Has anyone tried swapping cams? The ATC200X looks more radical and fits right in. There's a guy in England that has done some research into the XR200 and what swaps. Check out www-staff.lboro.ac.uk/~elvpc/papers/XR200.html for more.
I know where to get my hands on an 83 XR350R fairly cheap because it smokes off and on and has high crankcase pressure to the point it blew out the seal on the clutch side of the engine. Easy fix or major tear down?