SOHC.co.uk Forums > CB350/400

Almost finished (I think)

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Dave487:
Got the 400-4 on the road and passed the MOT last week. It seems to run ok but has a lot of transmission noise on both acceleration and overrun. I haven't ridden another one so don't know how they normally sound. The noise is not there when running in neutral but it sounds a bit clunky if I unscrew and remove the oil filler whilst it's running. Still quiet if I engage first gear but the noise starts when I feed in the clutch even before starting to move off. It sound like it could be from the clutch / primary gears and there was a bit play in the cush drive when I assembled it. I have a feeling it might be the primary gears not meshing correctly. Does anyone know where I can get new cush rubbers from. I have tried to contact ttr400 but did not get a reply.

hairygit:
The primary "gear" is actually part of the crankshaft on a 400 four, and is not replaceable on it's own, new or replacement crank is the only answer if it is damaged. That said, I have NEVER seen a primary sprocket on one actually damaged. Have you balanced the carbs properly, as all the SOHC fours clatter horribly if they are out of sync. What have you done to the engine, or did you just get it going without stripping it? The primary chain can make horrendous noises if worn, but my money is on the carbs being out.

mike the bike:
Although it's always worth synchronising the carbs, a thought occurred to me;  does it still make this noise with engine off, just rolling down the hill?

Dave487:
Thanks for the replies Hairy and Mike.
Yes the engine and gearbox has been stripped and checked but the primary chain looked ok so was not replaced and the carbs have been synchronised to less than 1 inch Hg.
 The noise I'm worried about is more of a whining noise (I didn't make that clear originally) like 2 gears not meshing correctly and i think it's coming from the clutch side.
The clunky sound at idle may well be primary chain noise but I don't think that's anything to be concerned about at this stage.

I haven't tried running it downhill without the engine running as Mike suggests but will at next opportunity that's a very good point.

hairygit:
Clutch release bearing grinding/whirring is a possible cause of the noise. How did you determine that the primary chain was okay? The basic test is to lay it on a table or other flat surface, and if any links from the top run touch the bottom run, replace it. Generally I insist on replacing it anyway if splitting cases on any Honda four, just because of the hassle of doing it twice hoping to save a few quid! If people moan about it I tell them to find someone else to do it!

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