ok i am going to buy a piston kit but i dont know what size to buy. the in side cylinder walls are at 66.57. so what size di i buy? and can i go with a high comprsion piston? if i do do i need to chang any thing on the bike?
You should take it to a dealer and have them measure it and then they will be able to tell you what piston to get. They will also be able to tell you if you need to bore or not. Unless you have the proper tools to measure the cylinder it is almost impossible to tell weather it is worn to far or out of round or tapered. I believe the service limit for piston to cylinder wall clearance is .004" MAX