Motorcycle Repair: 1977 Honda CB750 K7 - Primary chain, 1977 honda cb750, cam chain

Question
Hi Rich,
I recently purchased the bike above and then had some minor engine work done - points, tensioner, new front tire, carbs synced, alternator cover gasket replaced due to a minor leak. There was (and is still) a pronounced rattle at low (1200 and below) rpms. The mechanic told me after checking into it that the noise was coming from the primary chain, not the cam chain as originally suspected (turns out the cam chain was okay). He further indicated that the problem with the primary chain was not severe and did not need attention (rattle disappears above 1200 rpms and even more once the engine is warmed up).  The bike has 31K miles and I really don't have any other maintenance history on it. My understanding is that replacing a primary chain means "splitting the case" - taking the engine apart.  I would love to get the bike to idle quietly (no rattles) at 1000 rpm, but apparently this can't happen until the primary chain has been replaced. At what point and with what symptoms will I know the time has come for this major repair? Thanks in advance for your answer.

Answer
John, your mechanic told you correctly,  I think you will find out if you pull the clutch in the noise will get much quieter.  I wouldn't worry about it if it were my bike.  I've tried on more than one occasion to find and eliminate that clutch rattle without success.  If you pull it apart, more than likely you will not find anything that needs replacing.

Regards
Rich