i have an 84 200x that i'm putting a 2002 xr200r top end on. so far i've had no problems to deal with but i just found out that the head is worn just enough that it allows the cam to move up and down to the point where its become and issue. i've heard about milling the front of the head and rocker cover out and sliding a repair bushing over the cam to fix this problem. only problem is i have no clue where to find something like this. if anyone has heard of this being done or where i can get parts it would be greatly appreciated.