Clutch Basket End Float question

Old Shep

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Hi
I have just finished rebuilding a 1980 CB750K it runs well but is quite rattly, its had new cam & primary chains. I have replaced the rivets on the clutch basket gear with bolts and there is no slack now. The question i have is how much end float to expect on the when its assembled, there is .053"(1.35mm) on mine.
See attached drawing.
 

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I'm finding it hard to understand why you thought you had to add a shim in there and why you still have clearance, all that should be tight. Is that yellow shim the OEM part?
 
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The yellow part is a 25mm washer part number 90455-333-010 which is shown on my parts cat:- drawing, it was fitted when i got the bike and if this was removed there would be even more end float.
 
Fine, just wondering if a different part was subbed there.

Absolute death if you removed the rubbers completely. Likely the same but a little slower if you simply bolt solid (rivets only removed) to remove the cush drive action there. You do not have enough metal interface there to hold solid bolted solid. Going solid is the worst thing you can do there. Before, the big bosses took all the load, now the puny bolts do as well as that paper thin backplate, serious mistake.

Your extra clearance issue does not compare to that. It likely showed up due to missing rubbers which were thicker or the bolts go too far to squeeze them flat. They take up slight space to minimize the clutch basket and back rivet plate wearing on the gear because the rivets were exact length to allow it.

I wouldn't even crank up on that.
 
I am happy the basket and cush etc, the end float was the same before i modified the basket from rivets to bolts, i did this because the gear was extremely lose and rattling. I do not know the history of the bike the frame number is for a 1979 CB750KZ, the engine number is RC04 220793 only 6 digits, should be 7, assuming that the last digit is missing then its a 1981 CB750FB.
There are gearbox differences between KZ and FB (see attached layouts)
There is a spacer on the mainshaft (item 23) on a FB but not on the KZ.
I think i need to strip the gear to find exactly what i have got.CB750KZ.jpgCB750FB.jpg
 
You simply have the late and early trans pics up, the 'extra' spacer is likely the same one labeled as 19 in the other pic. The trans shaft overall lengths stay the same and have to, to line up with the other shaft. Honda simply added a couple more bushings inside more gears to lower wear issues. Every early DOHC trans from 750-1100 Honda makes will drop into those cases if you get all the pieces located right. The pieces from the bearing in back of clutch forward are the same other than the 1100 clutch pusher.

You can be happy with that modded clutch basket until you run it, I'm telling you bolting down solid there is NOT going to work over the long run. Removing the cush by making it solid puts the major load on the bolts themselves which were not nearly so loaded with the rubber working back and forth. I'm assuming now that you left the rubbers in to take up space at least. That may save you from walking home. There will be no noise at first, but you will get added wear when the aluminum scraping the gear begins to file itself into powder. It may shell bearing in crank and you won't pick up on it. You could have at least helped yourself a bit and loaded the clutch basket in the operational direction to torque the bolts THEN, simply tightening them where they were at may make your issue much worse as you are likely in the middle of the unloaded slack, and you better have worked out how to get either self-locking nuts or loctited parts heavily to keep the bolts from backing nuts (if used) off. The bolts best be ultra high grade as well. You have also stopped the clutch basket from being able to roll slightly out of plane to allow the clutch discs more ability to slip with no snagging with each other. Clutch works smoother as a result.

Did you ever drop the shock plate in the clutch stack? The marcel one with the rivets in it? A good indicator of what your solid bolt setup may do, they come apart while popping the rivets in pieces and the biggest problem with that clutch. You replace that plate with two steels next to each other.

Are you aware there are kits for renewing those rubber bushings that loosen up there?

https://www.ebay.com/itm/Honda-CB75...B1100F-Clutch-Damper-Repair-Kit-/302708195780
 
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FYI, some of your 'clearance' there is mandatory, you have to have it to let the inner clutch hub spin freely from the outer basket or the clutch refuses to work right. I'd look for at least .015" there for sure. When the outer 4 notch nut is torqued up on the hub, the two parts must be able to spin easily separate of each other.

And thinking about it more, none of that 'doom and gloom' above will happen likely. The clutch basket stands the rubbers go over are the distance setters there, not the bolt tightness or length, it simply pulls the backplate up tight. You think you are now tighter there but in the same state you were before, the take apart simply makes you think it's tighter until it works back loose again, like in minutes. Rubber rebuilds can commonly make you think that, they never go back together the same way.

Forgive me for being the idiot there.
 
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Thanks for all your advice. Since i have had the bike i have only reworked the top end and clutch, as i said i will strip the engine and have a look at the transmission taking in your advice. The engine is quite rattly, weather that's coming from the loose clutch basket or not i don't know, i suppose i could start it without the clutch assembly fitted and find out.
 
'i could start it without the clutch assembly fitted and find out.'

Please don't, you will have several major oil leaks with low pressure, you could damage bearings. Clutch parts seal them up.

The primary chain damper can make noise as well as it has the same design type of hub the clutch drive gear does.

One of the biggest causes of excess rattle is not having the carbs perfectly synced to even out the idle, the engine then idles jerky to max rattle all parts. Even a well built engine not synced can do it.
 
Hi, appreciate this post started 2020.
Just completed rebuild of a 1979 CB750KZ RC01E engine, final remaining issue appears to be this clutch rattle. Have replaced to rubber cush drives and needle bearings on clutch basket, this resolved the rotational movement between the gear wheel and clutch basket and reduced the rattle noise and vibration significantly. Clutch was rebuilt as standard but clutch basket has significant end float approaching 1mm. Output shaft has no wear, thrust washer is in place and is standard.
Is there a definitive value for this end float, 1mm appears excessive?
 
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