Author Topic: New (to me!) '77 CB400F - US model  (Read 38196 times)

Offline Nurse Julie

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Re: New (to me!) '77 CB400F - US model
« Reply #15 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 😀😀😀
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Offline Nurse Julie

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Re: New (to me!) '77 CB400F - US model
« Reply #16 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.
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Offline mattsz

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Re: New (to me!) '77 CB400F - US model
« Reply #17 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...

Offline mattsz

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Re: New (to me!) '77 CB400F - US model
« Reply #18 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...

Offline taysidedragon

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Re: New (to me!) '77 CB400F - US model
« Reply #19 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.
Gareth

1977 CB400F
1965 T100SS

Offline mattsz

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Re: New (to me!) '77 CB400F - US model
« Reply #20 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...

Offline SteveD CB500K0

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Re: New (to me!) '77 CB400F - US model
« Reply #21 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.




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Offline K2-K6

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Re: New (to me!) '77 CB400F - US model
« Reply #22 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.

Offline mattsz

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Re: New (to me!) '77 CB400F - US model
« Reply #23 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:




Mine:

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Obviously no good, and behind that kink there's a rip anyway.  Looks like rebuild kits don't include the diaphragm, either...

Offline mattsz

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Re: New (to me!) '77 CB400F - US model
« Reply #24 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:

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

Offline Nurse Julie

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Re: New (to me!) '77 CB400F - US model
« Reply #25 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.
LINK TO MY EBAY PAGE. As many of you know already, I give 10% discount and do post at cost to forum members if you PM me direct.
https://www.ebay.co.uk/sch/julies9731/m.html?item=165142672569&rt=nc&_trksid=p2047675.m3561.l2562

LINK TO MY CB400/4 ENGINE STRIP / ASSESSMENT AND REBUILD...NOW COMPLETE
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Offline K2-K6

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Re: New (to me!) '77 CB400F - US model
« Reply #26 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.

Offline mattsz

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Re: New (to me!) '77 CB400F - US model
« Reply #27 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

Offline mattsz

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Re: New (to me!) '77 CB400F - US model
« Reply #28 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!

Offline mattsz

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Re: New (to me!) '77 CB400F - US model
« Reply #29 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:

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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...
« Last Edit: October 25, 2018, 10:20:34 PM by mattsz »

 

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