Engine Clunking

Hey, I have an 86 fz600, same aircooled engine as an XJ600, and it has an intermittant clunking at idle (seemed to be coming from the bottom end, stethyscoped it but just heard the usual whirring everywhere, quite loud and sounds like something banging around).
Bike revved smoothly and had no problems but the clunking was quiet loud so I pulled the engine and now have it apart. Thing is though it looks damned good inside, transmission and everything. One thing I thought was that the cam chain might be near the end of it's life (35,000km on the engine) and it could be making the noise.
Anyone know what the tolerances on it should be? Or if this noise is a common problem with this engine (caused by something else besides the cam chain)?
thanks for the help

 

Common problem with XJ engines is noise from the primary chajn to the starter clutch. Always prominent at idle as they have an oil pressure driven tensioner.

At idle there is not enough oil pressure to take up the slack so the chain rattles around a bit.


Damn expensive to replace though but worth considering if you have the engine apart. Do the cam chain while your at it. Nothing like peice of mind that things are new.

 

Check your header pipes with the stethoscope. These bikes have dual wall pipes and when the inner wall breaks loose it can make some noise.

 

Thank You!! Goon
your answer sez all I needed to know, V much appreciated.
Uhhh.. My.. Moto has single wall pipes. can't honestly say I've seen one with double walls.. ever .