I have a used 1996 XR600 I recently purchased that runs quite well. Starts fairly easily. Has a fairly loud ticking, clanking, type noise when cold. Seems to be coming from the front of the engine, but could be coming from the side. After the bike warms up, the noise is hardly noticeable. It is still there and seems to go up and down with the revs. Could this be the exhaust gaskets if someone tried to re-use them? Do they seal better when the engine gets warmer? These are crushable copper correct? Someone else told me it might be the cam chain, but if that was a problem why would it get quieter when the engine is warmed up? Thanks for all your help.