I have a 1991 xlh 1200. The noise sounds like it's coming from the top end. Kind of like a knocking, rattling noise which is most noticeable at idle. The sound does not increase in speed or get louder when reving. Exhaust sounds fine. I have no loss of performance. Good oil level. I took it to a Harley mechanic and he listened with a stethoscope and couldn't figure it out. He said it isn't a rod, piston, or bearing, but something is definitely loose. The only way to figure this out he said was to continue to ride and if the noise gets louder, bring it in. Anyone ever experience a noise which didn't come from the typical engine problems?

Thanks for your reply.

 

Check to see if it is your gas cap rattling. when it is making the noise, put your hand on the cap and see if it stops.