Sorry for the non kawasaki question here but there is a shitload of pretty cluey people on here so its worth a shot.
A friend just bought a damaged GSXR600 (03) for a track bike.
It all seemed ok but after its been idling for a while it gets a very bad sounding rattle/grinding noise coming out of the left side of the motor (Gear lever side). if you put your hand against that engine cover you can actually feel it.
once you put it in gear and ride it a little it seems to go away.
as its not registered we cant really ride it that far to really test it to see if it comes back.
I know this kind of stuff is pretty damn hard to diagnose over the net but i was hoping someone may have experienced something similar or could offer some advice on what to trouble shoot to eliminate different problems.