the 'I did it feeling'.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on December 12, 2018, 10:42:40 PM
Well done. Nothing beats the 'I did it feeling'.

Thanks Laverda, you're right!  Now to sort out how to clean up the rest without damaging anything...
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on December 18, 2018, 10:25:19 AM
I found a cheap used Haynes manual.  The author, when writing about front brake maintenance, said: "Check also that there are no small stones etc, in the reservoir; its exposed position invites vandalism."

Seriously?  Is this how bike vandals strike?  Should I consider a master cylinder cap lock?  If I use one, can I get a reduction on my insurance premium?  ;)
Title: Re: New (to me!) '77 CB400F - US model
Post by: Lobo on December 18, 2018, 10:08:35 PM
Years ago when I used to visit the g/f in the nurses home I’d park the 400F under a fire escape. (Leeds / UK). Upon leaving one night I happened to notice pooling abouts the front end; some bloody low-life had semi-cut through the brake hose - my guess being that it looked in one piece and thus he hoped I wouldn’t notice until too late. Don’t underestimate the scum who seem to be everywhere...
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on December 23, 2018, 07:38:23 PM
Is this a normal arrangement for the underside of the ignition switch?  What's the story with the thin wire that's clearly cutting into the plug?  Click to zoom right in...

edit: not sure why the thumbnail is sideways, but the external view seems to be right...

[attach=1]
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on December 23, 2018, 08:14:42 PM
Switch is broken, you can see where it's been glued, my guess is that the wire is to support the wiring plug as the glue wasn't strong enough to do the job. Looks like you'll be needing a new ignition switch.

That would explain it!  Can I replace the switch while retaining the lock, so I can use the same key?  The bike came with only one key, and I just got a couple copies made.  Not to mention the seat and fuel cap locks...
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on December 23, 2018, 09:06:23 PM
Emgo do a replacement plastic switch part but get the correct one as there are two different ones.

Some people on here decry emgo but i have used their parts for many years with few failures.

You can find an Emgo catalogue on line.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on December 23, 2018, 10:09:14 PM
Emgo do a replacement plastic switch part but get the correct one as there are two different ones.

Some people on here decry emgo but i have used their parts for many years with few failures.

You can find an Emgo catalogue on line.

This is for the ignition switch?  Not sure what the "plastic part" is, the bit that looks glued onto what looks like a metal body of the switch?
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on December 23, 2018, 10:20:01 PM
Yes the complete white plastic part which clips to the metal body. If you pm me your email i will send you some pics and links
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on December 23, 2018, 10:39:07 PM
Will do, thanks!
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on December 23, 2018, 11:30:18 PM
Try this link page 69 and 70



http://www.emgo.com/images/pdf/2017Tools.pdf
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on January 06, 2019, 07:19:40 PM
Might as well keep the ignition switch discussion going here...

I removed and dismantled the switch - well, the switch self-dismantled before I got it disconnected, and small parts scattered to the floor beneath the bike.  There's two very small ball bearings and springs which stayed put, thankfully, but I definitely heard other bits jingle to the floor, so I looked carefully around and found two springs, two contact pieces, and a screw.  After close inspection, I believe the screw to be a red herring, and not part of the switch at all - just happened to be lying nearby on the floor when I started searching.  It looks very much like a screw commonly used to secure wall switch and outlet cover plates here in the US.

Switch with glue:

[attach=1]


Switch and back cover:

[attach=2]


Guts - it all seems to go back together only one way, so if I tried to reuse it, I could sort it out:

[attach=3]


Mystery screw:

[attach=4]

Interestingly, despite all the wire and glue, the plastic cover doesn't appear to be broken at all, nor does the metal housing - but the cover doesn't hold tightly when installed even without the switch guts.  But the glue is filling the slots that the tabs should be gripping (except where the tabs were in place to displace the glue while it was setting), so maybe no surprise there... I think I need to try to clear all the glue away and see what's what - actually I think it might be epoxy-like JB Weld, so I'm in for a treat...
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on January 09, 2019, 02:06:53 PM
I removed all the glue.  It wasn't too bad a job; it scraped off the metal pretty easily, and peeled off the plastic switch cover in "sheets" with just a fingernail.  I doubt it was doing much, if anything, and that the bailing wire was doing all the work - as evidenced by the fact that the electrical bits at the bottom of the switch self-destructed shortly after I cut that wire.  Anyway, I don't see any actual damage to any part.  The cover still seems a bit loose (probably why it was glued and wired in the first place!); I think I might be able to soften the tabs with heat and bend them out a bit to see if it would hold - but a whole new switch and cover plate (Emgo) is only $8 delivered, so I ordered one.  We'll see how a new one fits before I decide how to proceed...
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on January 09, 2019, 02:15:41 PM
Ok if I keep adding posts about random quick stuff here?

Speedometer and tachometer cable set screws...

Ok, so I thought I'd remove the front wheel so I could squeeze the caliper piston out with the brake lever before dismantling.  Let's see, step one: "remove the speedometer set screw." Easy enough.  Hmm, the recess looks pretty small, what size allen wrench is that?  None of mine fit.  Wait, where's my damn glasses, that doesn't look quite right:

(Attachment Link)

Wha? Quick forum search for that set screw... oh.  So this is how it's going to be, huh? (sighs...)

I found the speedo cable set screw in the parts book... Frame Group, Block #2A, Ref. #437, Part #93700-05016-0A, "screw, oval, 5x16".  I can't find the tach cable set screw in the parts book.  I declared earlier that I had read somewhere that they're the same screw, but not sure now where I came by this info.  Can anyone confirm whether they're in fact the same screw?

I removed both of those set screws... drilled out the knackered heads, tapped a Torx bit into the hole and turned both right out.  Turns out the speedo cable screw was 12mm and the tach cable screw was 16mm. The tach screw hole is blind, and the 12mm is too short.  The speedo screw mounting hole (at the front hub) is open at both ends, and while the 12mm seems to work fine, the 16mm fits and in fact comes almost flush with the back of the hole, so it's probably a better choice anyway.  I'll replace them both with 16mm screws.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on January 09, 2019, 02:21:26 PM
Regarding the clutch...

It seemed to work fine three years ago when I rode it last, but now it's become extremely difficult to pull.  I won't hazard a numerical guess about the actual force required, but it's not safe to ride in this condition.  It can be fully pulled, and it does return on its own, albeit a bit sluggishly.

Aside from the obvious possibility of a binding cable, what else could be the trouble?

Might this be expected of a bike that's been sitting for a couple of years?  In other words, should I be thinking about solving this problem before I try running it (whenever that turns out to be)?  Or might it sort itself out with some oil circulation and exercise?
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on January 09, 2019, 02:37:29 PM
Almost certainly cable and as a hint DO NOT oil an original cable as the onner is rubber coated and the outer nylon lined, oil tends to "swell" both and make the cable tight. Aftermarket cables may dispense with one or both of the linings and be safe to oil but i dont comment on that!!
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on January 09, 2019, 03:55:10 PM
Almost certainly cable and as a hint DO NOT oil an original cable as the onner is rubber coated and the outer nylon lined, oil tends to "swell" both and make the cable tight. Aftermarket cables may dispense with one or both of the linings and be safe to oil but i dont comment on that!!

Thanks for all you helpful advice bryanj!
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on January 20, 2019, 07:29:49 PM
I took a look at the fuel tank today.  The interior looks to be pretty rust-free, but I can't see in very far... and I hear some fine particles rolling around inside when I twirl the tank about.

I removed the petcock and the fuel filter tube stayed in the tank, the gasket sealing it to the petcock was a bit chowdered.  I made it worse pulling it out of the petcock nut.  I was able to drag the filter out, revealing rust in the petcock mounting "tube."  Still can't see inside the tank, though, to try to get a sense of what's going on in there.  Pics below - the fine rusty-dusty particles fell from the filter when I tapped it on the table...

[attach=1]

[attach=2]


I don't know if the petcock innards are in working condition... body is riveted, is there any hope of refurbishing this one, or should I just spring for a new one?
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on January 20, 2019, 09:13:55 PM
What size is the tread on the tank, if 18mm i can help you.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on January 20, 2019, 09:21:24 PM
What size is the tread on the tank, if 18mm i can help you.

Not sure... just measure across the outlet exterior?  I do know that the nut holding it on takes a 19mm wrench.

Help in what way?  We are on different continents... aren't we?
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on January 20, 2019, 09:54:42 PM
Measure the diameter of the spigot, i have a pattern, new, 18mm petcock complete with strainer and seals, if it fits you can have it for post cost.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on January 20, 2019, 10:14:45 PM
Measure the diameter of the spigot, i have a pattern, new, 18mm petcock complete with strainer and seals, if it fits you can have it for post cost.

I think the '77 bikes have a different petcock than the earlier models... anyway, I measured across the threaded fuel tank outlet (see second pic a few posts back) - its outer diameter is 13.95mm, inner diameter 8.72mm... does this help?
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on January 21, 2019, 12:16:11 AM
Sorry that means the one i have wont fit mate, try looking for 14mm petcock on fleabay.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on January 21, 2019, 03:07:31 AM
Sorry that means the one i have wont fit mate, try looking for 14mm petcock on fleabay.

Thanks anyway!

Is my one no good, then?  The filter tube can't be reinstalled and the gasket renewed?
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on January 21, 2019, 09:31:21 AM
If you can get them yes but frequently nowadays you can only find the complete petcock.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on January 21, 2019, 05:46:03 PM
David Silver's US site sells just the strainer and o-ring, as well as the whole petcock:

https://www.davidsilverspares.com/CB400F-SUPER-SPORT-1977-USA/part_163258/ (https://www.davidsilverspares.com/CB400F-SUPER-SPORT-1977-USA/part_163258/)

Interestingly, though, his UK site only lists the complete unit.

Does anyone know how this thing is supposed to install?  Does the strainer just insert flush into the tank opening, then the o-ring drops into the petcock fitting and you just tighten it up?  That's how I found mine, except the o-ring was wedged beneath the big retaining nut.  Could be it just forced its way in there over time?

EDIT: DSS lists two different "genuine" parts at two different prices.  Huh.  One of them has a good photo showing the inside of the retaining nut:

(https://www.davidsilverspares.com/graphics/parts/16951377703_3_large.jpg)

I'm guessing that o-ring isn't meant to retain that strainer, if it was it would probably restrict flow to the reserve opening.  But it does look a bit like the strainer is meant to stay attached to the petcock, which mine clearly didn't...

Or, do you drop the strainer over the tube, then slide the o-ring over the strainer, so that the open end of the strainer is held captive by the o-ring down inside the retaining nut?

EDIT x2: That pic doesn't show the strainer... so I'm still not sure how it's supposed to go...
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on January 21, 2019, 06:25:06 PM
Just recently done a cbx 550 so i can definitively tell you that if you do not want a leak the strainer pushes into the petcock then you fit the washer/O ring before fitting the assembly to the tank
Title: Re: New (to me!) '77 CB400F - US model
Post by: Nurse Julie on January 21, 2019, 07:05:40 PM
Yep, same as the 400/4 then Bryan.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on January 21, 2019, 09:01:55 PM
I'm sorry guys, but I'm just not clear on how this thing is supposed to be configured.

When I removed the petcock, the o-ring was stuck beneath the threads of the retaining nut, and the strainer remained tightly stuck in the tank opening, perfectly flush with it.  It was a tight fit between the little collar on the open end (which is how the gasket is supposed to hold it in place?) and the tank outlet.

[attach=1]


I needed a sharp 90º pick tool to reach in and hook it and drag it out.  As far as I know, the petcock was working and not leaking, but it sounds like that is not the correct arrangement?

Now this photo shows the how the strainer lies in relation to the reserve opening when the petcock is on its side; it fits loosely enough on the inner tube that it doesn't block the reserve opening:

[attach=2]


But if the gasket is properly round with an opening right in the middle, holding the strainer down against the petcock body, I would expect the strainer to remain centered, with the collar blocking the reserve opening:

[attach=3]


But this is the correct arrangement?

Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on January 21, 2019, 10:02:19 PM
Yup, reserve fuel still goes through the srainer on normal through the tubeso seal position means nothing.
As to the tube staying in the tank and being flush---they all do that sir just sorta happens.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on February 04, 2019, 09:46:02 PM
Just recently done a cbx 550 so i can definitively tell you that if you do not want a leak the strainer pushes into the petcock then you fit the washer/O ring before fitting the assembly to the tank

Yup, reserve fuel still goes through the srainer on normal through the tubeso seal position means nothing.
As to the tube staying in the tank and being flush---they all do that sir just sorta happens.

(https://advrider.com/f/styles/advrider_smilies/hmmm.gif)

I can't get my head around this apparent contradiction - the o-ring must go on over the strainer if you don't want leaks, but then the strainer doesn't stay there, but ends up "outside" the o-ring, flush in the tank - and they all do that?  Shouldn't they all leak, then?
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on February 04, 2019, 10:03:54 PM
Regarding the clutch...

It seemed to work fine three years ago when I rode it last, but now it's become extremely difficult to pull.  I won't hazard a numerical guess about the actual force required, but it's not safe to ride in this condition.  It can be fully pulled, and it does return on its own, albeit a bit sluggishly.

Aside from the obvious possibility of a binding cable, what else could be the trouble?

Might this be expected of a bike that's been sitting for a couple of years?  In other words, should I be thinking about solving this problem before I try running it (whenever that turns out to be)?  Or might it sort itself out with some oil circulation and exercise?

Almost certainly cable and as a hint DO NOT oil an original cable as the onner is rubber coated and the outer nylon lined, oil tends to "swell" both and make the cable tight. Aftermarket cables may dispense with one or both of the linings and be safe to oil but i dont comment on that!!

Bryan - after our discussion on the other forum about clutch cable sources, I went looking and found a couple, but while they show photos of cables correctly tagged with part numbers, I can't get them to confirm that they're actually correct - one ebay guy just promised that what I see is what I get (despite a reviewer claiming he didn't get what was pictured when he ordered).  Partsnmore in Canada has never heard of a high-bar version of the bike, so can't comment, but asked for measurements.  So, I went to the bike today to remove the clutch cable...

Recall your comment above about the cable.  Now take a look at the photos:

I barely got one of the clutch cover screws off - rusty!

[attach=1]


This doesn't look great:

[attach=2]


Water must have gotten in through the cable opening?

[attach=3]


I was able to exercise the clutch with great difficulty, and it returned to rest, but now that the cable is out, I cannot budge the wire in its housing!

[attach=4]


Yep, new cable (and cover plate screw) time!  Any way to prevent that moisture intrusion?
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on February 04, 2019, 10:28:56 PM
Looking at the clutch cable will the nipple on the end go through the hole in the screwed adjuster? Also give me length of outer cable and inner cable.
Yes water gets in through the adjuster but that cover is supposed to come off at service to check clutch adjustment and most mechs of my era  used to lube everything excessively!!
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on February 04, 2019, 10:57:21 PM
The filter fits inside the tank spigot, it's flared at the bottom end so it can't disappear inside the tank, it's a tight fit inside the spigot so no petrol can get to the fuel tap without going through the filter, the O-Ring just seals the inner collar on the tap against the bottom of the tank spigot, the large outer nut compresses it against the spigot so it seals and stops any leaking petrol. Most people tend to overtighten the outer nut which causes the O-Ring to expand, flatten out and get stuck in the threads of the outer nut.  Hence why yours looks in pretty poor shape. Don't worry about the filter fitting inside the tap, so long as it fits inside the tank spigot it's doing it's job.

Oddjob, that's certainly the way I found mine, but others are suggesting other possibilities.  One thing I think I may not have considered, is that I think the '77 USA models have a different petcock than the earlier ones, so we may have been comparing apples and oranges...
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on February 04, 2019, 11:05:38 PM
Looking at the clutch cable will the nipple on the end go through the hole in the screwed adjuster? Also give me length of outer cable and inner cable.

Bryan, it's hard to tell since I can't budge the cable, but after measuring it does appear that the clutch housing end nipple would fit into the threaded adjuster if I could pull it - the nipple measures about 5.7mm at its widest, and the inner diameter of the adjuster seems to be about 6.3mm, although it's hard to measure with the cable in the way.

Dimensions...
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on February 05, 2019, 09:02:20 AM
I will have a look at my box of assorted cables and let you know. As your cable is fubared i would clamp the end of the outer by yhe adjuster in a vice and use a spanner to turn the adjuster away from it with lost of WD
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on February 05, 2019, 11:43:41 AM
Looking at the clutch cable will the nipple on the end go through the hole in the screwed adjuster?

I will have a look at my box of assorted cables and let you know. As your cable is fubared i would clamp the end of the outer by yhe adjuster in a vice and use a spanner to turn the adjuster away from it with lost of WD

I wasn't quite sure of the significance of your question, but I had a look at some parts diagrams and now I think I just learned something new - the adjuster isn't part of the cable, is it?  I just thought it was all one piece, since I hadn't seen any detailed images of them separated, and mine are fused together.

I think I can find a cable here, as long as I am willing to take a chance on a seller who doesn't really know what they're selling and relying on photos to inform buyers...

I'll separate the pieces, I'll have to do it anyway.  Only problem I foresee is that the adjuster's socket where the cable housing seats could be rusted, and difficult to clean well.  That's another part that's hard to find, I've only found one so far - new stainless steel from Yamiya750.com.  Maybe if it's not too bad I can get someone to blast it clean...

EDIT: I was searching for the wrong part number for the adjuster - there's a few around, but I haven't yet found any in the US, and nothing on ebay...
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on February 05, 2019, 04:54:45 PM
Dimensions...
  • Inner cable length, ball-end to ball-end… 45 inches
  • Outer housing length, metal sleeve at handlebar to end of adjustment screw at clutch housing… 41-5/8 inches
  • Adjustment screw at clutch housing… 1-11/16 inches
  • There’s also a protective sleeve around the outer housing, about 13-1/2 inches long, which starts about 17-1/2 inches from the metal sleeve of the outer housing at the handlebar

So the highlighted dimension is not correct - I measured the outer housing without the adjuster, it's 40-1/4 inches...

 :-[
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on February 05, 2019, 04:56:25 PM
As you need to keep the adjuster and the cable is scrap a measure of mechanical violence is OK
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on February 05, 2019, 05:00:30 PM
As you need to keep the adjuster and the cable is scrap a measure of mechanical violence is OK

 ;D

Not too much violence needed, cable housing in a vice as you said, and the adjuster "wrenched" right off.  I cleaned it off with a wire brush and I'm soaking it in white vinegar for a day or so to see if it helps it - a small test before I try it inside the fuel tank?
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on February 05, 2019, 08:47:48 PM
I have a cable that is longer than those measurements but approx the same "free play" you can have it for postage but that is probably more than a local e bay purchase!
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on February 05, 2019, 09:05:55 PM
Thank you Bryan - I don't know how much the shipping would be, but the ebay guy I mentioned earlier has been very helpful with trying to sort out if it's really the right cable, and he's charging US$20 including shipping, so based on all that I'll probably go that way...
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on February 05, 2019, 09:23:32 PM
No problem, one of the hazards of living opposite sides of the pond!!
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on February 10, 2019, 12:09:50 AM
So I soaked the clutch adjustment bolt in white distilled vinegar for a few days, along with some fine filing, and it came up pretty neat and clean.  I'll reuse it, with plenty of lubrication/rust prevention.

The clutch lever's pivoted cable mount end is pretty badly rusted where the cable attaches.  I'd like to try to reuse it; can I safely soak it in vinegar as well?  Not sure what kind of finish it has, and whether it will handle it...

(http://www.sohc.co.uk/index.php?action=dlattach;topic=17461.0;attach=39923;image)

Also, where the lever attaches to... umm... whatever it attaches to with that nut (clutch adjusting bolt?)... the lever seemed sort of loose and a bit "floppy?" even though the nut was tight.  Is that normal?
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on February 10, 2019, 08:36:30 AM
There is, or rather should be, some "free play" in the lever movement before the mechanism starts to operate the clutch.
Title: Re: New (to me!) '77 CB400F - US model
Post by: Nurse Julie on February 10, 2019, 09:10:53 AM
These is, or should be, a little anti rattle tube on the lever fitting as well. When these are shot or missing it makes the lever feel even looser.
Edit...him indoors has told me I'm loosing the plot, the anti rattle is on the brake lever...doh  :-\
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on February 10, 2019, 10:17:46 AM
There is, or rather should be, some "free play" in the lever movement before the mechanism starts to operate the clutch.

I hesitated to refer to the looseness I described as "free play", because the movement I encountered wasn't just in the expected direction of travel.  The cable mount end could be gripped and pulled and pushed in and out a bit - laterally, 90º to the normal "rotational" direction of travel.  I could also hold the other end with two fingers, directly over the mounting nut, and pivot (not rotate) it slightly - basically the same movement just described, but in any direction.  Almost as if the adjustment spindle it was fastened to was made of a stiff rubber material, rather than solid metal?  Yet the locking nut was very tightly fastened... it's difficult for me to describe.  A short video would reveal all, but I'm away from the bike this week.

Would that rubber oil seal behind lever arm allow for such movement?

Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on February 10, 2019, 10:29:36 AM
These is, or should be, a little anti rattle tube on the lever fitting as well. When these are shot or missing it makes the lever feel even looser.
Edit...him indoors has told me I'm loosing the plot, the anti rattle is on the brake lever...doh  :-\

My parts book calls it simply a "bush" - mine was in place, but in many tiny pieces.  What a pricey little headache!  I bought a replacement for $3.00 (about as cheap as I could find it), as part of an order for a few more items.  If I knew the proper size and composition, I probably could nip down to my local hardware store and find something that would work fine for $3 a meter instead of $3 a centimeter, but that's the way it goes...
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on February 11, 2019, 01:07:38 AM
The clutch lever's pivoted cable mount end is pretty badly rusted where the cable attaches.  I'd like to try to reuse it; can I safely soak it in vinegar as well?  Not sure what kind of finish it has, and whether it will handle it...

Answered my own question...

before, pretty greenish finish:

[attach=1]


after soaking the lower half in vinegar:

[attach=2]

pretty greenish finish is gone (note the "vinegar-line") and there's a similar greenish rainbow sheen on the surface of the vinegar I'm soaking in.  Hopefully I can just clean it and lube it and it will stay happy...
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on February 13, 2019, 06:45:35 PM
Thank you Bryan - I don't know how much the shipping would be, but the ebay guy I mentioned earlier has been very helpful with trying to sort out if it's really the right cable, and he's charging US$20 including shipping, so based on all that I'll probably go that way...

Got the new clutch cable - it's identical in every dimension to the frozen one that came off, so that's a win!  Full marks to the seller who didn't know what he had, but went out of his way to post photos and take measurements to help me decide...

Does this thread belong on the "projects" board?  Does it make sense to keep adding to it here?
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on March 01, 2019, 06:00:11 PM
I'm ordering up some brake parts... any way to tell whether my current brake hoses are original?  Should I look for any markings in particular - or lack thereof?  End-to-end, the lower hose is 14", and the upper one is 13-1/2" ('77 US-spec with higher bars).

I'm inclined to re-use them.  They look ok - not what I'd call new, but no cracks or splits or odd bulges anywhere...
Title: Re: New (to me!) '77 CB400F - US model
Post by: hairygit on March 01, 2019, 06:43:56 PM
Personally I would not use old hoses, you have no idea how old they are, they could be breaking up internally, and let's face it, replacements are relatively cheap, especially compared to wrecking your bike in the event of a sudden hose failure!

Sent from my X6pro using Tapatalk

Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on March 01, 2019, 09:22:56 PM
Personally I would not use old hoses, you have no idea how old they are, they could be breaking up internally, and let's face it, replacements are relatively cheap, especially compared to wrecking your bike in the event of a sudden hose failure!

Here's where I'm at right now: how many parts do I replace and repairs do I make just to get the bike to the point where I can see if it works?  I want to figure out my baseline before I start dumping money into this project.

That said, however, I'm leaning toward the wisdom of your suggestion - safety should come first!  If the brake hoses were to fail when I needed them, I daresay that damaging the bike wouldn't be my top concern...
Title: Re: New (to me!) '77 CB400F - US model
Post by: Nurse Julie on March 01, 2019, 09:44:41 PM
It can be a difficult decision knowing how far to go and how much money to spend on an old bike. Safety is paramount, looks and performance are at the bottom of the list. Do enough to get it starting, running and stopping. Anything else can be done later, if you decide its worth continuing with the project.
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on March 01, 2019, 10:12:28 PM
If there are no leaks, bulges or cracks in the outer casings of the hoses, especially at the crimp ring on the fittings, the UK safety testers manual says they are good to use and if ok by those standards i would build with what you have and possibly change later.
By the same token i will not accept ANY pitting on the caliper piston and unless i had myself fitted a new seal recently would not reuse a seal.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on March 08, 2019, 12:46:43 AM
The discussion about the cam chain adjuster in the 350-400 section has me wondering - I don't really understand exactly how this thing works, and I haven't run the engine yet.  is there any way to check how well the adjuster is working, if at all, without the engine running?

The shop manual just says to loosen the lock nut and tension adjusting bolt, then re-tighten both (engine running).  How much re-tightening torque are we talking about here?
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on March 08, 2019, 06:01:12 AM
you can replace the tensioner by just removing the lower crankcase but its still an engine out job. remind me what miles your bike has on it? If you have been reading about them you now know what goes wrong with the tensioner when chain gets slack, they don't work very well as the springs loose strength but you can use the small screwdriver down the blanked off hole to see if it is moving at all.
If it was running before it will again before deciding what to do and you will not loose anything except a small amount of your time, it can always be done later just do not get disheartened.
Title: Re: New (to me!) '77 CB400F - US model
Post by: Nurse Julie on March 08, 2019, 08:53:27 AM
   How much re-tightening torque are we talking about here?
There is no torque, its automatic spring tension that enables the process of adjusting the chain. You only undo the lock nut and adjuster bolt to allow free movement of the chain tensioner adjuster bar to allow the springs to push the chain tensioner adjuster bar to be pushed down further on to the horse shoe, which in turn, pushes the tensioner slipper on to the chain to take up the slack. It's an automatic tensioner. But for the process to work and remove any cam chain rattle from a slack chain, the chain must still be within service limit, the horse shoe pivot not seized and the spring not weak. As Bryan says, worry not now, sort it out at a later date if needed.
Title: Re: New (to me!) '77 CB400F - US model
Post by: K2-K6 on March 08, 2019, 09:18:28 AM
It maybe worth a look into Julie's engine rebuild thread to fully view the component parts and give yourself a broader picture in overview.

If you want to check if tensioner is moving on a non running engine, loosen the set/pinch bolt,  put something like a small screwdriver against the spring rod, and get someone to turn the crank anticlockwise (looking at ignition side) slowly.
This'll put the camchain into tension on the "wrong" side and should push the rod towards your hand if the pivot etc are free.

If it moves,  then turn the crank clockwise and it should go back away from you again. At this point you can lock the pinch bolt again as all the camchain slack will be placed next to the tensioner and should be adjusted and held by the tensioner.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on March 08, 2019, 05:09:05 PM
Thanks guys...

you can replace the tensioner by just removing the lower crankcase but its still an engine out job. remind me what miles your bike has on it? If you have been reading about them you now know what goes wrong with the tensioner when chain gets slack, they don't work very well as the springs loose strength but you can use the small screwdriver down the blanked off hole to see if it is moving at all.
If it was running before it will again before deciding what to do and you will not loose anything except a small amount of your time, it can always be done later just do not get disheartened.

Still just doing my research - not disheartened yet!  The bike currently has 22K miles; three years ago when I rode it, it had 21.7K miles - so not much has changed in that time.  On that ride, I recorded a video to try to capture engine noise - not because I suspected anything wrong, but just because I had no idea what sounds are "normal" for this engine.  I posted this link waaaaaaay back in post #1 of this thread; here it is again FYI:

https://youtu.be/Szxke8bD_dg (https://youtu.be/Szxke8bD_dg)

I can say that while deep maintenance history is unknown, recent maintenance history appears to have been lacking...

   How much re-tightening torque are we talking about here?
There is no torque, its automatic spring tension that enables the process of adjusting the chain. You only undo the lock nut and adjuster bolt to allow free movement of the chain tensioner adjuster bar to allow the springs to push the chain tensioner adjuster bar to be pushed down further on to the horse shoe, which in turn, pushes the tensioner slipper on to the chain to take up the slack. It's an automatic tensioner. But for the process to work and remove any cam chain rattle from a slack chain, the chain must still be within service limit, the horse shoe pivot not seized and the spring not weak. As Bryan says, worry not now, sort it out at a later date if needed.

We may be talking semantics here.  Since there is a locking nut, I figured that the adjuster wasn't relying on torque alone to hold it in place, but the manual does say to re-tighten it, and to my mind that means some kind of torque - even if the intent is only to tighten it just until resistance is felt.  The answer to "how tight should it be?" is a torque value, isn't it?  The manual reveals nothing on this score...

It maybe worth a look into Julie's engine rebuild thread to fully view the component parts and give yourself a broader picture in overview.

If you want to check if tensioner is moving on a non running engine, loosen the set/pinch bolt,  put something like a small screwdriver against the spring rod, and get someone to turn the crank anticlockwise (looking at ignition side) slowly.
This'll put the camchain into tension on the "wrong" side and should push the rod towards your hand if the pivot etc are free.

If it moves,  then turn the crank clockwise and it should go back away from you again. At this point you can lock the pinch bolt again as all the camchain slack will be placed next to the tensioner and should be adjusted and held by the tensioner.

I'll look again - I read her thread "cover to cover," but it was almost at a single sitting; like binge-watching your favorite TV series, retention sometimes suffers.  Is your "screwdriver against the spring rod" the same as Bryanj's "screwdriver down the blanked off hole"?
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on March 08, 2019, 05:18:34 PM
Yup it is, 22k if look after and adjusted regularly should be OK, ignored, abused and not adjusted often wrecked------who knows!
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on March 08, 2019, 05:31:10 PM
Yup it is, 22k if look after and adjusted regularly should be OK, ignored, abused and not adjusted often wrecked------who knows!

We'll all know... hopefully sooner rather than later!  But right now I've got six-foot snow drifts in my driveway and it was 5℉ (-15C) this morning when I left my house for work...
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on March 08, 2019, 06:07:51 PM
Only answer to that is stay in and put more logs on the fire!!
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on March 08, 2019, 08:59:48 PM
Only answer to that is stay in and put more logs on the fire!!

True!  Alas, I can't work at my job from home...
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on March 10, 2019, 04:00:35 PM
How much re-tightening torque are we talking about here?
There is no torque, its automatic spring tension that enables the process of adjusting the chain. You only undo the lock nut and adjuster bolt to allow free movement of the chain tensioner adjuster bar to allow the springs to push the chain tensioner adjuster bar to be pushed down further on to the horse shoe, which in turn, pushes the tensioner slipper on to the chain to take up the slack. It's an automatic tensioner. But for the process to work and remove any cam chain rattle from a slack chain, the chain must still be within service limit, the horse shoe pivot not seized and the spring not weak. As Bryan says, worry not now, sort it out at a later date if needed.

We may be talking semantics here.  Since there is a locking nut, I figured that the adjuster wasn't relying on torque alone to hold it in place, but the manual does say to re-tighten it, and to my mind that means some kind of torque - even if the intent is only to tighten it just until resistance is felt.  The answer to "how tight should it be?" is a torque value, isn't it?  The manual reveals nothing on this score...

From Haynes - "Turn it again inwards, until slight resistance is felt, then re-tighten the locknut."
Title: Re: New (to me!) '77 CB400F - US model
Post by: Nurse Julie on March 10, 2019, 04:18:16 PM
How much re-tightening torque are we talking about here?
There is no torque, its automatic spring tension that enables the process of adjusting the chain. You only undo the lock nut and adjuster bolt to allow free movement of the chain tensioner adjuster bar to allow the springs to push the chain tensioner adjuster bar to be pushed down further on to the horse shoe, which in turn, pushes the tensioner slipper on to the chain to take up the slack. It's an automatic tensioner. But for the process to work and remove any cam chain rattle from a slack chain, the chain must still be within service limit, the horse shoe pivot not seized and the spring not weak. As Bryan says, worry not now, sort it out at a later date if needed.

We may be talking semantics here.  Since there is a locking nut, I figured that the adjuster wasn't relying on torque alone to hold it in place, but the manual does say to re-tighten it, and to my mind that means some kind of torque - even if the intent is only to tighten it just until resistance is felt.  The answer to "how tight should it be?" is a torque value, isn't it?  The manual reveals nothing on this score...

From Haynes - "Turn it again inwards, until slight resistance is felt, then re-tighten the locknut."
Yes, after you have released the lock nut and washer and the chain has self tensioned. You do not tighten the bolt and lick nut to achieve tension, you loosen it, which achieves tension via the springs.The tension they are talking about is the bolt on the arm.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on March 10, 2019, 04:20:34 PM
Yes, after you have released the lick nut and washer and the chain has self tensioned. You do not tighten the bolt and lick nut to achieve tension, you loosen it, which achieves tension via the springs.

Understood - it was the very non-specific "re-tighten" instruction in the manual that had me wondering, is all...
Title: Re: New (to me!) '77 CB400F - US model
Post by: Nurse Julie on March 10, 2019, 04:23:57 PM
Yes, after you have released the lick nut and washer and the chain has self tensioned. You do not tighten the bolt and lick nut to achieve tension, you loosen it, which achieves tension via the springs.

Understood - it was the very non-specific "re-tighten" instruction in the manual that had me wondering, is all...
It doesn't need to be any more specific really, you are only doing up what you undone previously, if you get my drift.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on March 30, 2019, 11:13:47 AM
I can't be certain, but I think I may hold the record here for keeping the longest thread running without actually doing anything.  Just saying...  :-[  ::)

I do wish I had the bike in my own garage, it sure would make it easier to sort through some of these things...

I'm wondering about whether the bike was dropped, or had some sort of accident, based on the condition (three years ago) of the shift lever (bent), the left rear turn signal (bent), and the rear fender (broken). 

When I first saw the bike three years ago, it looked like this:

(https://lh3.googleusercontent.com/doMZhMk-KB-5WJcFiay6SoX3IRY-BnEKWx0mLUtMiGFCuL_Tu0AA7xFYMp_gTTDc97s4SazWe5_C3s0cQfObCHOZzgCuGLrjizedINmYAphOZtho-aVxWgske5lri8RYS7QJaCuiEs9656Nz8JHbsWdnPOikjuTs29pU_NpcGD8iogoXKbdq4xRCBkrj5Bn26L-pGwA5eUpfVyy9oUT4Ai9VyLxVSIJnH78gx2z0UdnatmdXZdlSzmu1ce4VwNEsKd8nJvNYvF1aG3S8UOJw2kOkgLZg8lIMxf6IJBg78td2FTt5NHAE3L6C00IUevvIN0W2lwmyen02HS3yQuD-Oqw87h1s44LSV0orPgqKRRDmBugp6juHFvDrdEWj6Gp6yw4JinC04W62ud3WHsZ_3rR0znedD9FkrIBo7GPpoG8R9NQo8lMspcMKsDGLcjoYf0lBKh97rZEBI1FzXtC2mLWeMg0etmcWANSWNregI0X09ylPCPeV6beiKkW9EGeiXhrNLWRFIe0Gk1pFgBpbPpRgIOZQd8DIbFuGCJe5oumz9XiNjMUwhyNmgaP_gpA8OYI9Y4yCxVA4w-V1LmXljaRhTC9kp9kMlHmRUYID7njHRDcIsy0EGmvPsLGPljTKmFTlOWIS8EFWl3mYWwyuQHQgrxdmBwWT1ZjSqLuRKiUH_jf4EwrTijjMKZy5gmOqvrvW-n8bI2Te71ao6_1VkQBo=w1576-h1182-no)

(https://lh3.googleusercontent.com/8C2lFieDQiN8IcEPN_4mPd-YNDxKet4ZkQPDaPfgQqvKPnQeqnSkTCygEN-dl7A7G9kFCdu6t-bVoGmgBp6JojPLoy6mGtrt01uZmfqpkIaXGaT4Auz-mHS8OyWB8dxdqb5q8VavEBPc4pR2h1Kum2FvhXd3Ljq5mLiENGquhZfYI00VPrXkqCEBFsLJhH1kKjluWmQr6w6qEnRIAkQD65j3tusO2Gd-Sre5t6Favpv_Jb24BSMf9D8Cs1OxQeOHaSKsoyTpmF_D6mCY0yIDat5pT1lfJw5woBqyOhe-2zGjfo-FP9gpwFrz_OMqxTJwOv166PrKxS65KUU94j0ViYpuJwrP7Z2hU625ZiDFi1FdCuD52W5R_Alga52Qu-imjXEcNYrdmVZwuDqJ01BpgnOVEqPON5aCJ73f4qYa7jv5JAiBIFcGWQ6XSDTfO6UpN0m2xg_G2xhPC-7KWkw4Tu71-lQoNObhqXHl2QCKBFW_IeDKa1hixY6HzIXKUYl9eZMNkvrqGG2vkIhu4t_8iJoARgmPuaGuVDWUUuUOtfmW9sxbZ5oHVL17RbmKiTNVvVZm-qLQooc_Xerf-se1txPOo1LDBFYSdkByT26ifNi1sdn9VloVb_FWIAIVi9LrAACs35mBAyzTuAV13xkTHfZCdZVui3i_qipT3ObhPfVJsycCG4VjekxcQPRxybxDrCzHzVYPqiuU53nrJxZljlXk=w596-h1182-no)

And the fender looked like this when it arrived, with the tail light's upper right-side mounting point broken, but that's obviously not recent, either (the rest of these pics can be zoomed in by clicking):

[attach=1]

[attach=2]

That underside mounting plate is broken in two, and some of the spot welds have parted as well, so the closer portion is free to turn when you try to remove the tail light.

I can't remember if that left rear signal was bent but secure, or just loose - either way, when I got the bike, the signal was more or less straight.  When I removed it, I found an extra (locking!) washer in the stack of mounting hardware, which was cranked so tight I thought for sure I was going to break something trying to loosen it.  The fender damage seems like it could be from vibration, although I haven't heard of this problem on these bikes, or maybe the light fixture could have been struck to cause the break.  The bent shift lever speaks for itself - but there is no other sign of impact damage, and these parts show no other scuffs or scrapes which you'd expect to see.

Turn Signal:

Here's a photo I just took of the signal brackets.  You can guess which one is the left one!

[attach=3]

I'm hopeful that I can bend it back to "normal" and go back to the correct mounting hardware and it will be right - and that the frame at the mounting point isn't bent as well.  But in the photo you can see that even the right side bracket has a bit of a curve - did that get bent over time, or is it supposed to be that way, anybody know?

Fender:

I had to get a bit rough with the broken mounting plate, as it turned with the mounting bolt and had clear intentions of shearing the wiring.  I'm not even sure where all the broken pieces of the fender are:

[attach=4]

[attach=5]

I'm keeping an eye out for a used replacement in reasonable condition - I just don't want to spend top dollar on a brand new one, which will look out of place with the rest of the bike's patina.  I've heard, I think, that a 350 fender would fit, too - there seem to be more of them on ebay, but they all have four tail light mounting points, while the 400's all seem to have three mounting points.  Some I'm seeing for sale include the tail light, so that could work - or I could just drill a hole.

If I can't find a replacement, I may just knock out a new mounting plate, wide enough for a couple of extra bolts to hold the tail light to the fender - four in line instead of just the two at the top of the tail light bracket...
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on April 03, 2019, 03:10:26 PM
No takers on the turn signal brackets?
Title: Re: New (to me!) '77 CB400F - US model
Post by: K2-K6 on April 03, 2019, 03:32:24 PM
It looks consistent with just falling over onto the floor while stationary to me. If the gear lever is not ground away underside of tip,  it would verify this. Perhaps fallen off its side stand.

Signal brackets,  I'd bend them back again either by supporting with something like a socket on the back/frame side of the bracket and tapping the face with a hammer to bring them back to flat.

If the frame ends have also twisted,  you can use an adjustable spanner on them to gently twist back to vertical to maintain alignment once the signals are mounted.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on April 03, 2019, 05:05:15 PM
It looks consistent with just falling over onto the floor while stationary to me. If the gear lever is not ground away underside of tip,  it would verify this. Perhaps fallen off its side stand.

Signal brackets,  I'd bend them back again either by supporting with something like a socket on the back/frame side of the bracket and tapping the face with a hammer to bring them back to flat.

If the frame ends have also twisted,  you can use an adjustable spanner on them to gently twist back to vertical to maintain alignment once the signals are mounted.

Thanks K2-K6 - based on my brief investigations thus far, I'm thinking that "tapping" might be underselling somewhat the effort that will be needed... but I'm at work this week, where there's access to a decent vice and lots of tools, including a wide variety of hammers...

Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on June 25, 2019, 12:59:44 PM
How much play should the side stand have?  Mine seems loose, whether its up or deployed.  A very short video:

https://youtu.be/2w5YY23Uh40 (https://youtu.be/2w5YY23Uh40)

I take it we can't embed youtube videos here?
Title: Re: New (to me!) '77 CB400F - US model
Post by: kent400 on June 25, 2019, 05:59:03 PM
Well that side stand is too loose wrong bolt maybe securing it to the frame
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on June 25, 2019, 08:53:08 PM
Well that side stand is too loose wrong bolt maybe securing it to the frame

Cool!  Another thing to add to the list!  ;D

Easy enough to check that, anyway... thanks!!
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on July 19, 2019, 02:20:04 PM
I'm reading some recent posts about cam chain tension and other engine specifics.  Waaaaay back at the distant beginning of this thread, I posted an "engine run" video - it didn't garner any attention, which I'll assume is a good thing!

Anyone want to check it out again, with an ear towards whether there's anything that sounds amiss?  Any red-flag rumbles or rattles or what have you?  I know, a crappy video is a difficult diagnostic tool...

https://youtu.be/Szxke8bD_dg (https://youtu.be/Szxke8bD_dg)

Although I made that video almost exactly four years ago, the previous owner only put about 300 further miles on the bike before I got it, so it's likely still representative of the engine condition...
Title: Re: New (to me!) '77 CB400F - US model
Post by: Nurse Julie on July 19, 2019, 02:47:51 PM
Impossible to tell anything with it idling far too high. But, like you say, videos are difficult to hear anything on. It sounds like there is a rattle there somewhere, which would not be expected with the revs that high. Also, running quite poorly by the sounds of it, sounds like it needs a good service and basic maintenance before any real diagnostics can take place.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on July 19, 2019, 03:13:03 PM
Impossible to tell anything with it idling far too high. But, like you say, videos are difficult to hear anything on. It sounds like there is a rattle there somewhere, which would not be expected with the revs that high. Also, running quite poorly by the sounds of it, sounds like it needs a good service and basic maintenance before any real diagnostics can take place.

Yes - it was running very poorly at that time - and probably would be now, too... ;D
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on July 19, 2019, 08:35:26 PM
Well that side stand is too loose wrong bolt maybe securing it to the frame

Not sure if it's the wrong bolt, but I don't think so.  The non-threaded portion of the bolt is an ever-so-slightly loose fit in the frame bracket - I think the problem is that the stand is bent.  Observe how the outside tang splays out at the top, and the resulting gap where the bolt's head doesn't touch as a result:

[attach=1]

Evidence is stacking up that this thing was dropped on the left side, or in some kind of accident.  The bent side-stand (although I would think the "inside" tang would be bent if the stand got pushed inwards somehow), and also the gear lever...

[attach=2]

... and the rear turn signal, of course...

[attach=3]

Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on July 19, 2019, 10:31:27 PM
The "Opening Up" of the slot is a fairly common thing to see but with that and wear on the frame lug you get too much "slop" I have before now carefully straightened the stand for and put a shim washer under the bolt head to keep it tighter.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on July 19, 2019, 11:13:22 PM
The "Opening Up" of the slot is a fairly common thing to see but with that and wear on the frame lug you get too much "slop" I have before now carefully straightened the stand for and put a shim washer under the bolt head to keep it tighter.

Thanks Bryan!  A shim between the bolt head and stand, or inside the slot next to the frame lug?  Not sure what a washer next to the bolt head would accomplish if the tangs (is this the correct word?) on the stand are straight and parallel.

I imagine a fair amount of heat would be required for straightening?  Would a propane torch be enough, or are we talking about something stronger, like acetylene?
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on July 20, 2019, 08:55:22 AM
Its been a few years since i did one but memory tells me the thread tightens up to a shoulder on the bolt so the bolt does not "squeeze" the fork tight. This means a shim between bolt head and outside of stand will stop it opening up again.
Propane should be hot enough.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on July 20, 2019, 11:39:49 AM
Its been a few years since i did one but memory tells me the thread tightens up to a shoulder on the bolt so the bolt does not "squeeze" the fork tight. This means a shim between bolt head and outside of stand will stop it opening up again.
Propane should be hot enough.

Ah-so, now I see what you're saying!  That makes sense.  What makes less sense to me is, when this bolt is installed, there's more threads sticking out the inner tang of the stand than are in contact with the tang itself.  Makes me wonder if it's the correct bolt after all..

EDIT: belay my last - I see now that there's missing nut to go along with that bolt...
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on July 21, 2019, 08:17:56 PM
The "Opening Up" of the slot is a fairly common thing to see but with that and wear on the frame lug you get too much "slop" I have before now carefully straightened the stand for and put a shim washer under the bolt head to keep it tighter.

In case you guys haven't figured this out by now, I'm new to this stuff.  I'm visualizing straightening the bent tang with a big hammer, or closing it in a vise, and imagining having it bend at the base where it joins the stand, rather than out near the end where it bent in the first place, so it's still bent outwards at the hole but won't fit back over the frame lug.  I was thinking that finding some kind of frame-tang-width spacer to insert in the gap while straightening the tang would save me from bending any part of it back too far - but then, I imagine that some spring-back would occur and a spacer would prevent getting it straight at all.

What's the best way to approach this?  Heat and a big hammer?  Heat and slow pressure in a vise?
Title: Re: New (to me!) '77 CB400F - US model
Post by: K2-K6 on July 21, 2019, 09:23:49 PM
Agree with Bryan assessment of spacing etc.

Also think your assessment of correction is bang on the money regarding how it's going to go back.

It looks like it's bent from the edge of the hole nearest the blind end of the fork outwards from there ,  but as you suspect,  I think just squeezed back with no support will result in bending at the root of the fork if not supported.

I'd go with a support internally from blind end to start of hole. Then heat the bolt head side directly,  and squeeze it inwards with "vice" grip type tool as you can set it to not pinch too far.

If not hot enough it will spring back,  you'll feel it yeald if temp is high enough and it'll stay put like that.

It's the pointed blue tip in a flame that's hottest,  get that point just touching the surface and it should get to traffic light red which will signal it's hot enough to yeald.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on July 21, 2019, 09:38:15 PM
Thanks for that advice, K2-K6!  I think I'll take it to work and rummage through our remarkable collection of random, odd-sized fasteners and find one with a non-threaded shank that's as close in diameter to the thickness of the frame lug that I can find.  Think something round that just fits in the gap at the root would do the job?
Title: Re: New (to me!) '77 CB400F - US model
Post by: K2-K6 on July 21, 2019, 09:42:58 PM
I think it should do,  it's just trying to stop the force all concentrating on that sharp internal corner where it naturally wants to go.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on July 21, 2019, 09:45:18 PM
I think it should do,  it's just trying to stop the force all concentrating on that sharp internal corner where it naturally wants to go.

(https://advrider.com/f/styles/advrider_smilies/thumb.gif)
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on July 23, 2019, 01:17:09 PM
Just to give you guys an idea of where my head is with this project right now... I was about to ask a cam chain question that was already discussed awhile back on this very thread.  I just noticed that I've twice - on this very same page, even - brought to your attention my thought that the bike might have fallen or been in an accident.  Sorry... :-[
Title: Re: New (to me!) '77 CB400F - US model
Post by: taysidedragon on July 23, 2019, 07:35:02 PM
Just to give you guys an idea of where my head is with this project right now... I was about to ask a cam chain question that was already discussed awhile back on this very thread.  I just noticed that I've twice - on this very same page, even - brought to your attention my thought that the bike might have fallen or been in an accident.  Sorry... :-[

No problem,  with a gear lever that shape there is no doubt!
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on July 24, 2019, 01:15:58 AM
Thanks taysidedragon - I'm mostly just embarrassed by how flaky I'm being about all this.  But it's been a crazy, stressful year and my moto interests have taken a distant back seat.

I'm not sure how I'd straighten that shift lever's twist - a replacement may just be a few dollars away...

https://4into1.com/gear-shift-lever-short-cb-cl-sl-xl100-125-200-250-350-500-cb500-550-650-750/ (https://4into1.com/gear-shift-lever-short-cb-cl-sl-xl100-125-200-250-350-500-cb500-550-650-750/)
(https://cdn1.bigcommerce.com/server5200/jcd9tbp/products/327/images/1017/emgo_gear_shift_lever_honda_83_88010__77907.1355538262.750.750.jpg?c=2)
Title: Re: New (to me!) '77 CB400F - US model
Post by: taysidedragon on July 24, 2019, 11:17:26 AM
If that lever is cheap I would buy it, otherwise fix the old one. A bit of heat and a vice should straighten it, fit a new rubber and it's done.  🔧👍
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on July 24, 2019, 11:43:30 AM
If that lever is cheap I would buy it, otherwise fix the old one. A bit of heat and a vice should straighten it, fit a new rubber and it's done.  🔧👍

It's "only" US$12 (plus shipping, but I was thinking of buying new brake hoses from them anyway).  But, as I'm already going to be working on the side stand with heat and a vise (and probably plenty of vice, too  ;) ), I might as well try the shift lever, too.  Worst case, I destroy it and I'm buying the new one anyway...
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on July 27, 2019, 03:11:18 PM
My ignorance rears its ugly head yet again: regarding using heat to straighten the bent steel side stand and shift lever - should I quench the heated area once I’m done working it to cool it quickly, or should I let it cool down in the air, in its own time?
Title: Re: New (to me!) '77 CB400F - US model
Post by: Moorey on July 27, 2019, 03:38:18 PM
I wouldn't quench as it could make it brittle depending on the steel. The worst that will happen with normalizing is it will slowly bend again over time as it has done now..
Title: Re: New (to me!) '77 CB400F - US model
Post by: K2-K6 on July 27, 2019, 03:45:47 PM
General rule for heating steel is never to quench it after heating, unless you know specifically that you need to change the properties intentionally. 

Heat treatable steel gets harder and more brittle when quenched,  so its a property you'd specifically ask for in that process. That's if it's of that metallurgy.

The gear lever you should be able to do cold ( don't try to bend it when installed though as you risk damage to shaft)  clamp the flat bit vertically in a vice with the rubber bit pointing upward,  not too tight as you are only needing to restrain it, then put an adjustable spanner on the flat piece right next to the rubber and twist it to correct angle.  It'll usually go fairly easily.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on July 27, 2019, 05:13:09 PM
Thanks guys - I was researching heat treating online, and although I understand the processes a bit, I wasn't getting any hints about what was preferable in my circumstance.

I'll try the side stand this afternoon; the gear lever is still on the bike and although I definitely planned to remove it before trying to straightening it, thanks for the reminder - it wasn't uncalled for!  ;)
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on July 28, 2019, 03:13:11 AM
I think this shift lever has been repaired.  Can someone (maybe with the forward US-style foot pegs and non-linkage shift lever) confirm that this isn't the usual honda weld quality?  EDIT: the 4into2 replacement, pictured above, has no weld at all...

Click to zoom if so inclined:

[attach=1]

[attach=2]

[attach=3]
Title: Re: New (to me!) '77 CB400F - US model
Post by: taysidedragon on July 28, 2019, 12:09:54 PM
That looks similar quality welding to what's on my UK gear lever.
There's chrome over the weld so probably original.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on July 29, 2019, 02:37:33 AM
Well there you go.  I just assumed that the OEM would have been a one-piece casting like that after-market job, and therefore my welded one must have been broken and repaired.

I bent it "back" to where it looks like it should be right, but without the bike present, it's hard to know!  We'll find out soon - easy enough to fine tune it later...
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on August 31, 2019, 11:00:58 PM
I went to a local museum's classic motorcycle meet today; saw three CB400F's there, but all earlier than '77.  That late model US version really is the ugly bastard child, isn't it?  Fugly tank, upright bars and forward pegs...  anyway, I wonder if the owner of this one knows what a gold mine he has with those OEM headers in such great shape?

[attach=1]
Title: Re: New (to me!) '77 CB400F - US model
Post by: 10tenmen on September 01, 2019, 08:59:43 AM
How do you know they are genuine bars ie what’s the giveaway sign thanks.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on September 01, 2019, 12:17:39 PM
How do you know they are genuine bars ie what’s the giveaway sign thanks.

Well, now that you mention it... I don't know they're original.  Although he acknowledged that the silencer wasn't OEM, he said the headers were, so I'm taking him at his word.

They do look rather shinier than the rest of the bike don't they?
Title: Re: New (to me!) '77 CB400F - US model
Post by: 10tenmen on September 01, 2019, 12:51:32 PM
Agreed like you say if original they are valuable lol.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on September 01, 2019, 09:53:14 PM
While digging into my fuse block to help with a wiring question, I found this (click to zoom):

[attach=1]

To be honest, I didn't dig further and I'm not sure which "side" of the fuses this little bodge is on, but I know enough about how electricity moves through conductors to know that this isn't cricket!  The only reason I can come up with for this is perhaps the clips holding the fuse ends weren't gripping securely, so the wire pulls them tight.  Pardon my Français, but really, WTF?!?

It looks like the same kind of job done to hold the ignition switch connector to the broken switch: http://www.sohc.co.uk/index.php/topic,17461.msg153957.html#msg153957 (http://www.sohc.co.uk/index.php/topic,17461.msg153957.html#msg153957)
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on September 14, 2019, 03:48:55 PM
No response to my latest post, so just to be sure: that fuse box bodge is an electrical problem... isn't it?
Title: Re: New (to me!) '77 CB400F - US model
Post by: K2-K6 on September 14, 2019, 04:36:09 PM
Take it you mean just the twisted wire there?

Looks like it's been initiated to cope with intermittent connection as you suspect.  Wouldn't in itself do anything wrong if on supply side but would increase fuse rating if on outbound terminals.

(I use a jumper in that location to get a car fuel pump going by taking a supply from cigarette lighter circuit in the event of problem failures)

Looks like the fuse board has problems causing no start or complete stopage on occasion.  In cricket terms "light stops play"  ;D
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on September 14, 2019, 05:12:23 PM
Take it you mean just the twisted wire there?

Looks like it's been initiated to cope with intermittent connection as you suspect.  Wouldn't in itself do anything wrong if on supply side but would increase fuse rating if on outbound terminals.

Thanks K2-K6... your "ifs" got me thinking about that, too, so I removed the fuse block to actually examine which wires on which side of the fuses were shorted.  As it turns out, that twisted wire is connecting the black/red and the brown/blue wires.  Looking at the UK wiring diagram, I believe this would create a short circuit between the "park" and "headlight" positions of the lighting switch on the right handlebar control, so any position other than "off" would illuminate them all.

But this is a US spec bike, with no light switch, which is wired to have the headlight always on when the ignition switch is on - except when the electric start button is being pressed - at that point the headlight is supposed to go off until the starter button is released.  With a short across those two wires, the headlight will always stay on, even when the electric starter is being used, bypassing the protections built into the circuit... such as they are.

I think I'll fix it...  ;)
Title: Re: New (to me!) '77 CB400F - US model
Post by: K2-K6 on September 14, 2019, 05:47:38 PM
I feel it's definitely worth while to get it properly sorted and debugged,  just makes using it easier too.

I'd do the same.
Title: Re: New (to me!) '77 CB400F - US model
Post by: Lobo on September 16, 2019, 01:23:29 AM
... whilst I don’t have the US wiring diagram mattsz, I’m not sure how connecting the Park & HL will bypass the starter button ‘protection’ - ie I’d have thought the ‘protection’ will continue to work as designed?
My guess at this bodge is that there’s been a break in the Black/Red feed (to the fuse holder) ... and so the PO has jumped the two together.

Has the PO therefore solved the problem and (lazily) restored the lighting to normal road light functioning?  (at the expense of proper Park light function)

Simon.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on September 16, 2019, 12:13:19 PM
... whilst I don’t have the US wiring diagram mattsz, I’m not sure how connecting the Park & HL will bypass the starter button ‘protection’ - ie I’d have thought the ‘protection’ will continue to work as designed?

Perhaps "protection" wasn't the best choice of words - substitute "function?"  USA model headlights are always on when the ignition key is on - except when you push the starter button - power to the headlight is then temporarily disconnected until the starter button is released.  So the circuit's "function" is to remove the electrical load of the headlight while the starter is used.  Whether that's a "protection" could be debated, I suppose.  Whatever you call it, with that jumper shorting the two wires in question, the headlight would stay on when the starter button is pressed, which is not the intended design.  I think...  ;)

BTW, if you're at all interested, I've added my version of the USA-spec wiring diagram to the same post that has the UK-spec diagram... link to that thread: http://www.sohc.co.uk/index.php/topic,17969.msg155929.html#msg155929 (http://www.sohc.co.uk/index.php/topic,17969.msg155929.html#msg155929)

Quote
My guess at this bodge is that there’s been a break in the Black/Red feed (to the fuse holder) ... and so the PO has jumped the two together.

Has the PO therefore solved the problem and (lazily) restored the lighting to normal road light functioning?  (at the expense of proper Park light function)

Thinking about it, I'm liking this idea - you may or may not recall that my starter switch was broken, and it wouldn't operate the starter properly (pic of the switch in this post: http://www.sohc.co.uk/index.php/topic,17599.msg153989.html#msg153989 (http://www.sohc.co.uk/index.php/topic,17599.msg153989.html#msg153989)).  Full headlight current runs through that switch - the "break in the Black/Red feed (to the fuse holder)" you mentioned could very well have been that broken switch - and I wouldn't have realized it because the headlight was getting power through that bodge...
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 09, 2019, 01:13:20 PM
Sorry for my shameless cross post - I posted a question of sorts in the tricks and tips section, which has had 80+ views to date but no replies.  Anyone care to take a look and comment?

http://www.sohc.co.uk/index.php/topic,20253.msg179895.html#msg179895
Title: Re: New (to me!) '77 CB400F - US model
Post by: Nurse Julie on October 09, 2019, 03:17:39 PM
Sorry for my shameless cross post - I posted a question of sorts in the tricks and tips section, which has had 80+ views to date but no replies.  Anyone care to take a look and comment?

http://www.sohc.co.uk/index.php/topic,20253.msg179895.html#msg179895
A soda blaster has many uses, including the parts you are talking about. No media is left, so no issues with little bits if glass or sand being left but, it is a slow process blasting anything with soda. The outcome and time spent is entirely dependant in the output of the compressor you are using. It needs to be a high CFM rating to do an effective job.
Title: Re: New (to me!) '77 CB400F - US model
Post by: Lobo on October 09, 2019, 10:08:55 PM
...yea, I’ve read this ‘tip’ before Oddjob, noting that jumper wire was not in fact needed; you simply took two fuses out and rammed one back into in the ‘dead space’ between the holders. (and like you I can’t remember which two - but it wouldn’t be hard to work out)
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 09, 2019, 10:57:14 PM
Sorry for my shameless cross post - I posted a question of sorts in the tricks and tips section, which has had 80+ views to date but no replies.  Anyone care to take a look and comment?

http://www.sohc.co.uk/index.php/topic,20253.msg179895.html#msg179895
A soda blaster has many uses, including the parts you are talking about. No media is left, so no issues with little bits if glass or sand being left but, it is a slow process blasting anything with soda. The outcome and time spent is entirely dependant in the output of the compressor you are using. It needs to be a high CFM rating to do an effective job.

Thanks Julie!  Where does the baking soda go?  Or, do you have to wash the parts and the soda dissolves?  I guess the junk you're blasting off has gotta be clean off somehow...

The specs on that tool are, ahh... interesting.  The website lists the "average air consumption as 7 cubic feet/min @ 90psi... which is also the maximum pressure...
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 09, 2019, 11:02:49 PM
The thing with the twisted wire makes me wonder if the bike has ever been stolen?

Ooooh, the plot thickens!  While this is certainly an intriguing possibility, I doubt it's the case.  The bikes previous ownership history is pretty well known, and the same type of wire that was jumping the fuses was also holding the broken ignition switch together (physically, not electrically).  I really like the "bypassing the broken headlight switch" theory - but that said, anything is possible!!!
Title: Re: New (to me!) '77 CB400F - US model
Post by: Nurse Julie on October 09, 2019, 11:16:57 PM
Sorry for my shameless cross post - I posted a question of sorts in the tricks and tips section, which has had 80+ views to date but no replies.  Anyone care to take a look and comment?

http://www.sohc.co.uk/index.php/topic,20253.msg179895.html#msg179895
A soda blaster has many uses, including the parts you are talking about. No media is left, so no issues with little bits if glass or sand being left but, it is a slow process blasting anything with soda. The outcome and time spent is entirely dependant in the output of the compressor you are using. It needs to be a high CFM rating to do an effective job.

Thanks Julie!  Where does the baking soda go?  Or, do you have to wash the parts and the soda dissolves?  I guess the junk you're blasting off has gotta be clean off somehow...

The specs on that tool are, ahh... interesting.  The website lists the "average air consumption as 7 cubic feet/min @ 90psi... which is also the maximum pressure...
The baking soda is water soluble so a rinse in water will sort that. The spec on that tool is nowhere near man enough for the job, you would need 14 CFM at an absolute minimum and that one is only 7 CFM. The CFM is more important than the PSI for blasting any media.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 10, 2019, 01:57:33 AM
The spec on that tool is nowhere near man enough for the job

(https://advrider.com/f/styles/advrider_smilies/ImaPoser.gif)

I'll save my money...
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on October 25, 2019, 04:44:44 PM
As I mentioned in another thread, I finally removed my broken silencer - despite copious application of heat and penetrating oil over a long period, I just couldn't budge it without making it even worse - if it's possible!  I couldn't grip the body, since it was already separated from the connecting end, and any, ahhhh... forceable persuasion... just served to bend and deform the collar where it joins the collector.  I literally had to peel the collar away to get it free.  Pics... the original break is obvious:

[attach=1]

[attach=2]


An additional hole in the bottom at the rear, which I didn't even know was there:

[attach=3]


The collector end, with the graphite-like "gasket" which suffered a bit in the removal as well:

[attach=4]


Anyway, based on all that, I decided not to try and repair it.  The usual aftermarket silencer supplied by DSS is out of stock - not like I'm in any hurry for it anyway.  Matt at their USA location said that they'd have a new supply of these after the new year.  But then he got back to me and said they had a discounted one in stock with a couple of dents, which would be visible when mounted.  I don't think I'll regret the tradeoff, since I'm not doing a fancy restoration, and just want to get it running, so I bought it, along with a couple of other items on my list.   The savings just about paid for the extra bits and the shipping...
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bradders on October 25, 2019, 05:52:25 PM
That’s the same place that mine has corroded Mattsz although I don’t think mine is quite so bad as yours. In fact the chrome comes up quite nice with a polish. Also I think my baffles are breaking up as the silencer rattles as you move it.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on February 02, 2020, 09:46:02 PM
The 400 is being stored in a heated shop for the winter!  8)

But it's 1/2 an hour from me...  :(

I went up there today, to poke at a few things - forgot to bring the key with me, so electrical tests were a hassle!  Reinstalled my now-unbent rear turn signal bracket; tested the light but it wouldn't work.  Turns out the bulb was fried - nice and cloudy.

Could it be the original?  How long has it been since Stanley made bulbs?

 [attach=1]

Inside the same turn signal housing, the plastic's "chrome" lining is peeling off in sheets - I wonder if the bulb's hazy failure is related?
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on February 02, 2020, 09:57:25 PM
Stanley are still in production and that milky colour is caused by air leaking into the envelope
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on February 02, 2020, 10:56:16 PM
The guy I bought my Sylvania replacement bulbs from said Stanley hasn't made bulbs for years... maybe he just hasn't sold them...
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on March 25, 2020, 11:08:09 PM
The 400 is being stored in a heated shop for the winter!  8)

But it's 1/2 an hour from me...  :(

Went to fetch the wee Honda today!  It wasn't very happy to leave its winter home, I'm sure! (see attached) I'm looking forward to cleaning it up and reassembling it and try to get it running!

Oddly, after sitting for over a year with hardly a drop of oil on the floor, I found it today with a couple of puddles beneath it.  Not much, about a half-teaspoon between the two - but I wonder why it's decided to weep just over the last six weeks?

[attach=1]
Title: Re: New (to me!) '77 CB400F - US model
Post by: taysidedragon on March 25, 2020, 11:40:35 PM
It did an excited wee because it was going home. 😂
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on March 26, 2020, 12:56:28 AM
It did an excited wee because it was going home. 😂

(https://advrider.com/f/styles/advrider_smilies/ImaPoser.gif)

It was better off where it was - now it's relegated to a corner of an unheated garage.  But at least it will get some attention...
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on April 13, 2020, 06:16:31 PM
I have a question regarding the individual choke plate adjustments.  There's some lash in the system, so when the choke is in the closed (for cold starts) position, the #1 plate is completely closed, and each successive plate remains a little more open than the last.  When I open the choke fully (running position), each plate is mostly open, but a little less than its neighbor to the left.  This is how they came to me (click on photo to zoom in):


[attach=1]


I've been messing with the adjustments - I can't seem to get all the plates to be open and closed the same amount.  Is it better to set them so they all close perfectly together, but end up in slightly different positions when open (per above photo)?  Or better to set them so they all open exactly the same amount, but don't all quite completely close with choke?
Title: Re: New (to me!) '77 CB400F - US model
Post by: taysidedragon on April 13, 2020, 07:02:17 PM
I'm no carburation expert, but I would set them all equal when fully open. That's where they run for most of the time, choke only on for a short time.
Where is the lash in the system, strange they are not moving together?
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on April 13, 2020, 07:17:45 PM
I'm no carburation expert, but I would set them all equal when fully open. That's where they run for most of the time, choke only on for a short time.

Thanks!  I was thinking the same...

Quote
Where is the lash in the system, strange they are not moving together?

I'll show you, let me get a photo...
Title: Re: New (to me!) '77 CB400F - US model
Post by: Laverda Dave on April 13, 2020, 07:57:37 PM
Mine are the same on both 400/4's. The lash or lack of adjustment appears to be in the choke linkage assembly on each carb (the flat blade screw with the locknut). If you get no.1 carb choke closed you loose a bit on no. 2 and it subsequently gets worse on no.3 and no.4. Your 4th carb looks particularly bad though, do you have any adjustment left?
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on April 13, 2020, 07:59:13 PM
The choke lever turns the choke plate shaft on carb 1.  There's an adjustable linkage between the shafts of carbs 1 & 2.  Another adjustable linkage between the shafts of carbs 2 & 3, and another between 3 & 4.  See photo:


[attach=1]


Each of the linkages on my rack were adjusted with a little gap between the set screw and stop.  So, choke 1 plate had to rotate a bit before choke 2 plate began to do the same.  Choke 2 plate had to rotate a bit before choke 3 plate began to move.  And so on - by the time choke 1 plate was fully open, choke 4 plate had a ways to go - as seen in the photo a couple of posts back.

I don't know if mine are normal, or if there's something wrong with the mechanism, but I can't adjust them so they all open together as a unit and close together as a unit, ending up in the same positions at each extreme of travel.  Hence my question about which choice is the better one.

Having changed the adjustment for equal open position, you can see the above photo also kind of shows how, when the choke is closed, even though the #1 choke plate is fully closed, each successive choke plate remains open a bit more than its neighbor to the left.

Here's a pic of the readjusted plates in the open position - all the same (compare to the photo a couple posts back)...


[attach=2]
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on April 13, 2020, 08:53:40 PM
I am probably wrong but i thought there was a spring in each adjuster
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on April 13, 2020, 10:30:13 PM
I am probably wrong but i thought there was a spring in each adjuster

Each choke plate shaft has a spring forcing it closed.  Tightening each adjustment screw pushes the plate "open."  I think...  I just did it a couple of hours ago, and I've already forgotten...  :-[
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on April 13, 2020, 10:43:49 PM
Some observations...

All four float bowl o-rings were glued securely in place with plenty of some sort of goop.  Will have to clean them all off...

[attach=1]


#4 float bowl has a mismatched screw - bigger head, and shorter thread which is somewhat stripped at the end (although the pic doesn't really show it).  The proper screws seem to work in all four positions (carb body thread isn't damaged), so I'll get a correct replacement...

[attach=2]
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on April 13, 2020, 11:30:12 PM
While we're playing with 400 carbs, I have another choke operation question.

There's a cam-driven linkage which appears to tie the choke to the throttle.  As mine is currently adjusted, when the choke is open (normal operation), there is a gap between the choke lever linkage and the adjustable set screw on the throttle mechanism:

[attach=1]


When the choke is closed, the cam shifts the linkage slightly - in theory, I suppose, to push on the adjustment screw and open the throttle a bit:

[attach=2]


Mine is currently adjusted so when the choke is closed, the linkage just touches the adjustment screw - but it doesn't actually open the throttle at all.  Is it supposed to open the throttle?  My copy of the service manual doesn't mention it...
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on April 14, 2020, 01:44:08 AM
I've spent a good long while reading through carb cleaning posts - not finding anything definite: I'm hoping to clean all the carb bits I've removed from inside the float bowls - I haven't split the carb rack or opened the top covers.  What's the best way to do this?  Any particular solvents better than others?  I have carb cleaner spray, and some cans of solvents, including mineral spirits (paint thinner), lacquer thinner, acetone, kerosene (paraffin for you blokes?), even alcohol.  I could buy a gallon-can of liquid carb dip, but it's not cheap.

I wasn't planning on any kind of major soak for the four attached carb bodies, but I'll need to clean the undersides of the carbs and all the passages (spray for that, I guess)...
Title: Re: New (to me!) '77 CB400F - US model
Post by: taysidedragon on April 14, 2020, 10:54:10 AM
Carb cleaner spray and use of an old toothbrush cleans up the carb bodies ok.

To clean all the passages and jets it's best to use an ultrasonic cleaner. Check passages are clear afterwards with air jet can (computer type) or carb cleaner spray. No prodding with wire!
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on April 14, 2020, 11:27:31 AM
Carb cleaner spray and use of an old toothbrush cleans up the carb bodies ok.

To clean all the passages and jets it's best to use an ultrasonic cleaner. Check passages are clear afterwards with air jet can (computer type) or carb cleaner spray. No prodding with wire!

Thanks!  Not even thin copper wire?  This seems a fairly common procedure.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on April 14, 2020, 11:31:37 AM
While we're playing with 400 carbs, I have another choke operation question.

There's a cam-driven linkage which appears to tie the choke to the throttle... 

Never mind... I found this on page 7 of the factory manual:

[attach=1]

Clearly mine is not correctly adjusted.

Even with my carbs sitting on the bench, I'm not sure I can reach that adjustment with any tools I currently have.  I certainly can't imagine being able to do it with everything assembled on the bike... must be possible, though...
Title: Re: New (to me!) '77 CB400F - US model
Post by: Laverda Dave on April 14, 2020, 12:44:18 PM
Looking at your re-adjusted carbs with the chokes open is about right.  As Taysidedragon mentions, they are normally open 95% of the time so that is where you want the adjustment to count.  As an aside, when I start my bike on full choke I have to open the choke a fair amount once the engine has started otherwise it races up to 3000RPM.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on April 14, 2020, 06:22:08 PM
Looking at your re-adjusted carbs with the chokes open is about right.  As Taysidedragon mentions, they are normally open 95% of the time so that is where you want the adjustment to count.  As an aside, when I start my bike on full choke I have to open the choke a fair amount once the engine has started otherwise it races up to 3000RPM.

The spec for that fast idle setting appears to be 3500 - 4500 rpm... seems quite high to me, but Honda must know what they're up to...
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on April 15, 2020, 12:56:25 AM
There's a thin layer of brown residue covering most everything that touched fuel in the carb bowl.  Simply soaking the brass bits in lacquer thinner doesn't do much; I can scrub it off with a cab-cleaner-spray soaked rag.  But the stuff doesn't scrub off the plastic floats; I can, however, scratch at it with my fingernail!

[attach=1]

I didn't soak the floats, which I think might help - can I safely soak them in the lacquer thinner or carb cleaner, without fear of melting them?
Title: Re: New (to me!) '77 CB400F - US model
Post by: taysidedragon on April 15, 2020, 11:22:19 AM
I only used carb cleaner and wd40 on mine. I was afraid to use anything stronger in case of damage.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on April 21, 2020, 04:59:33 PM
I only used carb cleaner and wd40 on mine. I was afraid to use anything stronger in case of damage.

Thanks...
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on April 21, 2020, 05:03:16 PM
More minor progress... I went to change the front tire, and found a few rusty spots inside the rim.  I thought I'd scrub off the rust and maybe spot prime them?

[attach=1]
Title: Re: New (to me!) '77 CB400F - US model
Post by: taysidedragon on April 21, 2020, 05:11:25 PM
That rim looks pretty good. Much, much better than what I found on mine when I took the tyres off. ☹
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on April 21, 2020, 05:43:29 PM
That rim looks pretty good. Much, much better than what I found on mine when I took the tyres off. ☹

Small victories, then! 

Here's a photo of a rim off my bought-brand-new Royal Enfield, taken when the bike was only a year old with only 2000 miles on the clock:

[attach=1]


Does my touch up and spot prime idea sound like a suitable one?
Title: Re: New (to me!) '77 CB400F - US model
Post by: taysidedragon on April 21, 2020, 06:18:38 PM
That rim looks pretty good. Much, much better than what I found on mine when I took the tyres off. ☹

Small victories, then! 

Here's a photo of a rim off my bought-brand-new Royal Enfield, taken when the bike was only a year old with only 2000 miles on the clock:

(Attachment Link)


Does my touch up and spot prime idea sound like a suitable one?

I don't see why not.  👍
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on April 21, 2020, 06:58:16 PM
I don't see why not.  👍

 ;D
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on April 27, 2020, 07:31:52 PM
I''ve turned my attention to the rear wheel - I removed it, and find that when I turn the bearings (and the spacer between them) there's kind of a "crunchy" feel - I'd say the bearings need to be replaced, if they can't be cleaned and re-greased.

I struggled to remove the sprocket circlip, but got it in the end.  Everything is pretty rusty, but it's more like light surface rust, or even a rust-colored fine dust.  Two of the sprocket bolts freely separate from the damper bushes, two are very stuck.  I tried placing a spacer over them and using the sprocket nut to draw the bolt out, but the dampers just stretch and the bolt doesn't budge.  So I've put some penetrating oil to them and am letting them rest for now.


[attach=1]


I'm thinking I should clean up the mess - any advice about how to deal with the sprocket bolts?  Can I try to twist them out using the flats that seat in the sprockets?  Or does that put the rubber bushings in jeopardy?  Should I just leave them alone?


I'm working on the wheels because I know the bike needs new tires and chain - and probably sprockets, and probably rear wheel bearings (if not front as well).  These are things I can bring to work with me to work on in spare moments.  But I still don't know how well, or even if, the engine works, so I wonder if I'm putting the cart before the horse?  I'll change the tires because I can, and I have them ready, but I'm thinking I'll hold off on the chain, sprockets and wheel bearings until I know the engine is usable.  On the other hand, the rear wheel obviously needs attention, and it's something I can do now, whereas I can't work on the engine during my work weeks. 
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on April 27, 2020, 07:38:27 PM
By the time you have the bearings out, and the way you have to get them out does them no favours either, you may as well buy generic and replace them
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on April 27, 2020, 07:41:44 PM
By the time you have the bearings out, and the way you have to get them out does them no favours either, you may as well buy generic and replace them

Thanks!  I figured they were a consumable item - but I've had a couple of bikes with some bearings that had a cleaning and regreasing maintenance schedule.  Not wheel bearings, though...

What do you think about the stuck sprocket bolts, Bryanj - leave them for now, or try to force them out?
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on April 27, 2020, 08:43:30 PM
Never had that problem, but also havent done many 400 since i left trade 40 yrs ago!
Unless Julie knows different i would be tempted to leave them alone unless they absolutely have to come out
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on May 24, 2020, 11:01:36 PM
I'm cleaning things up - there's a thick coating of chain lube all over everything on the left side, so I decided to remove the swing arm for better access.  It came out easily, but took a long time to clean up using just mineral-spirits soaked rags!

Should the "pivot tube" (which the big bolt goes through) rotate in the swing arm?  I see the grease fitting - what's inside there?  If I start adding grease, will it come out the sides around that tube?
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on May 24, 2020, 11:09:08 PM
Speaking of removing the swing arm...

I discovered another bodge when I was removing the shocks - the upper mountings for each one are different, and neither has even close to the correct hardware.  I think the left shock may be done for, it looks like oil has been leaking out:

[attach=1]


The right side has a bizarre collection of hardware - a thin brass washer, a too-big threaded nut (looks like the type that secures an electrical switch in a panel) serving as a spacer, a knurled threaded "nut" (looks like something removed from a table lamp's electrical fixings) also serving as a spacer, then - finally! - an acorn nut:

[attach=2]

[attach=3]


The left side frame mount doesn't even have a threaded stud - there's a threaded hole where the stud should be.  A bolt and two spacer washers secure the shock.  I wonder if it broke and someone drilled and tapped for the bolt, the thread isn't the same as the stud on the right side:

[attach=4]

[attach=5]


Any reason to be concerned about this for the time being?
Title: Re: New (to me!) '77 CB400F - US model
Post by: taysidedragon on May 25, 2020, 12:04:07 AM
The missing stud on left hand side is a worry. A bolt into a shallow threaded hole is not as strong or secure. You could possibly find yourself riding on only one shock.
A good engineering shop should be able to repair that back to standard.
The dome nuts are longer than a standard size nut, hence the spacers. David Silver sells them.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on May 25, 2020, 12:12:19 AM
The missing stud on left hand side is a worry. A bolt into a shallow threaded hole is not as strong or secure. You could possibly find yourself riding on only one shock.
A good engineering shop should be able to repair that back to standard.
The dome nuts are longer than a standard size nut, hence the spacers. David Silver sells them.

Thanks taysidedragon!

The threaded hole is 7/8" deep.  Not what I'd call shallow - I wouldn't worry about the bolt pulling out, but I do think about the possibility of the whole spindle snapping off if it's "walls" are too thin after being drilled and threaded...
Title: Re: New (to me!) '77 CB400F - US model
Post by: taysidedragon on May 25, 2020, 12:27:28 AM
I didn't realise you had that much left to bolt into. I assumed it had snapped of at the frame.
It doesn't sound strong enough to me as it is. 🙁
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on May 25, 2020, 01:09:21 AM
I didn't realise you had that much left to bolt into. I assumed it had snapped of at the frame.
It doesn't sound strong enough to me as it is. 🙁

No, the "spindle" that the shock bushing fits on is still there.  More like just the threaded part broke off and someone drilled and threaded it.  Here it is with the bolt partially inserted:

[attach=1]


How should this be repaired?  Cut the whole spindle off and weld up a new one?  Would the new one - spindle and threads - be machined from a single piece, or does a stud get threaded in, kind of like was done here?
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on May 25, 2020, 06:12:29 AM
Me, i would make stud with the thread on the spigot one end and long enough to bottom out fitted with the best locktite and the correct thread on the visible part.
That "stepped" nut was for a carrier of some sort
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on June 01, 2020, 05:53:29 PM
I'm at a bit of a standstill waiting for a few parts... I finally got the electric start up and running so I decided to cross my fingers, hold my breath, and do a compression test.  Should have done it a lot sooner, although I don't know if it would have mattered.  My results are most disappointing...

I tried it with all the plugs out, to go easy on the motor and battery - all four read only in the 72 - 78 psi range.  That's right, 100 psi less than they should be.  Next I tried it with all the plugs installed - excepting the cylinder being tested, of course - and found no change.  I added a little oil, against ring leakage, which bought them up just a few points.  I tried loosing all the tappets, against valve leaks due to bad adjustment, which brought them up to the 91 - 95 psi range... better, but still nowhere close. I pulled the head cover and tried re-torquing the head, against a leaky head gasket due to a loose head (all the head nuts were tight except for the two "pillar nuts," which moved a little bit), but this made no change.  While I had the cover off, I checked the cam timing, just in case - the marks on the sprocket are just where they should be with the "T" mark on the spark advancer aligned with the matching mark...

To rule out a faulty compression tester, I tried a borrowed one, which matched mine's readings.  I also hooked my tester up to my air compressor, and found it's readings within 5 psi of the compressor's regulator gauge.

Things aren't looking too good for our hero...
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on June 01, 2020, 05:58:28 PM
Its not been run for so long get it going and see what happens
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on June 01, 2020, 06:01:04 PM
Its not been run for so long get it going and see what happens

It's been about 2 years.

I was going to ask whether it was a good idea to try it first, before "writing it off" and opening up the engine...
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on June 01, 2020, 06:56:59 PM
As you can take the top off in the frame i would try and get it to run, probably bolting on the absolute minimum
Title: Re: New (to me!) '77 CB400F - US model
Post by: K2-K6 on June 01, 2020, 10:26:05 PM
I'm with trying to start it too,  give the little guy a chance  ;D

First it may be worth spinning it with plugs out and wd40 down the bores to help if there's any long term oil gumminess in the rings.

If it runs,  let it warm a bit, plugs out,  carbs open and retest for compression then. See what you've got as it'll tell you one way or the other if it stays low as to further decisions.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on June 01, 2020, 10:32:10 PM
I'll probably do that... put it together enough to run it and give it a chance... just to satisfy my curiosity, if nothing else!
Title: Re: New (to me!) '77 CB400F - US model
Post by: Lobo on June 01, 2020, 10:38:27 PM
Matt - haven’t fully read the previous 23 pages of this post - ie forgive me, but are you performing the compression test correctly ie with the throttle wide open? (and plugs out). Page 1 says your bike has 22k miles (ie barely run in!) and it seems odd all 4 cylinders are ultra low .... and yet within a few psi of each other....

Simon

Addendum... and Air filter removed.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on June 01, 2020, 10:45:48 PM
Matt - haven’t read the previous 23 pages of this post - ie forgive me, but are you performing the compression test correctly ie with the throttle wide open? (and plugs out). Page 1 says your bike has 22k miles (ie barely run in!) and it seems odd all 4 cylinders are ultra low .... and yet within a few psi of each other....

Simon

Simon - very good question!  I've actually let some of the details on this slide a bit, as my recent posts here have drawn little comment (with a few exceptions, of course - you know who you are, thank you!).  No surprise, I suppose; I've done a lot of talking, but not taken much action in the past year-and-a-half.  I'm getting bored of me!

I should have said: the carbs are currently off the bike, as is the silencer.  I have four open carb insulators, and an open exhaust collector...
Title: Re: New (to me!) '77 CB400F - US model
Post by: Lobo on June 02, 2020, 06:07:09 AM
...that’s bad news; I’m no mechanic but frankly surprised all 4 readings the same given the significant loss of compression.
Hopefully this implies ‘good news’ - ie nothing mechanically buggered.
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on June 02, 2020, 06:54:00 AM
It could be rings stuck in grooves and in all honesty it could go either way in get it running and hot , all frees up and then runs fine OR get it running and hot they stay stuck and it runs like shite. Either way i think its worth trying
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on June 02, 2020, 11:55:56 AM
Thanks for the input, guys.  I guess I can only try it and see what happens.

The history is as follows: I rode the bike in the summer of 2015.  It seemed to run ok then, decent power up to the red-line at least, anyway.  The PO rode it a couple hundred miles next summer, 2016.  It was stored in an unheated garage from the fall of 2016 through fall of 2018.  The guy who stored the bike said he drained the fuel tank, but not the carbs, and that he "kicked it over a few times" during that period, but I have no idea what that really means.  When I got the bike in 2018, I examined the dipstick oil and found it clean and clear, removed the plugs and squirted some oil in the cylinders, then kicked it over myself and found it to spin freely.  I buttoned it up and put it away.  It spent the winters of 2018 and 2019 in two different heated garages.

Stuck rings are certainly a possibility, the cause being rust also a possibility.  Just giving some recent background.  Wondering... how often does an engine's compression fail this badly, but also uniformly across all four cylinders simultaneously?
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on June 02, 2020, 02:21:02 PM
One big problem is the legth of flexible hose on the compression tester, i know you tried 2 testers but if they had about the same hose legth it could be your problem. The space left in head when piston at tdc is not much and could easily be doubled.
Thats one reason i say try it and see
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on June 02, 2020, 02:39:00 PM
One big problem is the legth of flexible hose on the compression tester, i know you tried 2 testers but if they had about the same hose legth it could be your problem. The space left in head when piston at tdc is not much and could easily be doubled.
Thats one reason i say try it and see

Yes, that thought entered my head as well.  Both the testers I tried had similar 12-inch-ish length rubber hoses.  I've read posts espousing that effect on the US site, but I've heard other smart people reject that theory with arguments that sounded very convincing to me, partially ignorant as I am to the finer points of internal combustion engines.  I do find the uniform nature of my test numbers to be suspicious.

Is it a linear relationship?  If the tester is doubling the "compressed" chamber volume, would that imply a reading of one-half the normal value could be expected?

EDIT: I just tried the "thumb test" on cylinder #4 - did my best to get a good seal, cranked it over... it blows right by my thumb.  I folded up a "latex" glove to help get a better seal, and tried again with enough force to cause discomfort to my thumb... I may have been able hold against the compression, but not sure.  Does this suggest anything?
Title: Re: New (to me!) '77 CB400F - US model
Post by: K2-K6 on June 02, 2020, 03:15:48 PM
Where is the release valve on the test gauge?

As Brian says the tube will be part of the volume ( and give problems of reading) if the control valve is away at the gauge end of the tube as the tube volume is then evacuated at each exhaust stroke.

If valve is located right where the spark plug location is,  then the tube remains charged and should then report peak psi,  which should be close to specified data for the engine.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on June 02, 2020, 03:19:19 PM
Where is the release valve on the test gauge?

As Brian says the tube will be part of the volume ( and give problems of reading) if the control valve is away at the gauge end of the tube as the tube volume is then evacuated at each exhaust stroke.

If valve is located right where the spark plug location is,  then the tube remains charged and should then report peak psi,  which should be close to specified data for the engine.

The release valve on both the testers I used is located at the base of the gauge, not at the engine end.  I guess the volume of the gauge should be considered as well...
Title: Re: New (to me!) '77 CB400F - US model
Post by: K2-K6 on June 02, 2020, 03:44:38 PM
Looks like your error is there.

Just a rough guess from generally available gauges would suggest pipe volume similar to combustion volume above piston.

Shot in the dark estimation,  150 psi true effective reading would be somewhere near current status  ;D that's my first "range finder" any advances ?
Title: Re: New (to me!) '77 CB400F - US model
Post by: K2-K6 on June 02, 2020, 03:53:54 PM
For reference,  I've had this type for more years than I care to remember

[attachimg=1]

That tag showing at the end is the Schrader valve to reset the gauge and evacuate the previous pressure. Bit of a pain to use,  no sophistication as you have to hold it in tight and get someone else to crank it if you can't reach the button. But always reliable.
Title: Re: New (to me!) '77 CB400F - US model
Post by: Nurse Julie on June 02, 2020, 04:03:05 PM
I have seen someone in the USA test for equal compression across all four cylinders by dropping the exhaust headers off and placing a ping ping ball (table tennis ball) in each exhaust port. Crank the engine over on the kick start and if all the balls hit the garage wall at the same time, compression was close enough to equal to not worry about it 😁😁😁😁😁
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on June 02, 2020, 04:06:18 PM
I have seen someone in the USA test for equal compression across all four cylinders by dropping the exhaust headers off and placing a ping ping ball (table tennis ball) in each exhaust port. Crank the engine over on the kick start and if all the balls hit the garage wall at the same time, compression was close enough to equal to not worry about it 😁😁😁😁😁

 ;D

Equally low is my concern...
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on July 01, 2020, 11:51:46 AM
Ok, so I've decided for the moment to deal with the possible low compression using an old tried and tested tool: denial.  I'll revisit the issue if I find problems with it after I try to get it running.

I've moved on to the oil - draining it, specifically, to inspect and clean the oil pan and strainer, and also to remove the clutch cover and examine the release mechanism (the subject of another thread).

This job has progressed like most of the others - the drain plug must have been last installed by Eddie Hall.  I needed quite a long breaker bar extension to loosen it; remarkable, really, that the threads were never stripped.  What I assume is an aluminum washer on the plug seems to have been crushed so tightly that it and the plug are now permanently joined...

[attach=1]

[attach=2]


The oil filter bolt has been abused - but it wasn't overly-tightened, and a 6-point socket fit it and removed it easily...

[attach=3]
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on July 01, 2020, 11:58:11 AM
While the old oil that I could see (lifted on the dipstick, pumped up to the cam shaft when cranking the engine over) looked clean, I found it wasn’t really so.  The drained oil was pretty black, as was the filter.  The filter cover had some dark residue settled in it - bearing material?  combustion products?  both?

[attach=1]

[attach=2]


The oil pan itself came off easily, no overtightened bolts.  Of course, I couldn’t access them all with the exhaust in place, so the headers had to come off (except for the common surface rust around the tops, the rest looks good, including the collector).  There was a fair amount of the dark residue in the pan as well; not sure how it compares to some others I’ve seen… recall the bike shows 26k miles, and the cam shaft bearing surfaces look pretty good - haven’t laid eyes on the crank bearings though…

[attach=3]

[attach=4]

[attach=5]
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on July 01, 2020, 12:01:49 PM
I dredged the oil pan muck for debris - here’s what I found.  The flecks on the rag remained after the black oily residue soaked in - metallic looking, but seemingly more like paint flecks:

[attach=1]


The pieces above the rag are proper metal shards:

[attach=2]


There isn’t any obvious evidence that the pan has been off before - except for one strange thing: near one of the mounting holes for the “oil separator plate,” there’s some spiral skip marks which look like someone was trying to drill the hole and allowed the bit to wander off… twice!  I can’t imagine that would have happened at the factory… but why would anyone be waving a loaded drill bit in that direction?

[attach=3]
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on July 01, 2020, 12:04:36 PM
Finally, the oil pan appears to be cracked (hmm... thumbnail upside down again?):

[attach=1]


It’s not, however, in the “usual” spot, around the drain hole.  Plus, no matter how carefully I look, I can’t see any evidence of it on the inside:

[attach=2]


Is it possible that there’s some sort of fracture that doesn’t go clear through?
Title: Re: New (to me!) '77 CB400F - US model
Post by: K2-K6 on July 02, 2020, 09:20:58 AM
The shrapnel looks slightly concerning,  that piece of an arc appears to be heading toward 20/25mm diameter and at a preliminary guess could be something from the gearbox.  Are you continuing to strip motor?

The sump "crack" you could tip it at a slight angle and put petrol into it to above the crack line to see if there's any pathway through it. Generally a crack in casting will pass all the way through it even if pinched tight on opposite face,  I'd suspect it would need attention all things being equal.  Cleaning with a solvent prior to getting it Tig welded would probably be a decent solution,  and leave the weld seam in place,  not ground off.

The sump looks almost as if the bike has been lifted by jack on the sump plug at some point,  not the usual clobbered on the ground that's often seen.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on July 02, 2020, 12:05:36 PM
Thanks K2-K6!

If it matters, the curved piece appears to be more like a 12mm diameter rather than 20-25mm...

[attach=1]

... but to be honest, when examining it closely from all angles, it looks more like a curved shaving rather than a broken piece pre-formed at that arc.  I was not planning to strip the motor at this point, I intended to see how it runs first!

(FWIW, that pile of rubbish looks very much like what came off the oil strainer during my 2011 Royal Enfield's first oil change!  ::) ;D )

I'll leak-test the sump once I get a new plug washer...
Title: Re: New (to me!) '77 CB400F - US model
Post by: paul G on July 02, 2020, 12:22:06 PM
Finally, the oil pan appears to be cracked (hmm... thumbnail upside down again?):

(Attachment Link)


It’s not, however, in the “usual” spot, around the drain hole.  Plus, no matter how carefully I look, I can’t see any evidence of it on the inside:

(Attachment Link)





Is it possible that there’s some sort of fracture that doesn’t go clear through?

I would get that welded up anyway or bin it and get another.
If that goes while you are riding then its a cert the rear Tyre is going to get a coating of its contents :o
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on July 02, 2020, 03:09:01 PM
It could just be a casting flaw
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on July 02, 2020, 03:30:22 PM
It could just be a casting flaw

Have you seen this sort of thing before, Bryan?  If the lack of visible cracking inside the pan isn't convincing, would a "gravity" petrol leak test tell you anything?
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on July 02, 2020, 04:02:30 PM
I see casting marks all the time petrol on inside may show a leak or you could see if anybody local to you in engineering has a dye crack detection kit but if you are real worried can you not get a used one
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on July 02, 2020, 04:07:59 PM
I see casting marks all the time petrol on inside may show a leak or you could see if anybody local to you in engineering has a dye crack detection kit but if you are real worried can you not get a used one

I know some engineering types who may be able to help with leak testing.

I wouldn't say that I'm "worried," since the inside looks fine to me.  I've shopped used ones on Ebay (US), not much there that isn't in worse shape than mine!  I'm actually more worried about the shrapnel that I removed from the sediment in the pan!
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on July 04, 2020, 10:33:20 AM
I almost threw away the washer that fits between the oil filter and the big spring - it was stuck to the filter and I didn't notice it until I was dropping the filter into the recycling bin.

The washer is bent.  How on earth does that happen?  It's sturdy enough that I can't bend it back with bare hands...  (https://advrider.com/f/styles/advrider_smilies/ne_nau.gif)
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on July 04, 2020, 01:04:57 PM
Never seen a bent washer (probably found on workshop floor after being driven over), lost of missing ones yes. The aint expensive to replace.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on July 04, 2020, 01:08:04 PM
Never seen a bent washer (probably found on workshop floor after being driven over), lost of missing ones yes. The aint expensive to replace.

Only very slightly bent... I'll flatten it back out with a hammer - or replace.  Actually, it's probably fine as it is... just surprised to see it.  I guess nothing should surprise me on this bike...
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on July 16, 2020, 03:53:03 PM
Still pondering the possibly cracked sump...

I'm still not sure if the cam chain tensioner action is working, but at least I've found that the external nuts and bolts are free and functional, so that's something.  I know bryanj has described the simple procedure for setting the cam chain tension with the engine off, but is there a simple way of checking the action with the engine not running?  I've photographed the internals through the bottom opening revealed by the sump removal, but I cannot see the tensioner horseshoe or the other parts... I'm not sure it's visible...
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on July 20, 2020, 02:24:01 PM
... is there a simple way of checking the action with the engine not running?

Anyone have any ideas about this?
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on July 20, 2020, 02:34:02 PM
I don't know where this bike was ridden, but the gunge inside the sprocket cover is shocking - chain lube (I assume) flung everywhere, and dirt/sand/grit thickly mixed throughout!  The cover wasn't too bad to clean, as it's removable... but the engine, still on the bike?  What a mess!  Same gunk that was all over the rear of the engine, swing arm, chain guard...

I must admit I'm surprised to see the sprocket mounting splines on the end of the shaft displaying surface rust - everything else is coated with crap, but it's clean and dry (and rusty).  I guess chain lube gets thrown away from the shaft...

Before:

[attach=1]
 

After:

[attach=2]


Piles of crap scraped off:

[attach=3]
Title: Re: New (to me!) '77 CB400F - US model
Post by: K2-K6 on July 20, 2020, 02:52:16 PM
... is there a simple way of checking the action with the engine not running?

Anyone have any ideas about this?

If you uncinch the chain tensioner clamp bolt then put a telltale rod into the shaft hole,  now put the bike in (take out the spark plugs first) gear and turn the rear wheel backwards,  it should visibly push that rod out as the cam chain trys to deflect the tensioner and so rock the horseshoe backwards. 
Then re tension if you turn the engine forward to pull the front chain run tight again, leaving the slack at the rear run for the tensioner to follow suit.
In essence the tensioner rod should go up and down when using opposing direction of crankshaft travel if left unlocked.
Title: Re: New (to me!) '77 CB400F - US model
Post by: K2-K6 on July 20, 2020, 02:58:17 PM
Note;- you've only to turn the crank maybe 10 degree in either direction to see the above and not multiple rotation.

It's just to flip flop the excess play in the chain to front or rear orientation within the two runs inside the cylinder block.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on July 20, 2020, 03:23:30 PM
Thanks K2-K6, that's helpful!
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on July 20, 2020, 06:58:44 PM
I followed your suggestion, K2-K6... there is upward movement of the "telltale" rod when I bump the engine backwards - but not much, maybe just a couple of millimeters... does this sound right?  I don't know how much movement is ideal...
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on August 31, 2020, 02:38:22 AM
I think I'm ready to try and start it up!  Should I use my small auxiliary fuel tank, or better to install the proper tank and use a decent amount of fuel?
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on August 31, 2020, 07:48:53 AM
If you have bench synced the carbs properly fit the big tank and ride it round for the 500 miles till first service then vaccume sync after checking everything else
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on August 31, 2020, 12:01:22 PM
Thanks Bryan!  I did my best to follow your bench-sync instructions - I presume I did it correctly, as the instructions seem very clear and it's not a difficult job.

I haven't done major open-engine work, so I don't think there's a particular 500 mile service to do, but if it runs and seems ok, I'll definitely ride it and keep an eye on things!

What I did do (relevant to engine running):
If it runs, I'll do the usual checks - listen for strange noises (not like I'd know which noises are strange!), check for uniformly heating exhaust pipes, look for smokey exhaust... any other "first-run-after-sitting-for-a-few-years" things to keep an eye out for?
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on August 31, 2020, 12:09:55 PM
I would still do a 500 service as its been sttod and what you have in now will, hopefully, collect any unwanted stuff and put it in filter and/or sump
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on August 31, 2020, 12:11:35 PM
I would still do a 500 service as its been sttod and what you have in now will, hopefully, collect any unwanted stuff and put it in filter and/or sump

Gotcha!

Anything I've missed I should be watching/listening for when I try to run it?
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on September 07, 2020, 10:12:14 PM
A few recent photos - I forgot the mirrors! :-[
Title: Re: New (to me!) '77 CB400F - US model
Post by: taysidedragon on September 07, 2020, 11:34:28 PM
Looking good. 👍
Title: Re: New (to me!) '77 CB400F - US model
Post by: AndyD on September 08, 2020, 09:01:21 AM
Matt,
Bike looks great - hope it runs as well as it looks when you push the button.
 
Cheers,
Andy
Title: Re: New (to me!) '77 CB400F - US model
Post by: Nurse Julie on September 08, 2020, 09:12:54 AM
Nice to see it out in the sun Matt, enjoy.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on September 08, 2020, 01:08:50 PM
Thanks guys!

I took it for a spin around the block, and gradually expanded my range to about a 20 mile ride the other day.  Since using the manual adjusting rig, the cam chain noise didn't get any worse in those 20 miles.  I briefly touched 8K rpms during the ride, no drama.  It does make a public statement spinning up there, though, doesn't it?

It runs pretty well; it doesn't like to start moving in 1st gear with anything less than about 3000 rpm, but maybe that's normal for these small, high-revving engines?  I'm used to my newer daily rider which has plenty of low-end torque.  Plus, while the clutch pull has improved a lot in those 20 miles (getting the plates well-oiled after years?), it's still not what I would call an easy pull, so maybe I'm not able to finesse it the way I should be able to.  But once under way, the throttle seems well adjusted throughout the rpm range.  The throttle grip is also more difficult to turn, and to hold, than I'm used to, but I think that's down to the spring action of four older carbs vs two newer ones.

The brake lever action feels very good.  It just doesn't slow the bike all that well, which I've been told to expect - all four fingers on the lever and a good kick at the rear pedal does a pretty good imitation of a quick stop, but cruising along with two fingers covering the front lever doesn't quite cut it!

I finally got the new shocks sorted, so I hope to get a longer ride in today if the weather holds (looking very cloudy at the moment).  I'll keep an eye out for smoke from the exhaust, of which I saw a little bit at idle during one of my stationary test starts.

You may recall my run of very low - but uniform and consistent - compression tests... the conclusion was that it could be all four chambers were badly compromised - or that my testing tool/method was inaccurate.  I never got any result above 100psi.  If the bike is running reasonably well, does it seem likely that the compression isn't as bad as my test indicated?  What symptoms should I be keeping an eye out for?
Title: Re: New (to me!) '77 CB400F - US model
Post by: taysidedragon on September 08, 2020, 11:42:24 PM
The only obvious sign of low compression would be a lack of power and lower top speed.
From your description it seems to be running ok.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on September 09, 2020, 12:44:12 AM
You, sir, should be asleep!

But... thanks!
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on September 09, 2020, 07:00:49 AM
Add inability ti idle at a normal revs
Title: Re: New (to me!) '77 CB400F - US model
Post by: taysidedragon on September 09, 2020, 10:48:13 AM
You, sir, should be asleep!

But... thanks!

😊 I'm a night owl. Not a morning person! 😉
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on May 05, 2021, 07:54:22 PM
Hi guys - it's been awhile!

I've got the bike out of storage and back on the road... it's where I left it last autumn... starts well, idles well, stumbles mightily when pulling away from a standstill unless I rev it up to 3k-5k rpm as I slowly ease out the clutch... once underway it pulls well through all the gears and normal rev range.  I'm actually quite happy with how it runs... except for that stumbling.

When I cleaned and bench-synched the carbs, I set the pilot screws to two turns out which seems to work well for the most part, other than the above - I followed some advice here and tried screwing the screws in 1/4 turn... which didn't seem to make a difference.  Any other thoughts?
Title: Re: New (to me!) '77 CB400F - US model
Post by: K2-K6 on May 05, 2021, 08:19:54 PM
Set the air screws at 3/4 turn out and try it like that.

Military range finder theory, fire one short, one over the top,  then you know the target is somewhere between the two  :)

Essentially you're trying to find IF it changes and then look at the results to see what it tells you.
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on May 05, 2021, 10:29:10 PM
Set the air screws at 3/4 turn out and try it like that.

Military range finder theory, fire one short, one over the top,  then you know the target is somewhere between the two  :)

Essentially you're trying to find IF it changes and then look at the results to see what it tells you.

Will do, thanks!
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on July 16, 2021, 11:33:39 AM
Well guys - time for a final post to this thread... my CB is moving on.  I never did sort out the stumble off idle - I got lazy about it since once the bike was moving, it ran well.

Once I started putting some miles on it, it didn't take me long to come to pretty much the exact same conclusions as Nurse Julie did - both about her old 400 and her new 500 (I have a larger parallel twin as my daily rider):

I would have to say that riding Hettie was like trying to ride a wasp in a bad mood 😁😁😁😁 Yes, she was very nimble, cornered exceptionally well but, she was very small and light, too small and light for me actually, she was bloody hard work to ride, up and down the gears all the time to keep her revving high but, I absolutely loved riding her because she was such a challenge. The exhaust note was a real scream when riding hard and she was certainly not a lazy riders bike.
Kitty is a totally different ball game, get into 5th gear and she cruises along lovely but, I can overtake a car, or get a move on without even changing down. The handling is superb, very positive around tight bends, the exhaust tone is very 'refined' but sounds fantastic, even when riding quite hard and she obviously revs a lot lower than Hettie. The size and weight is better, although I do prefer the heavier weight of the 750's when riding.
When Kitty is run in fully, I can see I'm going to have great fun on her but in a slightly more sedate way than the fun I had on Hettie.

I live in the middle of nowhere and I know the USA market for these bikes seems to vary wildly between different locales, so I thought I'd take a chance and list it as an auction on Ebay - it's now sold.  Hopefully the next owner will enjoy it for what it is.

Thanks to everyone here who was so helpful during the long period it took me to simply get the bike on the road!  I learned a lot and hopefully contributed something useful occasionally as well...
Title: Re: New (to me!) '77 CB400F - US model
Post by: taysidedragon on July 16, 2021, 03:14:30 PM
Hope to see you back with another flavour of CB. 🏍🙂
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on July 16, 2021, 07:08:35 PM
Hope to see you back with another flavour of CB. 🏍🙂

Thanks Gareth!  Not likely any time soon, but I do still have a large library of photos, notes and wiring diagrams for the 400, so I'll continue to lurk if nobody minds...
Title: Re: New (to me!) '77 CB400F - US model
Post by: Bryanj on July 16, 2021, 09:18:36 PM
of course we don't mind, you may well have an answer from something you've seen that is rare
Title: Re: New (to me!) '77 CB400F - US model
Post by: Laverda Dave on July 18, 2021, 10:28:25 AM
Good luck with your future endeavours.
You could always buy the CB750 you always promised yourself😉
Title: Re: New (to me!) '77 CB400F - US model
Post by: mattsz on July 18, 2021, 10:51:25 AM
Cheers, guys!
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