SOHC.co.uk Forums > CB350/400

Almost finished (I think)

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Dave487:
I tested chain as Hairy suggested (learned from a previous post) but maybe it would have been better to have replaced it anyway. However I still think its the clutch gears not meshing properly and intent to buy another clutch unit complete, de-rivet it and try to replace the cush drive.

mike the bike:
The cush drive inside the clutch is unobtainable.   Ivealready ground off the rivets and looked into replacement rubbers.  The rubbers wouldn't cause a noise like that anyway, don't waste your time.

Dave487:
I'm still concerned about the whining transmission which seems to be getting worse, particularly on overrun. If I pull the clutch and stop the engine the noise changes so I think it's likely to be on the primary drive.
I'm so bothered by it that I've split the cases again to have another look.
There's nothing obvious but a few things may be contributing.

1) The bush on first gear is a bit worn which allows the gear float about and touch the mating one. So I'll replace it.
2) Hi-Vo chain appears to be ok (see photo) but I'll replace it anyway this time.
3) The cush drive rubbers in the primary gear have a bit of slack but are very hard, not sure how soft new ones come but I'll replace them anyway.
4) My main concern are the primary chain guides as these are very hard and worn at the ends particularly the bottom one(see photo) but the chain is not touching the attachment screws. I could make new ones out of Nylon66 or Tufnol but the originals have a metal backing even though they're like a brittle plastic.

Does anyone know what a new one feels like, are they like a neoprene rubber or more like nylon?. I can't a find source of replacements at the moment.

Maybe I'm a bit fussy having never ridden another one, but a bit concerned about something locking up and chucking me down the road.

CBNelly:
Hi everyone
I've just joined the forum and currently have my 400/4 engine in bits
Reason for strip is a whine from the clutch/gearbox when under load in gear
I've seen a few threads and even a Youtube clip with the exact same noise
Has anyone found a reason for this noise yet?
I've quickly checked all my bearings and gears/cogs and all seem fine
Only issue I have is the first gear seems loose on the shaft but not sure what tolerances apply
Any help anyone can give to resolve this noise would be much appreciated!

Dave487:
As I said on the previous post I took it all apart, replaced the primary chain and cush drive rubbers and made a new bush for the first gear pinion, I also managed to source a better bottom primary chain guide and I re-checked all bearing races in the gearbox but couldn't find a noisy one.
 I had previously changed complete clutch for one with less play in the clutch damper but I can't find any replacement damper rubbers at the moment.
 
None of this made a significant improvement to the transmission whine but it did give confidence that I'd done it right the first time. I've done about 400miles since re-assembling it and don't really worry about it anymore although I may take the clutch cover off during the winter have another look at the clutch drive gears (ie. checking for correct meshing etc.) as I still suspect that the noise is somewhere in the clutch drive.

I've dismantled the old clutch by drilling out the rivets but the damper rubbers are an awkward shape to make and really need to be moulded. I was in contact with TTR400 some time ago but he doesn't have any stock now so anyone has a source of supply please let us know.

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