SOHC.co.uk Forums > CB350/400

Looking down the Cam chain tunnel

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mike the bike:
It might have been caused years ago by a previous owner.   If it sounds ok now don't worry about it.

Laverda Dave:
I have rebuilt four 400 engines over the years and they have all had the same issue as yours does.  As I normally have the engines apart for a rebuild I use a fine file to clean up where the aluminium casting has been turned over by the flapping cam chain.
I've never had a problem with any engines following the rebuild and file surgery although I always install a new cam chain, both tensioner blades and the sprung tensioner horseshoe making sure the tensioner plunger has no markings caused by previous owners over-tightening the tension adjuster.

petermigreen:
Thanks, that's good to know. As said, the mechanism is lovely and free and the chain looks very good. Given that I'm not going to split the engine any further as it is very good with hardly any wear.
Thanks again all. Peter


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Dave_Canada:
Since the two chain tensioner rod springs have lost a lot of "spring" in 30+ years (unavoidable) the factory tensioning procedure won't work now. You need to remove the cap bolt and push on the top of the adjuster actuating rod with a nail or thin screwdriver, listen to the engine running and press down hard enough to just quiet the chain rattle, then tighten the lock bolt. Be very careful around the hot headers, of course! Too much force and it will be quieter but the blades will wear rapidly.
Be extremely gentle with the rod lock bolt: it's a 6mm thread into the engine, not the visible beefy 8mm thread which is only for its locking nut. Breaking these bolts by overtorquing is not unusual and a major PITA to fix.
Some rattling is OK but annoying, chain tension has to be quite loose for it to hit the case.
The adjuster springs 14541-333-020 and 14543-333-020 are NLA, and would require a case split to replace anyway.

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