Honda-SOHC

SOHC.co.uk Forums => CB750 => Topic started by: Lobo on January 27, 2022, 12:04:53 PM

Title: 750 K2 Strip & Rebuild - help please
Post by: Lobo on January 27, 2022, 12:04:53 PM
Hi all, the big difference to this rebuild thread is that I’ll only write when begging for help as I simply can’t otherwise compete - given the skills of most on here.
So, today broke my  ‘750 K2 down into component parts, for no other reason than I want to, ie pretty the old girl up to how the showroom would have had her in 1973. The engine’s running fine; but I will go through it … tho’ not anticipating any major issues. Menno has kindly painted a body set for me, and all other bits will be plated / finished iaw OEM … as far as possible.
Today’s questions please:
(1) Not mentioned in my manual, but I understand the ‘Connecting Rod’ (ie big end) bolt (& nut I guess) are the yield type .. ie one time use only. Are there ANY OTHER such fasteners in the engine that I should be ordering rather than reusing? I’ll assume the old ones are good for torquing down wrt Plastigauge checks?
(2) I failed to remove the Advance spindle from the RHS of the crankshaft - I bottled out after applying as much force as I was comfortable with. (I was working on the assumption of RH Thread and counter clockwise rotation iaw the American forum btw). So… tips please on ultimately removing this with no tears.
Ta for now.
Title: Re: 750 K2 Strip & Rebuild - answers please
Post by: Nurse Julie on January 27, 2022, 12:15:34 PM
Con rod bolts can easily be used again if not stretched. The manual also states to plastiguage the shells up on the con rod, so what are you supposed to do, fit a new set of bolts everytime you do them up, nah, I think not.
Title: Re: 750 K2 Strip & Rebuild - answers please
Post by: Bryanj on January 27, 2022, 12:44:25 PM
As Julie sez con rod bolts, and in fact no bolts on the 750, are not "stretch" bolts and can be used again
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on January 27, 2022, 08:44:56 PM
Appreciated Julie / Bryan - thanks. Got this ‘duff’ info off a YouTube clip on plastigauging - he called ‘em yield bolts and was adamant one time use only.
Ho hum.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on January 29, 2022, 04:02:57 AM
Crankshaft this time…

1973 Motor, but NOT showing up in my predominantly K0/K1 workshop manual is the bush on the generator side of the camshaft. It looks to me like a mod, with obviously the carrier modified too - comments.

Next up the lobe specs do not tally with those in my manual, the exhaust lobes are more-or-less within spec, but the inlets consistently below spec. The base diameter of all lobes are nothing like book figure…

On a search I found ‘comforting’ news wrt K2+ on the American forum, but again thoughts please.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on January 29, 2022, 04:10:40 AM
And cylinder head now!

Ok, released all 16 nuts in the prescribed manner, and iaw my manual the head did not lift off.

Boll**cks - the single bolt above the tensioner! Ah, and the 4 hidden bolts beneath the rubber plugs - ie shown in Red. (not mentioned in the book.)

The cylinder head still refuses to separate from the cylinder block, and rather than get all physical I’ve decided to walk away for now. The mating area is currently soaking in WD40…

What am I missing here - no give apparent, it’s as though yet more fasteners are awaiting to be released!

Ta.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Trigger on January 29, 2022, 05:27:26 AM
The cam shaft and the cam towers have been modified in the past, due to the oil jets have blocked so, no oil to the cam and it cooked.
There are so many different cam shafts fitted to the 750 and too many different measurements / spec but, as above the cam shaft has been cooked so expect lots of damage to the lobs.

All the bolts are out and it is not usual for the head gasket to be stuck. Heat the head a little but, not too much as the heat can easy damage the valve springs and place a soft length of wood up the barrel sleeve and a good whack with a mallet  ;)

Manuals for these bikes is only good for the fire to keep warm  ::) 
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on January 29, 2022, 11:32:03 AM
Thanks Trig. Got the head & block finally separated - nail biting.

The cam news is disappointing - I’m no engineer but it doesn’t look terribly alarming. I’ve had this CB for 10 yrs now, and it’s never given me pause for thought wrt performance, undue noises, vibration, swarf in the oil etc.

So, I’m at a crossroads - spend £500+ on used parts to correct, or put it all back bearing in mind the bike will only likely do 1000 miles pa.

All thoughts welcome.

(How do the earlier cam carriers differ? Can I fit K0 / K1 / early K2 carriers to a 1973 #2241656 engine? Part # 12010-300-20 / - 30 / -40 … with my bike the -40)
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Bryanj on January 29, 2022, 06:55:39 PM
All carriers will interchange, back in the 70's we used to have a man who re-engineered the journals and made split, pegged bronze bushes. As long as lobes were not blue they always ran ok afterwards
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: philward on January 29, 2022, 09:30:34 PM
All carriers will interchange, back in the 70's we used to have a man who re-engineered the journals and made split, pegged bronze bushes.

Done exactly that on a Phil Read Replica I had
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on January 29, 2022, 11:07:03 PM
Thanks Bryan; that gives me a few more options. (Ie replacement carriers)
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on February 12, 2022, 01:20:49 AM
The strip slowly continues and I note the two Primary chains are differing in ‘slackness’. Is this simply a spendthrift PO trying to save a bob and replacing one chain only… or can there be a more sinister reason? Obviously I’ll be renewing both, but would like to understand the cause…
Ta.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: K2-K6 on February 12, 2022, 12:00:34 PM
Primary seems odd that one would wear more than the other, does suggest they've been swapped (or possibly one) at different intervals.

Anyway, it'll sort out with replacement.  To quantify the wear, wrap the chain fully round the bigger sprocket and pinch together,  then opposite the "join" pull the chain out away from centre to measure mm movement. Then do same with new it'll show just how much it's worn for interest.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on February 13, 2022, 11:29:59 AM
Thanks Nigel - wildo. On the face of it only one chain has been doing all the work I’d guess; lucky the old girl was never thrashed….
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Trigger on February 15, 2022, 10:28:12 PM
Check the rubbers in the primary drive sprocket by holding the center and test how much the teeth move.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on February 16, 2022, 06:55:12 AM
Wildo… thanks Trig.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on March 03, 2022, 09:58:45 PM
There’s been a fair bit of discussion on the forums wrt home plating old nuts and bolts vs commercial plating….
Browsing Yamiya website yesterday, I noted CB750 bolt sets for the body & engine - at a price (and convenience) significantly cheaper than either of the above. (assuming a single bike restoration)

Comments / thoughts pls - on paper it seems the way to go in my case.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Johnny4428 on March 03, 2022, 10:15:15 PM
Seems a good idea as long as the kit contains like for like bolts that are correct for your bike and also would save a lot of fiddly cleaning/buffing. I purchased a general bolt kit from CMS and also cleaned and plated any fittings that were correct for bike and not had the “hairy ape” with the ill-fitting spanner treatment. (I had one or two of them)
The kit did contain the ones that I had to replace so was good. It would be very nice to get a bolt kit that contained washers and nuts IMO.



Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Trigger on March 04, 2022, 06:49:40 AM
The frame bolt kit from Yamiya is for CB750K0, not for a K2 and the engine bolt kit only contains the JIS screws. There are many other nuts bolts and washers that all add up to lot of money, always better to replate the original Honda ones to keep the bike original  ;)
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: AshimotoK0 on March 04, 2022, 08:24:40 AM
I agree with Graham plus the Yamiya 750K0 kit is quite expensive (replicates early  67-69 JIS bolt head markings)  and many of the bolts are not true 'large figure 8' parts. Well that's how they were a few years back .. perhaps they have improved .. James will know  :) Also a lot of Genuine Honda bolts and ones sold by Yamiya  are heavily yellow/gold passivated. If you replate the bolts and  clear/blue passivate them,  then they look more like the original silverey finish with decent weather protection. I don't know when it changed but the bolts used to be cyanide process, zinc plated but are now bright zinc acid plated and passivated.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on March 26, 2022, 11:59:19 AM
Have struck gold in finding a very nearby SOHC Engine guru, who’s been building, modifying, racing the ‘750 unit (sidecars) since 1972.

And extremely generous with his time / knowledge; I traipse up-to his workshop with bits in hand, and rattle through things that would otherwise take me days … if I even knew to do them.

Anyways, yesterday, Lindsay cleaned out the four oil galleries within the crankshaft. (I was convinced this was a waste of time as I’d bathed it 48hrs in degreaser, and then pressure washed those galleries with a garden hose….)

First up he TIG welded blobs of steel onto the ball bearing plugs, before tapping them out with a cold chisel. This gave us access to the gallery downstream of the big end ports…. which were truly blocked with **it. (same workings as a centrifugal oil filter I guess). With a 6mm(?) drill bit this was all removed to a depth of about 1”… ie the bit broke through more-or-less at the big-end oil ports. (The crap that came out was a plastercine like sludge)

Then a wash out, blow dry… replace with a new ball bearing using the original punch marks to secure.

(The top photo shows the gallery path depicted with the screwdriver. The con-rods have been reinstalled and so the big-end oil ports not visible in the pics)

May not impress the established engine builders here - but this was all new to me.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: K2-K6 on March 26, 2022, 12:30:09 PM
"which were truly blocked with **it. (same workings as a centrifugal oil filter I guess). With a 6mm(?) drill bit this was all removed to a depth of about 1”… ie the bit broke through more-or-less at the big-end oil ports. (The crap that came out was a plastercine like sludge)"

The fundamental problem is from oils of that original period being susceptible to tarring at high temperatures. Newer versions of "mineral " oil have improved in this aspect.
The real change though comes from "synthetic" oils that in reality don't do this. I've put those two in " " as the names just don't reveal the full story of how they differ, with most commentators demonising the newer without understanding what they hold prejudices against.
I've used synthetic oils in most engines I look after since the 1980's and principally because that sludge and degradation is not present.

For another thread really though.

Cleaning the oil ways though, I'd use steam to go through these with. Make a nozzle from copper brake pipe or similar, fit to household steamer and blow through anything you can't immediately access.

Sounds a very thorough engine guy you've used there Simon.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: AshimotoK0 on March 26, 2022, 12:40:03 PM
Have struck gold in finding a very nearby SOHC Engine guru, who’s been building, modifying, racing the ‘750 unit (sidecars) since 1972.

And extremely generous with his time / knowledge; I traipse up-to his workshop with bits in hand, and rattle through things that would otherwise take me days … if I even knew to do them.

Anyways, yesterday, Lindsay cleaned out the four oil galleries within the crankshaft. (I was convinced this was a waste of time as I’d bathed it 48hrs in degreaser, and then pressure washed those galleries with a garden hose….)

First up he TIG welded blobs of steel onto the ball bearing plugs, before tapping them out with a cold chisel. This gave us access to the gallery downstream of the big end ports…. which were truly blocked with **it. (same workings as a centrifugal oil filter I guess). With a 6mm(?) drill bit this was all removed to a depth of about 1”… ie the bit broke through more-or-less at the big-end oil ports. (The crap that came out was a plastercine like sludge)

Then a wash out, blow dry… replace with a new ball bearing using the original punch marks to secure.

(The top photo shows the gallery path depicted with the screwdriver. The con-rods have been reinstalled and so the big-end oil ports not visible in the pics)

May not impress the established engine builders here - but this was all new to me.

That's interesting Simon ... probably one of the most interesting posts I have seen on here recently and I wonder what our resident engine Gurus on here think.

It sounds a bit like what mate Graham Curtis does on pressed-together Honda roller bearing cranks. There are inaccessible grooves that clog up with thick highly compacted muck,  that can only be removed by pressing apart the crank and physically removing the compacted debris. He claims that the particles preferentially build up in those internal areas rather than being centrifuged out in the oil filter 'cup' mounted on the end of the crankshaft. Also by removing all of the debris, more oil is flung up into the underside of the piston area (as intended)  and lubricates the small end better.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: K2-K6 on March 26, 2022, 02:35:13 PM
Ash, it's mirrored in any specific site within engines that take the oil above critical temperature limits.  Probably in the range of exceeding 155 / 175 C for localised conditions.  This will often be propogated when the oil becomes stationary after turning the engine off and the heat can no longer be extracted by continuous oil flow.

Ultimately, in these small passages it gives compromise to the desired flow as carbon builds, then making it even more susceptible to over heat.

Generally the oil is targeted to run at 90C continuous,  and would largely be out of range for mineral oils above about 135C.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Oddjob on March 26, 2022, 03:27:15 PM
Your wrong Simon, that impressed me. Never heard of anyone doing that before, great info and might explain those unexplained "why has my engine seized" questions when there is no rational explanation, a big clump of that stuff coming loose would ruin most engines, who knows what it contains.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: AshimotoK0 on March 26, 2022, 03:59:50 PM
Your wrong Simon, that impressed me. Never heard of anyone doing that before, great info and might explain those unexplained "why has my engine seized" questions when there is no rational explanation, a big clump of that stuff coming loose would ruin most engines, who knows what it contains.

Impressed me too .. I had always wondered about those sealing balls but thought removal would be a nightmare and since I never heard of anyone removing them and finding what lies underneath them I kind of (probably wrongly) dismissed the idea. I have a decent TIG welder and a scrap crank so going to try it out sometime ... although my scrap crank is a very early die-cast and I seem to remember that that they may be sealed differently. How easy was it to chisel the balls out Simon, that's assuming you were there when he did it. I wonder what Vic World does or possibly sandcast cranks don't have those balls ?
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: taysidedragon on March 26, 2022, 04:39:42 PM
Yes, very thorough.  He obviously knows his stuff.
Old Triumphs have a designed sludge trap in the crank which has to be cleaned out occasionally, along with the oilways.  It can be difficult to access but not as difficult as removing those ball bearings.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: AshimotoK0 on March 26, 2022, 05:28:59 PM
I found this post on the USA site regarding the sealing balls

http://forums.sohc4.net/index.php/topic,146287.msg1664725.html#msg1664725
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Trigger on March 26, 2022, 06:31:38 PM
You should always remove the balls when cleaning a crank. The later 750 crank has grub screws with are easier to remove  ;)
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Oddjob on March 26, 2022, 09:24:22 PM
I have 2 scrap cranks I was going to give to the scrapman but I might have a go at getting those ball bearings out for a laugh.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on March 26, 2022, 09:26:43 PM
Whilst I was there a couple of cranks were done Ash, the first whose balls were rather proud 🥹, and mine whose were relatively recessed. The 1st crank, well, they popped out at first strike of the cold chisel, and on mine a couple+ of strikes were necessary, with one re-TIG’ing of a blob - the outcome tho’ was never in doubt.
Be sure to have replacement balls….

Lindsay mentioned the latter grub screws, and also that on any ball-plugged cranks intended for racing he’d tend to modify them to this.

Nige, many discussions wrt Synthetic oils…. do I assume you use it in your SOHCs with no detriment to the clutch? And if so are you increasing the change times?
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: AshimotoK0 on March 27, 2022, 12:50:49 PM
You should always remove the balls when cleaning a crank. The later 750 crank has grub screws with are easier to remove  ;)
  What's your recommended method for removing the balls Graham?
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Trigger on March 27, 2022, 06:49:32 PM
You should always remove the balls when cleaning a crank. The later 750 crank has grub screws with are easier to remove  ;)
  What's your recommended method for removing the balls Graham?

Crank in a big vice, lay a penny washer over the ball, weld a rod to the ball, attach the slide hammer to the rod and pull out  ;) Never tried a chisel before.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: K2-K6 on March 28, 2022, 09:02:33 AM
Nige, many discussions wrt Synthetic oils…. do I assume you use it in your SOHCs with no detriment to the clutch? And if so are you increasing the change times?
yes to using it in sohc engines without clutch problem.

It's as you mention a contentious subject. Routinely I've never ever worn a clutch out on bike or car, and so may have a different view from others. Aware that routinely some riders/drivers get nothing near the clutch life I experience, so a caveat there to start with.

I've looked after bikes that the rider habitually trashed the clutch with not any input from synthetic oil.

It could be turned the other way round for arguement sake. Given the choice of assessment to see if your bike has clutch slip if you use this type of oil, a potential only, to are they willing to compromise the bearings etc from poor oil conditions, which would they rather replace ? Clutch or engine rebuild ?

Many comments about clutch slip come from completely unqualified views. There's many different influences as to how a clutch can slip, but their projection only sees "slippery" oil.
One of the determinants here is that most are completely unaware that synthetic engine oils aren't more slippery than mineral type. It's just a non informed assumption. 
The facts here are (even in your own engine) there's been lubrication failure, however that occurred, that compromised the cam in it's history. Also that it has evidence of sludging in the crank passageways.  Far from perfect in any unbiased view. These engines, with decent lubrication should easily see 100, 000 miles, in pure engineering materials terms, why many of them don't is more the question I'd ask.
As you mention Simon, it's a densely packed topic and often filled with hearsay along with little phrases used in place of good technical explanation.

Perhaps a dedicated thread worthwhile.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Trigger on March 28, 2022, 09:22:53 AM
Every customer i have had in with clutch slip problems is that they are still using the old 40 year + plates or a high grade of synthetic oil.
Having gone by the Manual and measured the thickness of the plate and it is within spec. They have not taken in to that the friction plate has gone hard over time and is just slipping due to a hard surface and always say, but it is within spec  ;) 
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: K2-K6 on March 28, 2022, 10:12:51 AM
The collective noun used by oil manufacturers is "lubricity" in description of how slippery an oil or fuel is. Covering a multitude of properties including shear stability, absolute shear strength etc.

It's very hard to form a competent position that can clearly attribute better lubricity to synthetic oil over and above a mineral oil. In other words they don't really differ much, if at all. It's the assumption that synthetic is more slippery that undermines most arguments against using synthetic.

The properties it has that are capable of outperforming mineral are in flow characteristics/viscosity range (high VI range) oxidation stabilisation,  raised heat tolerances,  all of which are a valuable asset in this situation. 
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Bryanj on March 28, 2022, 11:20:22 AM
I think one of the problems is people see synthetic but think friction modifiers which early synthetic car oils had as well and its those that cause clutch slip
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Oddjob on March 28, 2022, 02:36:29 PM
Getting those ball bearings out isn't for the faint hearted I'd imagine. Much better to have a spray that can dissolve the sludge without having to resort to drilling it out. Maybe someone like Ash can get some of the typical muck left in this passage and see if he can find a fluid which readily dissolves it, brake cleaner seems to work for instance but doesn't by all accounts do it totally. Knowing Ash he'll invent some exotic cocktail that will solve the problem without having to remove the ball bearing and potentially ruin a good crank.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on March 28, 2022, 10:47:02 PM
Surely the problem Ken, is that you’re unable to directly point any spray at the column of sludge given the geography of the holes. So (useful) mechanical degreasing / washing out is off the cards. Next issue is the 6(?) mm column, 1” high (?) of compacted ‘plastercine’ - how are you ever going to know it’s all dissolved?
Could ultrasonics be used? - though I guess the mass of the crankshaft would negate that?
The (grinding) method of removing the balls Ash put out on his link would be easy enough for most DIYers - given they had enough nous to get the CS out in the first place?
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Oddjob on March 29, 2022, 12:26:56 AM
Odd thing is that the 500/550 crank only seems to have 2 ball bearings at each end, so how were the inner rods lubricated?

Didn’t someone post they’d sprayed brake cleaner down the holes from the conrod pin?
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on March 29, 2022, 04:27:49 AM
Slight change of topic here, but with the bike totally stripped it might be time to swap the front brake from DOT 3 to Silicon fluid. If I plan to keep the existing master, hoses, caliper etc can someone pls advise me which is the best cleaning fluid to use on these components.
(Braced for…. ‘Brake cleaner’! 😂)
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Trigger on March 29, 2022, 06:51:42 AM
I changed all my bikes to oke dot 5 silicon. You have to strip the M/C and the caliper completely and clean out with clutch and brake cleaner. It is only a hours work  ;)

It is the worst thing to do is soak a crank in anything, this will just loosen the crap and you not be sure if you have it all out. Do the job once and do it right  :o
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on March 29, 2022, 08:01:51 AM
Cheers Trig, wildo.

Next cleaning job are the clutch plates which @ 3.5mm thickness are good. Plan to immerse them in petrol overnight followed by same in a strong non-corrosive degreaser - will this be inviting trouble?

Ta.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Trigger on March 29, 2022, 12:32:05 PM
Cheers Trig, wildo.

Next cleaning job are the clutch plates which @ 3.5mm thickness are good. Plan to immerse them in petrol overnight followed by same in a strong non-corrosive degreaser - will this be inviting trouble?

Ta.

NOT petrol, it will loosen the fibers off the plate. Used Clutch and Brake cleaner  ;)
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: K2-K6 on March 29, 2022, 04:44:18 PM
Surely the problem Ken, is that you’re unable to directly point any spray at the column of sludge given the geography of the holes. So (useful) mechanical degreasing / washing out is off the cards. Next issue is the 6(?) mm column, 1” high (?) of compacted ‘plastercine’ - how are you ever going to know it’s all dissolved?
Could ultrasonics be used? - though I guess the mass of the crankshaft would negate that?
The (grinding) method of removing the balls Ash put out on his link would be easy enough for most DIYers - given they had enough nous to get the CS out in the first place?

Important I feel to make the distinction here about how the "sludge" gets there. It's not travelling in the oil as sludge (it would be trapped by the filter if that was the case and prior to delivery) it's symptomatic of the oil used passing over temperature threshold at that specific site/location that causes it to bake out the components that stick to the metal. Think more of baked on oil in a domestic oven.
It can only do this by becoming stationary (or close to it) at a site that's above the critical temperature, and one of the important limitations of this oil type. Most likely when crank is stationary after running that has internal structure at elevated temperature, along with the oil sitting there. Essentially you can't cure it with this oil, the risk will always be there. Other less heat intensive sites have an absence of this effect.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: AshimotoK0 on March 29, 2022, 04:54:21 PM
I've talked with a few guys whose opinion I really rate and have hundreds of thousands of miles on Honda 4 engines under their belts. I still think the jury's out on this one but my gut feeling now I know the debris is probably in there but well compacted it to ideally clean it out by removing the balls (or screwed in but still staked plugs on early cranks). However I agree that if you are not going to do that then dont mess and try to soften the debris as you may soften but not remove it ..only for it to become dislodged when you run  the engin It's a pity we dont have any close up photos of the peened area post removal of the balls and also some idea of how much force it takes to pull the balls out. Nevertheless, I think I will have a go with my 750 crank simply because I have no idea of its history , other than Bryan kindly sold me it yonks ago and I think it came from a batch of engines he had....In terms of wear it's very nice though.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: K2-K6 on March 29, 2022, 05:37:31 PM
I don't think you can dissolve carbon Ash, is that true in chemistry?  Only mechanical means I've been aware of. It's essentially, the soft element grease with carbon black in it as far as logic determines.

Ordinarily something like oven cleaner, sodium hydroxide should dissolve the "fats" to release the debris and flow it out. Also in chemistry labs steam is used to remove tarring from glassware, vessels etc. Small bore probe attached to a wallpaper stripper could be used. Maybe, in the interest of science, it'll be worth steaming one or two before then removing the balls to gauge effectiveness of method Ash.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Oddjob on March 29, 2022, 08:01:38 PM
Well I've managed to remove the ball bearing out of a 500 crank. I'll be really honest here and say I do think this is a storm in a teacup. First off, the buildup is a grey powder, this is on a crank that's sat outside in the rain and such for some years and the buildup was still bone dry. The powder smells exactly like old burnt oil, it's just got that distinctive smell that we all recognise. The hole is 6mm and the buildup was quite solid, I didn't drill it out as that's wouldn't show how deep the powder was, so I used a small straight pick and essentially just pushed it in and turned at the same time. The powder was approx 1" deep, the gallery was completely free of powder after that. So I think what happens is that old oil collects in this pocket below the ball bearing, over time as Nigel has explained due to heat and such it just dissolves leaving the polymers, strands etc behind, this keeps collecting and is compacted due no doubt to the rotation of the crank throwing it together. However it only forms I think because this pocket is a dead end, below the journal the oil doesn't collect so it doesn't dry out and form this powder.

In short I think the powder isn't really a problem, ok if you've got the equipment yeah you can remove it but it's not going anywhere IMO. The powder is extremely fine and doesn't seem abrasive at all.

So let's hear your thoughts on this opinion.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on March 29, 2022, 10:36:26 PM
You’re possibly right Ken; I’d submerged my whole crank in a degreaser for 24 hrs - which may be the reason its collection was a paste versus powder. On the other hand, it was an active crank versus a log-time unused… could this be the issue? Given a crank normally lives in a very wet & oily environment how could a dry powder result?
Notably the remnant sludge (ex drill extraction) dissolved easily with multiple squirts of degreaser down the hole - going to almost a grey thick ink. (The crank / holes were then power washed using a high pressure hose, with compressed air blown finally blown through the galleries. You’ll forgive me Nige not suggesting Lindsay that I take it home to steam it through 😂!)
Ash, yea sorry wrt pics. Certainly not much force needed striking the balls out with the cold chisel… I’d describe it as a ‘middling’ strike. But, there was no visible damage to the holes and the new balls had to be lightly punched back in before the OEM peening holes were used a second time buttoning it all up.
The reason the buildup was in there was described due centrifugal forces, ie any small crap migrating there / into the blind alley.
As a final comment to your post Oddjob, if Honda agreed the buildup was of no consequence to the longevity of the big-ends why would they go to the additional expense of modifying the balls to grub screws?
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Oddjob on March 29, 2022, 10:51:52 PM
Who knows why Honda did things. It could be for safety reasons, maybe one of the ball bearings let go and they decided to modify it to stop that in future. You've got to admit it's a cowboy way of doing things, punch holing a ball bearing in order to keep it in place, maybe there was oil leaking past and reducing oil pressure. TBH we'll never know why they changed it, don't forget they probably didn't make the cranks, they'd have sub contracted them out, maybe they specified a grub screw instead of the ball bearing and there was no additional expense for them but for the sub contractor.

As for the paste versus powder, maybe we need another source for comparison, either way I don't think it would ever shift as there is no flow past it to cause it too move. Plus, and think about this. The oil trapped there was already filtered as it had already passed through the filter, so what exactly is the sludge/powder but dried up oil, as I said it felt non abrasive, so if it did let go and move what would if affect and where would it go, it should just dissolve into the new oil and get filtered out by the filter as it passed through. IF it felt abrasive, and I'm not saying it couldn't be, I'd be saying for gods sake remove it before it does let go. However IMO the potential for damage doesn't warrant the effort to remove it.

Just my opinion of course but I won't be doing my crank and that's done MAJOR mileage, well over 100000 miles.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Bryanj on March 30, 2022, 12:06:58 AM
Having done more than a few Triumphs, their sludge trap gets quite full and does restrict oil flow BUT they have no filter and the trap is in line with big end pins so gets max centrifugal force. The Honda is on a blind line so theory says it will only be a problem if there is so much it fills that line.
On an asside Fiat used small core plugs to block the oilways, i rebuilt one that had knocked an end where the plug had fallen out!
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: K2-K6 on March 30, 2022, 09:03:10 AM
The "Ash" content results from sulphated ash (phosphorus and sulphur) that's part of these original mineral oils and shows the oil has gone over temperature at that location. It's not abrasive, so low risk from that. This is what low SAPS oils are about now, if the oil gets into the combustion chamber it burns (over temperature same as this crank site) and forms ash which is detrimental to exhaust cleaning equipment. 
The older engine types use these components in combination with their metallurgical makeup to help stop wear.

The sludging is only from oil going over it's critical temperature AT THAT SPECIFIC LOCATION because the component is too hot if the oil there becomes slow moving. It's also seen in turbo bearings (hence the addvice to keep running a turbocharged motor after extreme heat to prevent the oil becoming stationary. Also other strategies are now more common with flow pumps after switching off and watercooled casings etc, this to prevent localised sludging. Often seen on Rover V8 in rocker cavity as the aluminium skull caps over combustion chamber eject a lot of heat that way and particularly above the exhaust ports. Notice how Honda put airflow passages throughout the head to control that effect on these sohc engines. 

I'd view the ball bearings as more gentle solution than threads to block the holes. Threads always carry more risk of propagating cracks from their form rather than a peaned ball arrangement.

I should be considered that the potential blocking with sludge can be serious in terms of oil distribution.  If the crank pathways impede the volume of oil in any significant way the pump when meeting this resistance can blow the pressure relief valve open (this is to save it's own drive mechanism from potential hydraulic locking of oil pathway) too much of this can obviously starve the crankshaft and bearings, but just as serious is the interaction of the pressure check "jets" going to the head. These must be capable of containing 60psi as that's what they do in separating the pressurized crank from the open bath camshaft area. If the oil pump pressure relief opens, it's likely that no oil will be pushed into the head while that's happening.  It'll also be worse when cold as the oil is thicker. Part of rebuilding would sensibly cover this off surely?
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: AshimotoK0 on March 30, 2022, 10:26:56 AM
I just had a quick look in Hondman's book on the CB750 and couldn't see any mention of removing balls/plugs or  internal cleaning of the crankshaft ... surprised really and it's a very in depth book.
Unless I have missed it of course  :-[
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Oddjob on March 30, 2022, 03:31:15 PM

I'd view the ball bearings as more gentle solution than threads to block the holes. Threads always carry more risk of propagating cracks from their form rather than a peaned ball arrangement.

I should be considered that the potential blocking with sludge can be serious in terms of oil distribution.  If the crank pathways impede the volume of oil in any significant way the pump when meeting this resistance can blow the pressure relief valve open (this is to save it's own drive mechanism from potential hydraulic locking of oil pathway) too much of this can obviously starve the crankshaft and bearings, but just as serious is the interaction of the pressure check "jets" going to the head. These must be capable of containing 60psi as that's what they do in separating the pressurized crank from the open bath camshaft area. If the oil pump pressure relief opens, it's likely that no oil will be pushed into the head while that's happening.  It'll also be worse when cold as the oil is thicker. Part of rebuilding would sensibly cover this off surely?

I'd agree with the blocking comment IF the part being blocked was in use, the area in question is a dead end or blind gallery as Bryan puts it, no oil passes through it. As soon as this area filled after the first fire up of the engine it most likely stayed there, it's ability to drain is severely compromised by the way the shells are made, conrods shells do not have the recess in them like crank shells so they'd effectively block the gallery as soon as the engine stops, when the engines running the oil pressure would be the thing pushing the oil through the very small gap between the shell and the crank journal, I suspect the oil is far too thick even when hot to get through the same gap without pressure. That's my opinion anyway. My findings were that below the blind gallery the oilways were free of all powder/sludge. When I ran a drill down them it came back clean except for the occasional sliver of metal where it caught the side of the gallery.

As for the peened ball question, surely that can't be oil tight, the very act of peening would distort the area around the ball causing small openings, maybe the fact they are quickly blocked by the sludge/powder is a good thing otherwise you'd surely have some loss of pressure. You wouldn't get that with threads especially with thread lock used.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on March 31, 2022, 08:58:21 AM
Aren't carb galleries regularly plugged with peened balls? And if so, you’d have to assume the method as good engineering practice in terms of high performance / reliable sealing.

As a fan of ‘simple is best’ (been a LONG learning process that one 😂) I got to say I quite like the elegance of it all ….
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: K2-K6 on March 31, 2022, 11:43:04 AM
Haven't looked in detail at them, but peaning will easily do this.

Regarding method though, ideally it would involve peaning round the ball in one operation.

Imagine a ball bearing that's larger than the one used in the hole, with a hole bored in itself, placed over the crank and ball assembly, then when you thump it (technical term for lumping it one  ;D ) it's own surface will compress the ring around the installed ball to pean the surrounding material in place to hold the ball and make it oil tight.

It's basic riveting really,  but with a different "snap" set to give the required metal displacement.  This stuff is pretty routine on steam boilers etc, implemented properly been holding stuff together since the industrial revolution  ;D

Guess you could call it "angular riveting" and that would certainly make your eyes water  :o

Ballls actually seal really easily,  another example is 1/4 turn ball valve in plumbing.

The issue with threads is that it cuts into the structure and makes a stress raiser all round the pointy section. Why you're unlikely to see threads cut into conrods etc.
Honda obviously okayed that though on the late cranks from observations further back.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: K2-K6 on March 31, 2022, 11:59:59 AM

[attachimg=1]

That one on the right hand side looks like the arrangement you'd need. It can't touch the ball though as you don't want to push that inwards just set the material uniformly around the ball to enclose it.

Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Oddjob on March 31, 2022, 03:24:56 PM
The cranks though Nigel are peened using 3 strike areas, well it is on the 500 crank. Seems they just used a centre punch.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Trigger on March 31, 2022, 03:28:34 PM
You just use a center punch at 3 points  ;)
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: K2-K6 on March 31, 2022, 03:52:49 PM
 :) no wonder they don't mind threading them then.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: taysidedragon on March 31, 2022, 04:14:55 PM
You just use a center punch at 3 points  ;)

Are the balls a slight interference fit, so they seal when tapped in to place. The peening just stops them being vibrated or pushed out?
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Trigger on March 31, 2022, 04:31:27 PM
You just use a center punch at 3 points  ;)

Are the balls a slight interference fit, so they seal when tapped in to place. The peening just stops them being vibrated or pushed out?

Tell me something i don't know, and i don't want to know what you had for breakfast  ;D ;D ;D
Once out it, is always good practice to replace them with grub screws and do not run the tap all the way though, only to the seating ledge  ;)
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on March 31, 2022, 09:38:51 PM
…Nige, page #2 of this thread has a pic of the 3 punch marks. Patently done on a Monday morning after a heavy weekend on the saki….
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: K2-K6 on March 31, 2022, 10:00:30 PM
Yes simon  I saw that and thought it was perhaps done later.  As you say maybe a Monday morning after heavy weekend.

It's more me with an aversion to stress raisers I suppose. Original background training during which if we were just paranoid about potential stress point,  then could be considered a bit of a lightweight in engineering terms  ;D

Point holes like that, thread peaks in stressed structures, no radius in tight machined corners all give the hee-b-gee-bees in stress terms.

Guess as a production item Honda specified the crank with plenty of meat on it to make it reliable. 

I've seen them closed in the way I describe, but can't immediately remember which crank it was.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on April 01, 2022, 11:53:30 PM
Yup, stress / fatigue in engineering more and more to the fore. My bil been very involved with live data vibration monitoring in helicopters - big business now. You have to wonder how the early Comets made it through to production - surely someone might have observed, “er, that radius looks a little tight given the fuselage will be pumped up & down like a balloon over its life….”  An interesting story that one.

I digress. Ok, a bit nerdy this one, my engine refurb has morphed into the whole bloody bike. Anyways, the Clutch and brake levers. Was the clear plastic covering intended to be taken off in the pdi. And if not, why is it there? Was it on both levers? Notably the DSS / Yamiya OEM offerings don’t appear to incorporate it.  (I ask because I intend to trial clear heat-shrink over the levers. My mint sandcast, which has been my go-to, has it only on one lever…. it seems I may have to return it 😂)

Ta.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: taysidedragon on April 02, 2022, 01:08:15 AM
Yup, stress / fatigue in engineering more and more to the fore. My bil been very involved with live data vibration monitoring in helicopters - big business now. You have to wonder how the early Comets made it through to production - surely someone might have observed, “er, that radius looks a little tight given the fuselage will be pumped up & down like a balloon over its life….”  An interesting story that one.

I digress. Ok, a bit nerdy this one, my engine refurb has morphed into the whole bloody bike. Anyways, the Clutch and brake levers. Was the clear plastic covering intended to be taken off in the pdi. And if not, why is it there? Was it on both levers? Notably the DSS / Yamiya OEM offerings don’t appear to incorporate it.  (I ask because I intend to trial clear heat-shrink over the levers. My mint sandcast, which has been my go-to, has it only on one lever…. it seems I may have to return it 😂)

Ta.

The Comet story is an interesting one. Being the first jet airliner in service and pressurised, flying at higher speeds and altitudes, it met with different problems never encountered before.
Unfortunately,  they learnt the hard way that square windows and metal fatigue don't work. The redesigned Comet had oval windows.
The test tank they used at Farnborough to discover the problem was still there on the airfield well into the Eighties,  I got a guided tour of it in the Seventies when my uncle worked there, it's maybe still there?
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: K2-K6 on April 02, 2022, 10:25:59 AM
The lever's coating appeared to have been dipped originally (from memory) as the pivot end looked like a thick paint that had dried in a tapered type ending.

Most bikes appeared to have it left on going to customer.

There was a coating we used at Farnborough years ago, called Vi-cote and seemed like a spray on  clear pvc, but can't trace anything of it now. Perhaps safety has done for it as it was in aerosol can to spray with.

Found this https://starscenic.net/ronan-vinyl-cote-uv-clear.html and wondering if it's anything like that product. 
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: AshimotoK0 on April 02, 2022, 10:37:38 AM
The lever's coating appeared to have been dipped originally (from memory) as the pivot end looked like a thick paint that had dried in a tapered type ending.

Most bikes appeared to have it left on going to customer.

There was a coating we used at Farnborough years ago, called Vi-cote and seemed like a spray on  clear pvc, but can't trace anything of it now. Perhaps safety has done for it as it was in aerosol can to spray with.

Found this https://starscenic.net/ronan-vinyl-cote-uv-clear.html and wondering if it's anything like that product.

I used some ultra clear  heatshrink .. special stuff from RS Components. You chop a bit off and slot it onto the lever and then put in a pre-heated oven at 160 deg C (fan)  for a couple of minutes. Agreed original was probably a dip coat. Send some of this to a few people I rate for doing top restos and they thought it was a good solution. Will dig out the RS partno. Ordinary cheapo clear heatshink give a poor result.

https://uk.rs-online.com/web/p/heat-shrink-tubing/7004462


Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on April 02, 2022, 12:48:02 PM
…thanks gents.
Did try a ‘standard’ heat shrink today - not esp impressed. Will soldier on - thanks Ash for the link.

Still unsure what the purpose was…
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: K2-K6 on April 02, 2022, 01:51:11 PM
Purpose, speculative that it's a relatively low cost way of giving protection to a high wear surface. Most polished surface (that from operation) leaves the alloy easily attacked by road salt, making a poor appearance over time.

Later type with black anodized finish (eatly 80s) appear to do the same thing, still get very polished in use but don't seem to succumb to corrosion. 

Presumably the original plastic coat was to preserve how the bike aged at reasonable cost in manufacturing.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Trigger on April 02, 2022, 02:02:58 PM
…thanks gents.
Did try a ‘standard’ heat shrink today - not esp impressed. Will soldier on - thanks Ash for the link.

Still unsure what the purpose was…

That wrap is tooo short. Here is a picture of an original.

[attachimg=1]
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Oddjob on April 02, 2022, 02:06:13 PM
Never thought of why they put it on before but could be for grip, alloy can be slippery and maybe the plastic is grippier.

Saying that I removed mine and had the levers chromed, can't say I noticed any difference.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on April 02, 2022, 10:20:32 PM
Thanks Trig. Little secret - all I had in my electrical box was 80mm of clear! (Trial run) But the measurement appreciated.
I’d have to say it doesn’t look dipped?

Simon
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Trigger on April 02, 2022, 11:03:33 PM
Thanks Trig. Little secret - all I had in my electrical box was 80mm of clear! (Trial run) But the measurement appreciated.
I’d have to say it doesn’t look dipped?

Simon

Yes, the original was dipped to get the cover on and then dipped again for the plastic ball cover  ;)
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Oddjob on April 03, 2022, 02:53:16 AM
Ball cover is not dipped, it’s available as a spare, I fitted them to my chromed levers to make them look original.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Trigger on April 03, 2022, 08:37:15 AM
Ball cover is not dipped, it’s available as a spare, I fitted them to my chromed levers to make them look original.

I thought you was an expert on SOHC's. The original lever P/N 53190-286-670 came with a plastic ball cover  that had to be dipped on and the replacement cover 53180-286-000 is rubber. They could not do a replacement in plastic as, you would never be able to fit it  ;)
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on April 03, 2022, 11:48:20 AM
Trig…. Am I reading this wrong as the end (rubber?) cap does indeed appear to be a stand alone part #. (Ie #12, part no 53180-286-000)
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on April 03, 2022, 11:55:49 AM
Folks - the Throttle Grip Adjust bolt…. part # 11 below.

At fully screwed in, mine makes no difference, suggesting to me a friction piece is missing between the shaft of the adjust bolt, and the twist grip cable guide.

Any clues as to its shape - I’ve now taken the internal measurements to fabricate one up, but before I start just wondering whether it’s a a simple ‘cap’ atop the bolt shaft.

Appreciate the dangers of such a mod going walkabout in the twist grip area at 70mph 🙄.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Oddjob on April 03, 2022, 02:38:36 PM
The sleeper ramp as I call it regularly falls out when the switch is removed from the bars, you don't tend to notice and if you find it lying loose on the garage floor days later you wonder what the hell it is. It's really a consequence of it being greased up by the factory that it falls out so easily. It's a weird shape, I have quite a few NOS lying around, genuine Honda not repros, I'll see if I can take a pic. In essence they are like a tank track with the middle dipping inward on the upper edge, not sure if it does that same on the bottom but probably, just off memory here.

As for the ball covering, yes they are rubber and they aren't exactly easy to fit either. Maybe the supplier originally dipped the lever ends but Honda found they were easily damaged and had replacements made in rubber as a result. Not economical to replace the entire lever for a small scratch in the lever end, hence the replacement. Your statement saying they were dipped was misleading as it inferred they couldn't really be replaced, which as we now know isn't exactly correct.

I've never claimed to be an expert on SOHCs Graham, the signature may say that but that's not something I've put on there, I dislike 750s for instance so I never really bothered to learn that much about them, 350 fours I know very little as they weren't really imported into the UK, 400 fours I don't mind, did quite a few back in the day but my favourite SOHC was and always will be the 500 four. I know a great deal about them as they interest me, hence knowing that the ball lever covering was available as a spare part. I'd appreciate the constant sniping of my comments you've been doing lately would stop, just because I started to sell camchains to members on here and in your words "was taking food out of my mouth" you've had a bag on ever since. I appreciate your not well and that's why I've not really said anything before but if you want to start slinging dirt that's fine but be prepared to get muddy as well.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Bryanj on April 03, 2022, 03:06:03 PM
Its part number 9 in that diagram
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on April 03, 2022, 09:14:50 PM
Well blow me! Thanks Bryan, I’d have never guessed - looks nothing like I was expecting.

Cheers Ken - appreciated.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Oddjob on April 03, 2022, 09:50:34 PM
You still need a pic Lobo? Happy to oblige if you do. Shame your in Oz or I'd have sold you one. It needs to be a sort of spring metal, any other will distort I reckon.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Trigger on April 03, 2022, 11:14:24 PM
The sleeper ramp as I call it regularly falls out when the switch is removed from the bars, you don't tend to notice and if you find it lying loose on the garage floor days later you wonder what the hell it is. It's really a consequence of it being greased up by the factory that it falls out so easily. It's a weird shape, I have quite a few NOS lying around, genuine Honda not repros, I'll see if I can take a pic. In essence they are like a tank track with the middle dipping inward on the upper edge, not sure if it does that same on the bottom but probably, just off memory here.

As for the ball covering, yes they are rubber and they aren't exactly easy to fit either. Maybe the supplier originally dipped the lever ends but Honda found they were easily damaged and had replacements made in rubber as a result. Not economical to replace the entire lever for a small scratch in the lever end, hence the replacement. Your statement saying they were dipped was misleading as it inferred they couldn't really be replaced, which as we now know isn't exactly correct.

I've never claimed to be an expert on SOHCs Graham, the signature may say that but that's not something I've put on there, I dislike 750s for instance so I never really bothered to learn that much about them, 350 fours I know very little as they weren't really imported into the UK, 400 fours I don't mind, did quite a few back in the day but my favourite SOHC was and always will be the 500 four. I know a great deal about them as they interest me, hence knowing that the ball lever covering was available as a spare part. I'd appreciate the constant sniping of my comments you've been doing lately would stop, just because I started to sell camchains to members on here and in your words "was taking food out of my mouth" you've had a bag on ever since. I appreciate your not well and that's why I've not really said anything before but if you want to start slinging dirt that's fine but be prepared to get muddy as well.

It was not a sniping at you. I was just putting you straight on your comment which was wrong information, that the ball cover was not dipped. When the original levers came with a plastic ball cover and not rubber on a original lever. I hate wrong information given out and i will correct any incorrect information given by any member  ;)
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Trigger on April 03, 2022, 11:19:07 PM
Folks - the Throttle Grip Adjust bolt…. part # 11 below.

At fully screwed in, mine makes no difference, suggesting to me a friction piece is missing between the shaft of the adjust bolt, and the twist grip cable guide.

Any clues as to its shape - I’ve now taken the internal measurements to fabricate one up, but before I start just wondering whether it’s a a simple ‘cap’ atop the bolt shaft.

Appreciate the dangers of such a mod going walkabout in the twist grip area at 70mph 🙄.

I have a few of those floating about somewhere. You can still buy them as a Kit >>> https://www.yamiya750.com/index.php?main_page=product_info&cPath=246_251_144_70&products_id=753

If i find one i will post a picture for you up against a ruler  ;)
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Trigger on April 04, 2022, 12:12:37 AM
I found two in the end. I have never fitted one to a bike but, when i sell a bike i always give them to the new owner. And the metal they are made from is magnetic  ;)

[attachimg=1]

[attachimg=2]

[attachimg=3]
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on April 04, 2022, 11:30:06 AM
Thanks gents….. really appreciate the help.

Amazingly, once Bryan had pointed it out as part 9, I typed the Honda part # into eBay and one came up - here in Oz! Not cheap at £15 inc postage, but on balance I’d rather pay that rather than fabricating the part given the pain of where it resides in the handlebars.
Result.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on April 04, 2022, 11:40:20 AM
One for the alchemists….. Ash!

1/4 of the Airbox to Carb manifolds has mummified around 25% of the belmouth, ie the portion within the ‘box. The rest of it, and it’s siblings, are brand new pliable - which they should be as only a couple of years old. Heat makes it pliable, but on cooling we’re back to square 1.

Asking for Wintergreen draws stares here - unheard of. I can find some on eBay… but at a price.  So… does this mix of WG + alcohol (Isopropyl) REALLY work… or should I just spend the $$$ on a new set. (not cheap ☹️)

Notably these manifolds are not actually rubber (?) - and more of a shiny neoprene (?)

Ta again.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Oddjob on April 04, 2022, 03:38:06 PM
The sleeper ramp as I call it regularly falls out when the switch is removed from the bars, you don't tend to notice and if you find it lying loose on the garage floor days later you wonder what the hell it is. It's really a consequence of it being greased up by the factory that it falls out so easily. It's a weird shape, I have quite a few NOS lying around, genuine Honda not repros, I'll see if I can take a pic. In essence they are like a tank track with the middle dipping inward on the upper edge, not sure if it does that same on the bottom but probably, just off memory here.

As for the ball covering, yes they are rubber and they aren't exactly easy to fit either. Maybe the supplier originally dipped the lever ends but Honda found they were easily damaged and had replacements made in rubber as a result. Not economical to replace the entire lever for a small scratch in the lever end, hence the replacement. Your statement saying they were dipped was misleading as it inferred they couldn't really be replaced, which as we now know isn't exactly correct.

I've never claimed to be an expert on SOHCs Graham, the signature may say that but that's not something I've put on there, I dislike 750s for instance so I never really bothered to learn that much about them, 350 fours I know very little as they weren't really imported into the UK, 400 fours I don't mind, did quite a few back in the day but my favourite SOHC was and always will be the 500 four. I know a great deal about them as they interest me, hence knowing that the ball lever covering was available as a spare part. I'd appreciate the constant sniping of my comments you've been doing lately would stop, just because I started to sell camchains to members on here and in your words "was taking food out of my mouth" you've had a bag on ever since. I appreciate your not well and that's why I've not really said anything before but if you want to start slinging dirt that's fine but be prepared to get muddy as well.

It was not a sniping at you. I was just putting you straight on your comment which was wrong information, that the ball cover was not dipped. When the original levers came with a plastic ball cover and not rubber on a original lever. I hate wrong information given out and i will correct any incorrect information given by any member  ;)

Well given that his question regarded replacing the plastic shield so it matched the other lever and thus to me meant he was looking to restore his present levers to original whose answer was the correct one?  I'd say mine as he can easily buy the ball covering so getting the lever back to standard, much less hassle than trying to melt plastic onto it. That was why I posted they were available, I personally wouldn't even know where to start on melting plastic for that job as most plastic doesn't really lend itself to that sort of treatment in my experience. I suspect that originally the plastic used was brand new and not recycled so it could be used that way, same for the clear plastic, which tended to start to flake apart after a few years in the sun leaving you to pick the rest of it off so it didn't scratch your fingers.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on April 05, 2022, 12:29:13 PM
Today’s problem is below - the badly pitting carbs lifters. Extremely light - they feel like plastic and yet are obviously a metal.

Q - can this be re-chrome plated ok… and if not, suggestions for a good looking finish.

Ta.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Oddjob on April 05, 2022, 01:56:45 PM
Looks alloy to me. I'd spray it myself.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: AshimotoK0 on April 05, 2022, 02:39:13 PM
One for the alchemists….. Ash!

1/4 of the Airbox to Carb manifolds has mummified around 25% of the belmouth, ie the portion within the ‘box. The rest of it, and it’s siblings, are brand new pliable - which they should be as only a couple of years old. Heat makes it pliable, but on cooling we’re back to square 1.

Asking for Wintergreen draws stares here - unheard of. I can find some on eBay… but at a price.  So… does this mix of WG + alcohol (Isopropyl) REALLY work… or should I just spend the $$$ on a new set. (not cheap ☹️)

Notably these manifolds are not actually rubber (?) - and more of a shiny neoprene (?)

Ta again.

I used Reofos 50 but it's not readily available. I used to be able to get it from the old company I worked for 25 years ago but lost all of my contacts now... the chemist guy who put me onto it did suggest a more readily available alternative .. I will try to contact him.  https://polymer-additives.specialchem.com/product/a-lanxess-reofos-50

Rubber in this Youtube  video clip was rock hard to start with but after Reofos treatment remained supple even when cold and still is the same 7 years later  ;)


https://www.youtube.com/shorts/Y1kVSlLnR8k
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on April 14, 2022, 12:44:20 PM
It seems a fair bit of this thread has gone walkabout ….

A big thanks to you Oddjob, I took the bull by the horns and went for broke in sanding the badly pitted carb lifter. Initially I used my small (10mm wide) belt sander with 120 grit, followed with 200 Grit. Then Dremel bits (+ soaps) followed by the 6” polishing wheels / (grey / brown / white soaps) on full sized bench grinder machine. Good as new - amazed!

(The Dremel OEM bits are prohibitive - I got the set you see here off eBay for £8 delivered!)

Ash, the Wintergreen arrived and the manifold soaking as I write. It is softening (@ 24 hrs) but so far, has not showed signs of returning to original shape. 🙁
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Oddjob on April 14, 2022, 12:47:54 PM
Be careful now, once the polishing bug bites you start to look around and see the potential for other bits to be done.

Good result, might have some competition at last  :D :D
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: K2-K6 on April 14, 2022, 03:56:29 PM
A couple of post I put on here have gone missing, about the material used for these.

To reinstate,  the cast material just may be a magnesium alloy as it does feel very light, but also very rigid.  It has that magnesium-ee feel to it.

If that were the case, then the plating may be significant as protection against corrosion with these alloy being quite vulnerable.

https://www.arlingtonplating.com/substrates-specifications/plating-on-magnesium/ gives some insight. 
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on April 14, 2022, 10:28:35 PM
…. you’ve worried me now Nige as I had to remove a fair bit of corrosion to get down to unspoiled metal. Happy though that I never (obviously) broke through to any base metal, nor had to remove any material from the critical dimension parts.

I’d say you’re spot on with the magnesium alloy thoughts, it certainly does feel lighter than aluminium, has a solid ping to it, and fits in with the descriptor of it being used in the automotive industry for paddle shifters etc.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Oddjob on April 14, 2022, 11:37:24 PM
Try setting it on fire, if it goes up like a bonfire I’d say it’s most likely magnesium alloy.  ;D ;D
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on April 14, 2022, 11:45:34 PM
… you’re a funny man Ken, however, I’ll pass on this one 😂
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on May 01, 2022, 01:11:13 PM
Can somebody tell me what the ‘Sprocket Side’ plate’s job is, and the original finish pls (black matt / gloss, zinc, or chrome?)

At the mo non-existent on my K2.

Ta.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: K2-K6 on May 01, 2022, 04:28:44 PM
Unsure if it's right, but always thought it's function is to stop a loose/failed chain falling between the swingarm and sprocket face, then jamming on the securing bolts to lock the wheel.

Early experience with some chain failures on the 750 may have caused this path to be explored.

As initially noted, I'm not sure and haven't any significant information to confirm this is correct.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Oddjob on May 01, 2022, 04:34:01 PM
The 500 one was certainly zinc plated, sort of a dullish grey. I'd imagine it copied the 750 in finish. I don't think black ones came in until much later.

The were not only functional, as in what Nigel has described but also decorative as the sprocket was covered and lets be honest, a sprocket isn't that attractive to look at. Now you can get them in gold etc that's changed.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Nurse Julie on May 01, 2022, 09:56:40 PM
Zinc is correct for a 750K2 .
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on May 14, 2022, 03:43:30 AM
Can anyone advise how to separate the chrome cap from the rest of the gubbins please? Tried heat + gentle prying - to no avail.
Not esp happy to try a threaded bold through the lower cap holes to push against the chrome top ….

(Wanting to re- gold passivate the lower cap)

Ta.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on May 14, 2022, 03:54:05 AM
Hi Ash,

Wrt to my hardened airbox rubber and Wintergreen - sorry for the late reply….

Oddly, only 25% (circumferentially) of one rubber has mummified, and whist heat would soften it, within minutes it’d be back to its new norm.  I then put it in a jar of 25% Wintergreen oil + 75% isopropyl, and have left it there for weeks. It’s much better, but still retains a little hardness. Most surprisingly it’s shrunk in overall size - to the point of being unusable.

Can’t work it out, OEM and the other 3 fine. It’s defo the runt of the litter…

For the price of a single replacement I’ll skip trying to source Reofos 50 and call it a day 🙁 . Thanks nevertheless!

Cheers,
Simon.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on May 19, 2022, 05:01:28 AM
A bit miffed last week as Autosol polish removed the Gold Passivate from the dipstick and Voltage regulator….

Managed to separate the dipstick components by drilling a 5mm hole in the circumference, and then tapping in a blunt 5mm grub screw to prise the chrome cap off. Worked a treat.

Dipstick innards + VR cap zinc planted and passivated - pleased with the results.

Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on May 24, 2022, 12:31:51 PM
This restoration is getting deeper and deeper 🙄.

Anyways, because I’ve now decided to powder coat the frame, the loom is out, and looked a bit grubby. So, no dishwasher for me, but rather the (heated) Ultrasonic cleaner … and it’s come out like new. The question now is… will there be extensive water / damp in the loom runs and should I de-construct / rebind with fresh tape?

In my gut I reckon I should, as years ago I renewed a 400F loom, and kept the old (original) for spares. What shocked me was finding splicings within that loom, simply twisted together… no solder… nada. If the 750 loom has the same, well, I’d rather fettle it now.

Thoughts…?

Edit - I might have answered my own question since studying the circuit diagram & noting numerous internal splicings, primarily in the live (Black) and Earth (Green) runs. I guess if the first I come across is soldered / crimped I’ll stop; otherwise it’ll be a full re-sleeving / making good splicings.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: K2-K6 on May 24, 2022, 01:49:36 PM
On balance I'd agree with further inspection to asses where it's at.

Is the outside non adhesive "self almagamating" tape on these? Common on looms generally and doesn't make all the contents sticky.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on May 25, 2022, 05:48:24 AM
Thanks Nige, for some reason I never thought of using self amalgamating tape. (loom using conventional electrical tape - ugh)

But, the good news is the loom’s been nicely put together with quality crimps and insulation - so my plan is to not bother stripping back further. Phew.

Title: Re: 750 K2 Strip & Rebuild - help please
Post by: K2-K6 on May 25, 2022, 07:30:35 AM
Good news if it's all good Simon, certainly makes it easier than diagnosis in situ after a reassemble  :)

As part of apprentice training we had six months in electronic section and making looms etc to aircraft standard complete with design protocols that would allow at least two repair when installed with designed in loops etc along with precise cable tying in old style.

Soldering exercise, they had us make a cube of rigid wire panels all soldered by hand to make the matrix and inspected for solder flow, fillet geometry etc. Then as final test the instructor placed the cube on the floor and stood on it (all sixteen stone of him ) a ritual cruel exposure in front of the training group, with mine one of three to survive the stress test. Still smug now  ;D ;D
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on May 29, 2022, 10:39:30 PM
Pity you don’t live next door Nige; I’m sure I could find you plenty of work… later this year plan to rewire the Kombi with all the horrors that go along with that. (still undecided whether to modify the connectors / fuse box / terminals etc.).
With your amalgamation tape idea have now fully striped the K2 loom, washed it again, and will resheath it this week.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on May 29, 2022, 10:56:34 PM
An interesting last Friday with Lindsay, who is rebuilding my K2 engine.

The first job was new cushs into the Primary drive sprocket component, which had to be disassembled due riveted. Within there are 12 cylindrical rubber cushs; at 50yo they were rock hard and if deformed slightly  (using a pliers) simply split and stayed that way. We stuck ‘em in a bag, and when I put it down on the bench there was a solid clunk like it was a bag of marbles.

Initially 2x new needle roller bearings were pressed into the shaft. Next the 12 new cushs went in to the lower sprocket, with upper sprocket then pushed in place. (needed a press to coax this - very tight). Then finally 6 new Allen screws, into the holes pre tapped and countersunk, using thread locker of course. All now good as new.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on May 30, 2022, 11:03:03 PM
More progress on the engine rebuild…

The cases blasted, and despite being told 99% of the beads cleaned away, an amazing amount still came out. We thoroughly washed, (air line) blew all casings, dried them in an oven, and repeated the whole process. Fingers crossed, it really is aggressive stuff.

Next sprayed the cases with a HT Silver, before baking at 180C for an hour. Then the rebuild, which went quickly and with little fuss. I’d cleaned all parts thoroughly, and supplied all new bearings, seals, chains…. and re-zinc plated all fasteners. All gear dogs + mating faces undercut on both drive and overrun sides.

Head away this morn for valve work, barrels being rebored 0.5mm os.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: McCabe-Thiele (Ted) on May 31, 2022, 10:57:31 AM
All looking good but can't see any assembly lube or is it colourless?
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on May 31, 2022, 11:30:03 AM
Yup, graphite oil on big ends and mains, otherwise squirts of oil in all bearings / moving bits as we progressed. I’ll agree; it looks drier than it is…
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: K2-K6 on May 31, 2022, 02:07:19 PM
The best bit, building them again after detailed preparation.

Always amazed at just how much research and development went into these engine, such nice details within those cases  :)
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on May 31, 2022, 11:07:03 PM
It really is a thing of beauty, and fiendishly compact. Cable oiler very cunning; though will be ‘turned off’.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on May 31, 2022, 11:10:19 PM
Have some surplus VHT Silver paint, originally destined for the CB750 rebuild but not used. It boasts 1000+ C, and mentions exhaust systems etc. Q. How would it perform on non-hot components - specifically the carb on the old Kombi; which is out & in bits, so might as well get a bit of love…
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: smoothoperator on June 01, 2022, 09:47:10 AM
The VHT paint seems pretty tough stuff to me, but that is after curing in the oven. So if you are confident to put whatever part in the oven for an hour or so, I would say it would be worth a shot, even if that part never saw 150 C again. Maybe it would be a bit soft if it wasn't cured, and obviously you are looking for petrol resistance if you are painting a carb.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: K2-K6 on June 01, 2022, 12:10:59 PM
Have some surplus VHT Silver paint, originally destined for the CB750 rebuild but not used. It boasts 1000+ C, and mentions exhaust systems etc. Q. How would it perform on non-hot components - specifically the carb on the old Kombi; which is out & in bits, so might as well get a bit of love…

Unsure of predicting an outcome because of zinc-ee base material. Painted carburettor are few and far between and maybe because of this element, unable to competently adhere to zinc prominent metals.  It's decomposition being a protective strategy with micro surface conversion to zinc oxide (I believe) giving this characteristic, a little like self anodizing in effect.

Doubt if it will cause any difficulty, but may not be longer term permanent because of above reason. The paint should survive but may not be attached sufficiently to the casting to avoid bits falling away.

For zinc surface consider it like painting/priming galvanised items, so maybe a competent base layer would assist here.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Oddjob on June 01, 2022, 02:57:08 PM
I've never had a problem getting paint to stick to carb bodies Nigel, the linkages though are another problem.

My current 500 restoration features sprayed carb bodies with petrol resistant lacquer on the spray paint.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on June 04, 2022, 09:25:35 AM
Kombi carb body painted and baked @ 200C / 1 hr. Other bits plated. Annoyed at myself for not dressing the screws < plating; will do better next time 🙁

Thanks for the helpful comments…
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: royhall on June 04, 2022, 09:38:54 AM
An interesting last Friday with Lindsay, who is rebuilding my K2 engine.

The first job was new cushs into the Primary drive sprocket component, which had to be disassembled due riveted. Within there are 12 cylindrical rubber cushs; at 50yo they were rock hard and if deformed slightly  (using a pliers) simply split and stayed that way. We stuck ‘em in a bag, and when I put it down on the bench there was a solid clunk like it was a bag of marbles.

Initially 2x new needle roller bearings were pressed into the shaft. Next the 12 new cushs went in to the lower sprocket, with upper sprocket then pushed in place. (needed a press to coax this - very tight). Then finally 6 new Allen screws, into the holes pre tapped and countersunk, using thread locker of course. All now good as new.
Interesting write up on the cush rubbers. I wonder what makes the rubbers rock hard on one rebuild but still soft and pliable on another, after all they are all a similar age. I was going to do mine, but after a good prod through the holes they feel as good as new. Maybe the type of oil used or mileage? Anyway I wasn't complaining as it's a pig to do, just wondering.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Sesman on June 04, 2022, 11:04:29 AM
Yes, shock rubbers…..🤔. When I stripped my 77 550F2, I found the primary chain to be approximately 60-70% worn (that’s a dimensionless estimate based on comparison with new), but remarkably the primary rubbers were comparable with new in condition. I replaced them anyway. The motor showed absolutely no signs off being dismantled in the past. So primary rubbers seem to be something of a mystery?
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Sesman on June 04, 2022, 11:07:53 AM
……though I believe others on this forum find that the ‘norm’ is to find them as ‘hard as marbles’.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on June 04, 2022, 01:06:47 PM
My guess is (my) old rubber cushs had little useful deformation ability left given what I saw; but given their loadings so uniformly applied I’d agree they might have gone on forever - with little real indication to any rider. (tho’ time will tell on this one).

As the first cush came out in my hand, there was little obviously wrong with it…. and I stated so. Lindsay got a pair of pliers and squeezed it… it split and deformed - as any old rubber would. When a new one was in my mitt the difference was then very apparent; rubbery rubber versus hardened.

There was a choice for me…. at extra cost of course, but I figured we were in so deep it was better to go the extra mile. The bike is 50yo, the cushs have experienced numerous heat, compression / decompression cycles, and like the rest of us, must be getting a bit tired and stiff!

In my case, no regrets having seen the old pieces….
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on June 18, 2022, 01:14:12 PM
It seems Roy & I pretty much neck in neck… though it’s certainly no race at the pace I work.

Engine now complete, and very pretty. Head completely reworked, with valve guides re-lined, new seats, valves worked. Bores taken to 0.5 o/s, with new Cruzinimage pistons.
New chains, seals, bearings, primary cushs, cam tensioner / followers, and obviously painted & baked. Old clutch refitted as in gc.
Starter motor now with new brushes, positive wire…and painted.
Frame and all black components powder-coated.

Various bits now Cobalt-Nickel plated, which is a pain as needs to be done at 50-60C for an hour, and best preceded with a copper ‘flash’ plate (15 mins / 50C). My garage looks like something out of breaking bad. The toolkit freshened up…

Carbs and wheels next.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on June 18, 2022, 01:22:15 PM
Comments please…

Currently the wheels with SS spokes, which have been fine over the past 10 years, but notably 3 or so failures on the rear wheel in those spokes with the acute bend. Luckily these are the ones that are easily replaced by deflating the tyre enough to unlace the bad one and thread in a new…

Anyways, am planning to polish both hubs, and so will be dismantling the wheels.
Thoughts please on switching to Chrome spokes versus SS. Notably the bike will be ridden regularly, and that I live on the coast. Low maintenance and retaining good looks are key…

Ta.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: K2-K6 on June 18, 2022, 06:59:38 PM
Engine looks good. For spokes I'd favour stainless with brass nipples and using molybdenum grease on threads to build and tension them.

Consider judging the load on the tight turn spokes in comparison to the less angled (are the breaking spokes the outside on hub) that may improve longevity for you as that doesn't seem that bad for current spokes in lifing terms.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on June 19, 2022, 11:44:09 AM
Thanks Nige; some good advice and I’ll rebuild using SS and arrange a bit more pong than ping on the B Spokes.

Today’s question on the (K2) carbs.

(1) any tips to getting the top rubber seal out so that I can properly service / polish the  carb top? (Pic #1)

(2) any tips on getting the polished strip concealing the choke mechanism out? Better still, does it actually need to come out to replace the mechanism? (Pic #2)

Ta…
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on June 25, 2022, 12:40:16 PM
Needing help form the Alchemists…. Ash, Nige etc.

Plating today, specifically Cobalt-Nickel onto carb fittings. All gone very well…. barring the ‘anchor’ bit that screws into the slider and holds the riser bar in situ. The red flag came up as I gave them a short acid pickle prior to the copper Ultra Strike plating… rather like dropping an Alker seltzer into a glass of water… ie a lot of fizzing.

So, the flash copper coat went on, but not great. I continued with the Cobalt Nickel, one piece came out fine, the other three a mess, with patchy black streaks. The plate obviously didn’t take.

I’m not sure of the metallic make up of these bits, tho’ they are magnetic. Not sure how to proceed tomorrow… any thoughts whether Zinc plating will take? If not, what next?

Thanks
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on June 25, 2022, 12:57:19 PM
One the plus side to the above post 90% of plating today was a great result. The pics say it all - even if the first two are upside down 🤦‍♂️.

The cable pulley wheel was a real sod, in that it’s two plates riveted together, and sandwiching 50 years of oil. This, of course, felt the need to leech out in the plating, which set me back a day with streakings. An overnight soak in petrol, followed by multiple heated ultra-sonic bathes finally got me where it needs to be.

Do I enjoy it? Not a bloody bit - it’s an awful lot of prep, and in the case of the copper strike and Cobalt-Nickel they’ve to be done at 55C or so which just makes it a bigger logistical pita. This all said, I am appreciating the freedom the plating kits (ie inc Zinc) are giving me in that ANY bit of metal on the bike is now doable on my own terms; and if done methodically can be minimised to a point. The nice bit about the Cobalt-Nickel plate is that it’s the next best thing to a chrome look, and a whole lot cheaper & safer to do. Did the brake torque arm last week - @ 50yo looks just fine now.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Trigger on June 25, 2022, 02:03:03 PM
You have to keep a eye on the pully wheel ( Butterfly ) as, it has alloy rivets and any type of Pickling weakens the rivets.

As per factory they were BZP with a yellow passivate and riveted together after plating  ;) 
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Oddjob on June 25, 2022, 03:19:09 PM
Not that hard to make a new one if it does break though, made one for the 500 earlier this year. Tweaked how to do it now to improve how it comes out.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on June 27, 2022, 12:33:59 PM
Cheers Graham. The passed couple of months I’ve been using the Sandcast as my go-to reference for the K2 rebuild (when in doubt), but alas that doesn’t have the pulley wheel. And tbh, I didn’t give it a thought…

So dang when you pointed out the gold passivate finish! (& thanks). Fixed now…

And yep, the acid wash… basically 30 secs in a weak solution followed by a distilled water rinse - ie not concerned wrt hydrogen embrittlement (which is fully covered in the plating manual)
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Oddjob on June 27, 2022, 01:14:31 PM
They came out nice, your getting good at this lark  :) :)
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: McCabe-Thiele (Ted) on June 27, 2022, 01:55:05 PM
That's an impressive bit of plating you have done - looks like new.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Trigger on June 27, 2022, 02:08:24 PM
Cheers Graham. The passed couple of months I’ve been using the Sandcast as my go-to reference for the K2 rebuild (when in doubt), but alas that doesn’t have the pulley wheel. And tbh, I didn’t give it a thought…

So dang when you pointed out the gold passivate finish! (& thanks). Fixed now…

And yep, the acid wash… basically 30 secs in a weak solution followed by a distilled water rinse - ie not concerned wrt hydrogen embrittlement (which is fully covered in the plating manual)

They look perfect  ;) I only found out that they were alloy rivets when i got them back from the platers years ago in two parts and had to re-rivet them using old Land rover body rivets.
 
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Matt_Harrington on June 27, 2022, 05:25:31 PM
Excellent plating. I bought a kit 15 years ago and have just unearthed it. If I can get my parts half as good as that, I'll be happy!
Matt
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Oddjob on June 27, 2022, 09:58:54 PM
If you unearth it then it won't work  ;D ;D

I'll get me coat.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Sesman on June 28, 2022, 05:59:22 AM
Boom, boom. You ground that one out  :)
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Matt_Harrington on June 28, 2022, 09:44:47 AM
If you unearth it then it won't work  ;D ;D

I'll get me coat.

Gawd!  :D :D
Matt
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on July 01, 2022, 12:42:08 AM
Bench carb set-up…

Know about the 3mm drill trick in initially setting the sliders - but which end of the carb to stick it in?!

If I use the engine manifold side (straight skirt, and from a previous SOHC post) I’m left with abouts 7mm of thread protruding above the adjuster lock-nut. This goes against my manual suggestions of 1-2mm, which was also what I had when I dismantled the carbs… (ie 1.5mm)

If, otoh, I go for the Airbox side (domed skirt) I do indeed get the 2mm free thread, but virtually closed throat on the opposite side. 

Cheers in anticipation….

Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Oddjob on July 01, 2022, 01:02:50 AM
It's meant to be a closed throat on the other side as this is how the carbs are at idle.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on July 01, 2022, 01:17:28 AM
Cheers Ken. This fits with the 2mm (and my carbs @ dismantle) free thread spec, and suggests the drill goes in the domed skirt / airbox side. That however, seems to be in confliction with other posts I’ve read on this SOHC Forum.

Ho hum.. will go with your advice / the 2mm free thread spec.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Oddjob on July 01, 2022, 02:16:09 AM
Actually I may have it the wrong way round. IIRC the drill bit goes into the engine side as that the gap the carbs need to idle properly. The idea being that they are all the same gap when you fit them and you then adjust the idle speed correctly using the large screw on the linkage bar.

In the bottom pic it's the left hand carb which is orientated correctly for the drill bit.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: K2-K6 on July 01, 2022, 06:11:05 AM
Actually I may have it the wrong way round. IIRC the drill bit goes into the engine side as that the gap the carbs need to idle properly. The idea being that they are all the same gap when you fit them and you then adjust the idle speed correctly using the large screw on the linkage bar.

In the bottom pic it's the left hand carb which is orientated correctly for the drill bit.

Agree with this to set on bench.

Initially set the threads as you want to match original Simon, then turn the "master" tickover screw to lift all the slides such that you can get the drill of choice underneath the #2 throttle slide like a feeler gauge just sliding fit. Now set the other three carb with that same drill as feeler gauge with their own threads to get parity. Once it slides concisely into all four you've equalled them as a set.

Now bring that "master" control back down to their closed/running position to set them ready to start the engine. 

Once it's up and running, don't reset the carb balance (it will be correct iif done accurately) and allow running in to be completed and then valve gaps etc to be confirmed/reset to specification (these gaps will affect vacuum reading and so shouldn't be relied upon during this period) then take a reading of vacuum if you need to quantify it.

It's an odd situation (often propogated by statement of "just needing a carb sync") but mechanical accuracy in setup will hold absolute technical priority over vac gauges if done with diligence.  It's primary function is to set the slides at parity for full power balance (this is not measured with vacuum gauges) with conditional low speed running as a side benefit of it.

Fine cylinder "tickover" balance is completed with individual airscrew optimisation in finally setting that smooth running. 
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on July 01, 2022, 10:02:37 AM
Carbs finished - everything possible to be done… was done.

Thanks Nige - all makes perfect sense. The only remaining question is ‘how much’ gap to finally leave wrt the “closed / running position”…. 01mm, 0.5mm? I do have the original ‘thread remaining’ figures, and so indeed could roughly set this.

(To labour the perfect sense bit; I’m left bloody wondering why I bought a set of vacuum gauges 😂, though am indeed happy to leave ‘em in the cupboard!)

Many thanks,
Simon
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: McCabe-Thiele (Ted) on July 01, 2022, 10:14:54 AM
Wow the complete carbs look brilliant - factory fresh if you will - that's a lot of attention to detail.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on July 01, 2022, 12:24:14 PM
Cheers Ted, appreciated. It took a fair bit of time and effort - hoping it’s repaid in full!
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Sesman on July 01, 2022, 01:07:48 PM
Do not fit those to a dirty, foul smelling motorcycle.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on July 01, 2022, 01:36:55 PM
…don’t worry!
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: K2-K6 on July 01, 2022, 01:58:36 PM
"Thanks Nige - all makes perfect sense. The only remaining question is ‘how much’ gap to finally leave wrt the “closed / running position”…. 01mm, 0.5mm? I do have the original ‘thread remaining’ figures, and so indeed could roughly set this."

This doesn't matter as you'll be setting the rpm as soon as you start it, so just eyeball it to nearly closed as it will mean you have to use the twist grip to start it running if it's just a little too closed.  The whole setup routine (Bryan method) establishes the components in the correct orientation one to another to give  potential for in use service adjustment in either direction needed. The final closed gap is always going to be dependent on rpm when running.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: K2-K6 on July 01, 2022, 02:15:06 PM
'(To labour the perfect sense bit; I’m left bloody wondering why I bought a set of vacuum gauges 😂, though am indeed happy to leave ‘em in the cupboard!)"

It's certainly become folklaw that using vacuum gauges is the right route to correct any sort of unspecified maladies  :) and very wrongly used in someone hoping that it's going to fix their particular problem.

It will of course only fix the slide balance from one to another IF it was wrong in the first place. Also conditional is that all other service items should be resolved first PRIOR to setting with gauges, else you'll establish a fault by wrong reading.
They are a convenient way of setting carb balance if used appropriately (and don't require a workshop to remove carbs to complete) but only with re-establish and accurate prior routine. Often given as a solution though from unreliable scources.

There's a different use though on one bike in these SOHC engine and that's the four cable carbs. They are used to set the individual slide position and balance at idle (there's no master lift parity on that system) after which the in service adjustment is done equally by the "clock face" grooves on the slide stop position screw to keep them that way.
Also at a higher rpm too when the parity of the cables is tested independently of their stop position, this to give full load parity (again because it's not controlled be the lift bar) and important for cylinder balance under maximum torque running. Certainly there's more value there from owning gauges, but most don't don't know why that detail exists in the Honda manual.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Bryanj on July 01, 2022, 02:47:16 PM
Using the small drill bit ses the slides at the same height which gets you close but the gauges then take into account all the minor manufacturing imperfections in the carbs
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on July 02, 2022, 02:00:06 AM
Well Bryan, that’s thrown the cat amongst the pigeons in my wee brain…. I was ready to mothball the vacuum gauges.

Did Honda (ie dealerships) routinely vacuum gauge their bikes at the standard valve service intervals? I genuinely thought it was a ‘set & forget’ type procedure, which was never really necessary unless major works had been required.

I definitely like and respect the idea of mechanically matching the sliders once and for all, and ask whether valves set iaw the manual have a significant effect upon MPs and warrant de syncing those sliders? Would you not end up chasing your tail over the years?

Specifically, my 750 has been rebored, new pistons, rings, and a comprehensively serviced head… to the point that any (In/Out) valve could go into any (In/Out) seat (I never knew such tolerances existed). The carbs have been fully serviced. So, in my case here, is there a case for simply leaving alone once bench set?

An interesting topic - appreciated.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Bryanj on July 02, 2022, 07:26:46 AM
I think carbs were supposed to be checked at first service and then every other major service or annualy and if everything else was adjusted first were frequently inside tolerance but rarely exact.
Always checked after major work and then at first service afterwards, or if removed/disturbed for any reason
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Sesman on July 02, 2022, 07:33:03 AM
I have a set of mercury vacuum gauges from the 70’s. I can honestly state that all the multi cylinder bikes I owned in the 70s and very early 80s benefitted  from regular carb vacuum balancing. The improvements were very notable on the 400/4 and Suzuki 550 fours I owned. The mech sync will provide a reasonably accurate physical/dimensional sync, but the vacuum gauges iron out any differences in fluid dynamics created by manufacturing tolerances and inlet flow characteristics. I guess it depends on how fickle and fussy you are with the set up.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: K2-K6 on July 02, 2022, 08:01:05 AM
Original manual, 1970, for 750 calls for carb checking firstly at 3000 miles in service schedule, then check at 3000 mile interval. And that's for the four cable system.

Certainly by setting them mechanically but then putting the gauges on will confirm or dispel something of this topic just from the readings that are present.

I feel that review of this element is significantly skewed by not fully appreciating the role the airscrew adjustment takes in setting these up, which most contemporary workshops didn't even have significant understanding of when working with them.  The adjustment of most carb rack slide position has insufficient resolution to fully trim the cylinder parity at idle which by design is completed by the idle mixture circuit. That strategy is a sound one and transferred to fuel injection system on virtually all current engine, in that the flywheel pulse monitoring is used to trim fuel quantity for each cylinder to bring smooth idle irrespective of intake tract variances.  This is the same as these carburettor (they are particularly well designed) in working with cylinder energy output to give idle parity which then is ignored as throttle gets wider open.

Carb slide position (at idle) is not the right tool to compensate for cylinder to cylinder casting/flow variation as you'd need the maximum flow at full open to control that condition. It would likely give unavoidable poor refinement at idle though, if needed.

Title: Re: 750 K2 Strip & Rebuild - help please
Post by: K2-K6 on July 02, 2022, 08:17:28 AM
Essentially the vacuum measurement is only controlled (at idle) by the geometry of the space under the throttle slide, that's a small part of the venturi arc in combination with the underside of the slide itself. It cannot take into account most intake tract variability as they would lay outside the scope of influence of the above named parts.

Likely to be more affected by piston ring sealing (pulling the vacuum to be measured) more than anything else, and probably why Honda don't call for monitoring until running in is well out of the way.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Sesman on July 02, 2022, 08:27:27 AM
Interestingly the Suzuki 550 models of the era had a higher vacuum setting on the two outer cylinders than the inner two.

The rules for best results are to mech sync then vacuum sync with instruments. Then check at regular intervals….it works.

Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Bryanj on July 02, 2022, 10:24:02 AM
Now im awake--ish.
When at Meads i had to do a full sevice job on one of the 500 V4's and was trying to get the carbs closer, after 4 hours of peeing about cos we didnt have the correct double bent screwdriver tool i gave up and told the customer i was having problems and it would not be finished till next morning.
Came in fresh, pulled the carb bank and set them up with a 1/16 drill shank on the butterflies.
After reinstalling vacuum was well within book spec but not spot on so buttoned it up and reported as within service spec, customer went away and came back saying he was very happy and thought it was running best it ever had plus thanking me for being honest,
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on July 04, 2022, 05:09:57 AM
Thanks all on the carb set-up info; all done & ready to be installed.

Todays problem is asking for tips to get the bloody rubber tray securely into the battery box. One of the pull-nipples long gone; the other with a nick. The rubber ‘lugs’ are suffering slightly from age (sound familiar?) but pliable enough I’d have thought. Despite applications of copious rubber grease they’re not showing any signs of compliance. Hands / knuckles now worn out…

Anyways, tip pls?
Ta.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Johnny4428 on July 04, 2022, 09:38:55 AM
Piece of thin cord or string round the back of the nipple a couple of times and pull through as the cord unwinds hopefully pulls the nipple through. Haven’t tried this method but saw it somewhere.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on July 06, 2022, 12:03:05 PM
Thanks Johnny; did try this on another nipple problem using waxed sail thread… it basically cut through said nipple.  I may try it all again, but with a thicker / gentler cord.

(1) Today unlaced the hubs for polishing. When rebuild time comes back any comments on greases / anti seize lube etc to go onto the (SS) nipples where they sit in the chrome rim?

(2) the (front) disc mounting plate is to be repainted black. Should it be gloss, satin.. or matt pls?

(3) since I’ve got the disc in my hand, any ideas how to de-glaze it? Been through past threads here but not found much other than to buy a new disc.

Ta.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Johnny4428 on July 06, 2022, 07:07:46 PM
Managed to refit mine with pull through nipples which were intact and a bit of rubber grease. Wasn’t too bad, but the disc pads on the sides of battery box were a pain in the butt! I think the inner disc plate is satin, but i think there is someone with more knowledge waiting in the wings that will confirm.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on July 07, 2022, 12:44:09 PM
Onto the wheels / hubs today. Can anyone pls advise which of the below will rust / quickly look shabby - certainly I can plate but prefer not to where possible.

#6 I reckon definitely needs a zinc coat as seems ‘straight forward’ steel plate; but the other pieces?

Ta.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Oddjob on July 07, 2022, 03:11:58 PM
No 6 was chromed IIRC. All of them will rust but some are internal and so are protected to some degree. Axle nut will rust on the outside edges, the spacers will especially where the seal doesn't rub as the rubbing keeps the rust at bay. I had most of mine hard chromed, they grind them back to standard spec in most cases and they tend not to rust after as the chromes so hard. The speedo drive I'd plate, makes no difference in that case, the speedo drive plate you could try rechroming or BZP it.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: K2-K6 on July 07, 2022, 04:16:08 PM
Thanks Johnny; did try this on another nipple problem using waxed sail thread… it basically cut through said nipple.  I may try it all again, but with a thicker / gentler cord.

(1) Today unlaced the hubs for polishing. When rebuild time comes back any comments on greases / anti seize lube etc to go onto the (SS) nipples where they sit in the chrome rim?

(2) the (front) disc mounting plate is to be repainted black. Should it be gloss, satin.. or matt pls?

(3) since I’ve got the disc in my hand, any ideas how to de-glaze it? Been through past threads here but not found much other than to buy a new disc.

Ta.

1/ a consideration regarding spoke breaking from a few post back. Make sure that the hub flange casting doesn't interfere with the internal spoke radius of those outside set of spokes to bring a high stress alignment with the new spokes. Carefully checking that they should be slightly "bellmouthed" to avoid pulling the spoke angle tight over a sharper radius than the spoke will help to distribute load along the spoke. Hope that makes some sense  :)

3/ disc deglaze, if you mean surface for brake performance rather than refinished surface to get level from irregularity? Then just using sintered pads is fine as it'll have no problems. Just clean with isopropyl alcohol before use or acetone/brake cleaner proprietary spray.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on July 09, 2022, 09:03:33 AM
Thanks Ken / Nige, and yep, all makes perfect sense.

The wheel bits, barring # 6 above, were all zinc plated it seems…. as a check I pre-dipped them in a stripping solution and over 15 mins the zinc fizzled away. Don’t know if it was the original coating, but they were indeed a bit tired looking, prior of course, to all of this. (The polishing pic above gives a false impression!)

Anyways, all Cobalt-Nickel plated now, and whilst not perfect will hopefully provide a better protection than their failing previous coatings. Fingers crossed…

(btw: hub in the early stages of polishing - not coated in any way)
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on July 14, 2022, 12:57:51 PM
Painting the support plate to the front disc…. today’s tech question is, “How hot might the disc typically get on your average gentle run?” I ask because I have a SATIN BLACK VHT paint in the cupboard, whose quoted max temp is 140 C.
Am happy to take recommendations on any particular paint of course.
Ta.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: K2-K6 on July 14, 2022, 03:29:15 PM
With a "licked finger in the air"  calculation, that appears ok to me. The centre generally stays much cooler than brake surface in use even at fairly extreme elevations of rotor temperature. 

When you see brake discs at very high temperature, indacated by blue colour, it rarely extends much into the centre structure even on single material disc and with much less transfer on composite aluminium/steel type.  Also probably significantly above your intended use range too.

Maybe someone has some real numbers that would give more accurate experience to contribute.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on July 14, 2022, 11:07:03 PM
Thanks Nige - I’ll go ahead at that. I regularly use an IR thermometer for various things (eg plating bath, painted parts in the oven…); and first ride out, purely out of interest I’ll, check the disc temp.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on July 18, 2022, 12:42:44 PM
Wheels now done - the whole bike now fully reconditioned / painted / polished …and awaiting rebuild.

Begrudgingly I bought a wheel balancing / lacing frame last week (£120 thereabouts); the decision eased by knowing the MG Griso’s tubeless / spoked wheels (using o rings) will likely need replacing in the next few years.
TBH am pleased to have it. SO much easier / better / quicker than the wooden jig I DIY’d on the last occasion…

Anyone interested, the main tips I would suggest are (applic to CB 750)
TAKE A PIC < dismantling the old wheel.
(1) if you can justify a jig; go for one that will accept the rim + tyre dia; as adjustments / balancing then become possible down the track.
(2) Lace & true the wheel (initially) using the (20) A spokes only - ie those threaded from the outside towards inside of the hub. Fill all the alternate hub holes with those A spokes (ie both sides of the hub) and then lay it flat.
(3) Sweep all lower spokes in one rotational direction, and all upper spoke in the opposite direction…. iaw with the photo you hopefully took.
(4) Lay the rim over the hub & spokes, raising it appropriately so that it’s centreline  aligns with the hub’s, and lace the spokes in turn (upper / lower / upper etc) working around the wheel. (iaw your pic.)
(5) Mount the wheel in the jig, and true it for wibble and wobble (whatever the terms are)
(6) Now thread in the B spokes (it’ll be easy / obvious) and nip the nipples finger tight. (mine needed to be sprung in occasionally)
(7) Tighten B spokes (opposingly) to get a nice ping / pong sound.
(8) Check & adjust the wheel again for final trueness.

Well… it worked for me. Rebuilt / trued the second wheel in about 90 mins, inc the odd bit of help from the 2yo grandson…
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on July 20, 2022, 02:29:16 AM
Anyone finding issues with the YAMIYA Starter motor cover plate? Fitted a new one today, and left with a significant gap, particularly the leading edge. To be fair, refitted the old one and it too doesn’t ‘sit’ on its circumference, but rather rocks about the 2 starter motor top mounts, and still with a gap. Any yup, I’ve the new packing washer in @ 3mm thick or so… noting though that a 5mm one would solve the problem, but be visible due its height.

So.. is it a pattern part problem with the cover, or the motor….. or am I missing something?

Ta
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Nurse Julie on July 20, 2022, 08:06:16 AM
Have you fitted the rubber gasket under it Simon?
I've just looked at all our 750's and the cover all fit flush with no gaps, all have original covers fitted though. It almost looks like your starter motor is sitting a bit proud but that could be the angle of the photo.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on July 20, 2022, 12:32:37 PM
Hi Julie. Yea, I thought that too (starter motor proud), but as far as I can ascertain there’s no other way of installing it. (& thanks for thanking the time to check)

Yep, a silicon gasket is in place; about 3mm thick…  a 5mm piece would solve the issue, though would leave the chrome cover visibly raised.

All a bit confusing… unless it simply boils down to pattern parts?

Edit… I’ve had an idea, & tomorrow will swap the lid over with the Sandcast…
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Trigger on July 20, 2022, 01:42:59 PM
Don't know why you have acorn nuts on as, they came with M6 x 10mm chrome bolts and chrome washers as per picture. Are you sure the bolts are not too long  ;)

[attachimg=1]
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on July 20, 2022, 09:54:36 PM
Thanks Trig… knew about the M6x12 bolts, but ‘deviated’ a little - I wasn’t aware the bolts were chromed and will now revert - appreciated!

When tightened down the cover is hard against the starter motor mounts, and consequently high of the casing, and more-so at the leading edge. It’s as tho’ the starter needs to drop a couple of mm, and roll forwards a coupe of degrees. When I get home today I’ll be taking the SC cover off and seeing if it’s simply this as otherwise I’m baffled….
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on July 20, 2022, 11:34:34 PM
On topic here Trig / folk, pls how can you tell when a bolt set etc is chrome versus Zinc finish? I understand the colour code XW infers chrome, but don’t see it against fasteners.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Trigger on July 21, 2022, 12:03:31 AM
On topic here Trig / folk, pls how can you tell when a bolt set etc is chrome versus Zinc finish? I understand the colour code XW infers chrome, but don’t see it against fasteners.

You can not tell from part numbers on bolts and washers. Some nut have a S on the end of the part number to ID as chrome.

Honda superseded loads of nuts, bolts and washers from chrome to BZP, All the chrome bolts had smooth face apart from some JIS chrome screws.
The ones that spring to mind.
Fork drain bolts
Rear brake arm bolt
kick start bolt
Rear brake pedal bolt that had 0A on the end of P/N ( i have had them in Honda packets as, BZP and Chrome  :o
Chain adjuster bolt
Chain adjuster locking nut that had 0S on the end of P/N
Rear shock mounting bolts M10x32
And so on. The original general rule was a chrome bolt to a chrome part  ;) 
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on July 21, 2022, 01:45:30 AM
…good to know, and the ‘general rule’ is a big help, if not a little obvious now that I think about it!  Cheers Trig.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Trigger on July 21, 2022, 08:11:33 AM
Not sure what year they started all the superseding from chrome to BZP as, in the UK we had long running models like the CB750 and CB500 four.
By the time the CB550F1 came out there was very few chrome fasteners on the bike.
The only bolts i can think of that were not changed to BZP was, the indicator M6 bolts, top yoke bolts, nuts, washers , handle bar mounting bolts and the disc mounting bolts  ;)

You have also got all the different size nuts which may have the same thread but the A/F ( spanner size) were different. One of my pet hates was to see M8 bolts on the fork caps with a 12mm A/F when they should be 14mm A/F  :o 
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Bryanj on July 21, 2022, 08:20:07 AM
Trigger, the spanner size was because Honda used Japanese metric standards not ISO metric standard, you would have really hated the big tankers built in Japan, it was a nightmare after drydocking a German built one in Yokohama
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Trigger on July 21, 2022, 02:53:12 PM
Trigger, the spanner size was because Honda used Japanese metric standards not ISO metric standard, you would have really hated the big tankers built in Japan, it was a nightmare after drydocking a German built one in Yokohama

I know that it is all Japanese industrial standard Bryan, there are some M8 nuts with a 12mm spanner size and some with 14 mm spanner size. Also M10, 14mm spanner size and M10, 17mm spanner size, M12, 17mm spanner size and M12, 19mm spanner size and not forgetting many washer and nuts at different thickness  ;)
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on July 21, 2022, 04:22:00 PM
All rather confusing for the restorer as the fastener Part # does not specify the bolt’s finish. This arvo I googled the common part # for the starter cover bolt (CB750, K1, K2), and was ‘shown’ very ordinary (Honda packaged) BZP bolts. How does one know what is right?

Moving on, I looked more closely at the Sandcast Starter motor cover plate, and noted it too (just) fails the feeler gauge check… ie there is a discernible 0.5mm gap. I’m beginning to reckon the plates are non-OEM as everything else looks correct and original.

In the case of the K2 rebuild, and the new Yamiya plate, I’ve ‘fixed’ the problem by adding a thick SikaSeal adhesive base to the packing seal, ie raised it 1.5mm. For now, it’ll do until I get to the bottom of the issue….

One last query; one starter cover plate is mirror chrome, and the other a brushed chrome finish. Which is original pls?
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Oddjob on July 21, 2022, 04:56:50 PM
One nut that seemed to retain the chrome look was the upper shock absorber cap nuts and the big thick washers behind them.

Another was the pinch bolt for the rear brake arm on the rear brake plate. Same for the gear lever pinch bolt, some changed but some retained the chrome one.

Some fasteners do use an identifier on the end, modern Honda JIS screws for instance can be identified when they are black and also when they have a captive split washer, for use on handlebar switch gear for instance.

Oh just thought of another chrome bolt, rear number plate bracket ones, the 4 which attach it to the guard, they tended to be chrome with chrome washers, as did the rear light ones come to think of it.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Trigger on July 21, 2022, 06:49:06 PM
All rather confusing for the restorer as the fastener Part # does not specify the bolt’s finish. This arvo I googled the common part # for the starter cover bolt (CB750, K1, K2), and was ‘shown’ very ordinary (Honda packaged) BZP bolts. How does one know what is right?

Moving on, I looked more closely at the Sandcast Starter motor cover plate, and noted it too (just) fails the feeler gauge check… ie there is a discernible 0.5mm gap. I’m beginning to reckon the plates are non-OEM as everything else looks correct and original.

In the case of the K2 rebuild, and the new Yamiya plate, I’ve ‘fixed’ the problem by adding a thick SikaSeal adhesive base to the packing seal, ie raised it 1.5mm. For now, it’ll do until I get to the bottom of the issue….

One last query; one starter cover plate is mirror chrome, and the other a brushed chrome finish. Which is original pls?

The cover plate is flat mirror chrome. I have had a look at all my starter motor cover on 750's and all sit flat, not sure if i got them from Yamiya though  ::) If you are not having any joy contact yamiya as, they will take a new one out of the packet and test fit it to one of there bikes  ;)
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Trigger on July 21, 2022, 06:53:16 PM
One nut that seemed to retain the chrome look was the upper shock absorber cap nuts and the big thick washers behind them.

Another was the pinch bolt for the rear brake arm on the rear brake plate. Same for the gear lever pinch bolt, some changed but some retained the chrome one.

Some fasteners do use an identifier on the end, modern Honda JIS screws for instance can be identified when they are black and also when they have a captive split washer, for use on handlebar switch gear for instance.

Oh just thought of another chrome bolt, rear number plate bracket ones, the 4 which attach it to the guard, they tended to be chrome with chrome washers, as did the rear light ones come to think of it.

The rear number plate special bolts had chrome washers under them. Not all SOHC's and years came with chrome rear light bolts in chrome and the ones that did had chrome washers beneath them  ;)
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on July 24, 2022, 12:15:56 PM
Rebuilt the forks today, and tomorrow, will fill with oil.

Any recommendations (oil grade) to go for, or just stick with book figures.

Ta…
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: K2-K6 on July 24, 2022, 12:31:07 PM
Motul 10 viscosity if available in your marketplace.

Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on July 26, 2022, 12:45:59 PM
Thanks Nige… Agip oil went in as locally available.

At last the rebuild begins, with the engine into the frame today. Am lucky enough to have an electric hoist in my garage roof - worth its weight with the Moto Guzzi rhinoceros thing…
All went smoothly with no dents nor scratches anywhere; my missus is becoming better and better @ such helping chores.

Q - the various fork bolts. (1) how come there aren’t D washers at every clamping joint, and, (2) should you expect the D washers (Fork upper bridge) to be loose or clamped at the 6ft lbs torque book figure. Mine, currently are rattling, though tbh I’ve only done them up guesstimate tight for now.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Oddjob on July 26, 2022, 01:29:10 PM
If the top yoke clamp bolts are 8mm then it's supposed to have D washers and yes they'd not rattle.

The pinch bolts are also supposed to be fitted so the nut is at the lowest point, so back of the yoke, this is so if the nut ever came undone only the nut and spring washer would fall off, if fitted the other way the entire bolt would slide out. Added bonus to doing it this way is that IF the bolt ever slid out it would almost certainly hit the tank, that would most likely dent or at least ding the paintwork due to the weight of the bolt, you may get away with the nut hitting the tank.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on July 26, 2022, 02:03:54 PM
Cheers Ken, interesting and sensible…

Wherever possible, I’m trying to be totally accurate with the rebuild, and what you write is in confliction with my Honda Parts diagram - which shows the bolt inserted from the rear!

Was it a later Bulletin perhaps? Regardless, I may well take your advice on this one; tbh I’ve been slipping in the odd extra washer as can’t bear the thought of raw spring washers against the new & pristine powder coated frame.

(…just had a thought: if a stanchion pinch nut disappears whilst riding I’ll have far bigger problems than a scratched tank to be worrying about 😂)
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Oddjob on July 26, 2022, 02:38:07 PM
That's true. However by putting the nut and spring washer at the bottom it's also visible to you as you ride. So if it was coming lose you'd have at least a chance of spotting it. Other way round and they are slightly hidden and thus first thing you may notice is the bolt missing entirely. The bottom pinch bolt would hold the leg I'd imagine until you got round to fitting a new bolt. Trouble is those bolts are chromed so they tend to be special order etc and not cheap.

If the bolt was the later 7mm bolt there are no D washers fitted to those but a K2 would have the 8mm ones as standard IIRC.

Parts book is fine for seeing correct parts but not for orientation IMO.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: K2-K6 on July 26, 2022, 02:51:32 PM
I can see the logic of fitment opposite to manual but have always done it as illustrated by Honda, never had one come undone on any bike though.

The arrangement they've got may (you'd need to check bore size etc) be such that the placement of the bolt head and restricted by the D washer keeps the alignment of the bolt coming through the front of the casting. That could be to prevent the bolt shaft pulling inward toward the stanchion and maintaining a flat pull on the front of the casting. The front hole can then be "floating" without binding to  give more than desired bend to casting, in other words trying to keep both bolt head and nut faces planar to each other.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: K2-K6 on July 26, 2022, 02:54:47 PM
Similar to front spindle clamp orientation.

The lower triple clamp is also steel and much less vulnerable to excess bolt load than the top aluminium casting, which takes most of the chassis load on it's own.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on July 26, 2022, 10:31:28 PM
Thanks gents.

Nige, slightly struggling with your explanation/ logic as surely a torqued nut/bolt combination will behave as a ‘unit’, though I agree the fastener end planer forces will be higher at the floating end of the casting…
Maybe I’ve the wrong D washers, but certainly they provide no restrictions to the passage or siting of the bolt through the constant bore size….. as I mentioned; they’re currently rattling! (bolts tight but not checked wrt torque value yet)
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on July 27, 2022, 02:22:20 AM
Tips pls on compressing the rear shock springs wrt dismantling the units? Have looked eBay but concerned the jaws of all I see too bulky to engage the lower part of the spring (ie next to the damper)

Have tried 4x decent tie-wraps and ratcheting down… but too much force required methinks.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: K2-K6 on July 27, 2022, 08:16:04 AM
Thanks gents.

Nige, slightly struggling with your explanation/ logic as surely a torqued nut/bolt combination will behave as a ‘unit’, though I agree the fastener end planer forces will be higher at the floating end of the casting…
Maybe I’ve the wrong D washers, but certainly they provide no restrictions to the passage or siting of the bolt through the constant bore size….. as I mentioned; they’re currently rattling! (bolts tight but not checked wrt torque value yet)

 ;D I can understand struggle, my explanation was a bit rambling Simon. I know what I want to say but putting words to it more challenging. 

Another go, essentially it's a compromise joint and so will have different views on deployment as I see it. Ideally the centre of the bolt "wants" to be dissecting the circumference of the fork stanchion to be a best design. Some do actually do that with a relief in the bolt that has to be placed in situ before the stanchion goes in to give correct load line with least possibility of distortion. 
With the honda one here, as you tighten the bolt it wants to banana shape itself away from stanchion centre (pushing the bolt shank inwards toward the stanchion) which the D washer may help prevent.  Also to stop the casting gap closing too much.
Guess they are trying to get workshop to do it up without snapping the casting as the stanchion is all but incompressable. If they've accommodated that with geometry in any way then it's advisable to assemble as the manual. If there's not a convincing reason to deviate then that would be wise.

Just checked an original fit 750 K2 and the D washers are definitely clamped tight when joint is secured.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Oddjob on July 27, 2022, 11:22:41 AM
You may be vastly overstating this, Honda changed the design to a 7mm bolt and ditched the D washer. It appears they were trying to reduce the diameter of the bolt head to a 10mm instead of 12mm so that you couldn't tighten it as much thus breaking the casting. The castings didn't break at the bolt, they broke halfway round the casting, which would point to overtightening. The D washers I think were installed in the first place so that when they went rigid the bolt was tight enough.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on July 27, 2022, 12:53:03 PM
Thanks Nige / Ken; I guess I’ll just stick with the parts manual drawings; if for no other reason than originality.

I’m away from the bike now for a couple of weeks; but do balk at doing the clampings up ‘D washer tight’: yesterday evening I went to my comfort limit wrt what I reckon a M8 Stanchion bolt in an alloy casting should take. (I did though pre-measure the D washers at 2.3mm thickness - maybe there’s an issue here?)

I’ll stick a torque wrench on it later and double check my wrist calibration…

Cheers!
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: taysidedragon on July 27, 2022, 02:41:24 PM
Thanks Nige / Ken; I guess I’ll just stick with the parts manual drawings; if for no other reason than originality.

I’m away from the bike now for a couple of weeks; but do balk at doing the clampings up ‘D washer tight’: yesterday evening I went to my comfort limit wrt what I reckon a M8 Stanchion bolt in an alloy casting should take. (I did though pre-measure the D washers at 2.3mm thickness - maybe there’s an issue here?)

I’ll stick a torque wrench on it later and double check my wrist calibration…

Cheers!

If the nut is tight but the D washer is still loose, the nut, or the head of the bolt must be catching on something else and tightening on that. Maybe part of the yoke casting? Are the bolt head and nut the original sizes across the flats? Any increase in size might cause a problem.  Just a thought.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Seabeowner on July 27, 2022, 06:55:30 PM
Tips pls on compressing the rear shock springs wrt dismantling the units? Have looked eBay but concerned the jaws of all I see too bulky to engage the lower part of the spring (ie next to the damper)

Have tried 4x decent tie-wraps and ratcheting down… but too much force required methinks.
I did the 500 shocks using plenty of ingenuity and a couple of ratchet straps. Fixed the shock upright and fixed the straps to an anchor points either side. You can wind the straps up inside the shroud by a turn.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on July 27, 2022, 09:10:40 PM
Thanks Gareth: pretty certain of no issues other than my reluctance perhaps. I did consider the fresh paint within the yolk; but I did have to Dremel-scotchbrite much of that away simply to get the stanchions through. A bit of me still wonders whether the D washers are undersized?

Seabe.. like the sound of that and will give it a try. Many thanks.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: K2-K6 on July 27, 2022, 10:26:12 PM
Thanks Gareth: pretty certain of no issues other than my reluctance perhaps. I did consider the fresh paint within the yolk; but I did have to Dremel-scotchbrite much of that away simply to get the stanchions through. A bit of me still wonders whether the D washers are undersized?

Seabe.. like the sound of that and will give it a try. Many thanks.

Aah, that may have an impact on the washers, any paint in the bore will push the gap apart where the washer sits.

In manufacturing the bore is made all but identical to the OD of the stanchion and then the cut made. If it's not done in this way then the bore (if too big or small) won't have the same circular shape as the fork leg and not be able to clamp effectively. Any additional coating in there will give error.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Oddjob on July 28, 2022, 01:58:10 PM
I seem to recall the D washers are 2.3mm thick as standard so it doesn't sound like that's the problem.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: K2-K6 on July 28, 2022, 02:55:49 PM
You may be vastly overstating this,

You're probably right Ken, but while the world and his dog concern themselves with, variously, meltdown, invasion, no gas supplies, rail strikes etc etc and all other frivolous malarkey,  we can come to the relative peaceful and far more serious subject of discussion as to how the nuts and bolts really should be arranged  ;D

Also via an intercontinental motorcycle forum no less, I'm sure we'll be able to sort it out.   :)
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Nurse Julie on July 28, 2022, 03:19:48 PM
Here is one of our 750/4's
Have you got a Unicorn top yoke fitted Simon?

[attachimg=1]
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on July 28, 2022, 11:48:02 PM
Thanks Julie, unsure what a Unicorn yoke is, but afaik mine is just plain old 1973 Honda. Appreciate the photo. Nothing has changed wrt this area (other than fresh powder coat) and I can’t bloody remember how the D washers were at tear-down.

The stanchions are DSS patterns …. gave Trig the old ‘ uns. (restoring the UK based bike from my work place in Brunei was a problem back then!)

Q1. Wrt the mostly cleaned away paint, should the stanchions be a fairly tight slide in, or easy insertion? Mine are tight, needing a fair amount of pushing and twisting.
Q2 - do you preferably torque them, or use the D washers as an indication of final clamping?

I might be wasting everyone’s time here as not yet put a torque wrench on them, which will happen in a couple of weeks now. Regardless, a big thanks.
Title: Re: 750 K2 Strip & Rebuild - help please
Post by: Lobo on August 13, 2022, 09:35:19 AM
Back from my hols and checked the torque on those 7mm / D washer top yolk today.. were bang on at 8ft lbs. Ie the washers still rattle.
It got me thinking deeper - surely if these washers tighten up you can’t be certain that the stanchion is fully clamped? Are they not provided as a simple yolk-crack saving device?
I’ve cleaned away 80% of the powder coat (more or less bare metal showing) and honestly don’t want to go more. Those washers have about 0.2mm rattle slack - it’ll do me… unless I’m missing something critical here.

Wrt to the rear shocks, they are fully checked, cleaned and as good as new. I never was able to compress the springs enough to access the lock-nut to upper mount, mainly because 50% of said spring is inaccessible under the chrome skirt. 3 stout tie-wraps over 1/2 the spring afforded me just enough to do the job.
With the twin top collars removed I noted the upper mount was about 0.5mm too large to pull through the upper holes in the chrome skirts - at 4 circumferential points - and so ground away a minuscule 0.25 mm notch at each point with the Dremel. (I wish I’d tried heat… the interference was so minimal it might have worked?) The top mount  then pulled though and gave me access to the lock nut / disassembly.

A horrible job due my puny muscles compressing the unit against my  flabby gut - glad it’s bloody done.


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