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Message: [QUOTE="Rich Rohrich, post: 669539, member: 16241"] I've put together quite a few big bore four-strokes and have [b]NEVER[/b] seen a broken ring. Eric Gorr has put together more big bores than almost anyone and has never seen a broken ring either. It's hardly a common failure. The piston problem you described sounds like a cold seizure which IS common if proper warmup of the forged piston isn't followed. Forged pistons expand more than cast pistons and they have to be warmed up slowly and carefully. If you ran this piston for four months without hurting the intake skirt you can pretty rule out an notions of improper piston/bore clearance on the initial build. Improper warmup, running the engine low on oil or some some foreign material in the bore are the more likely causes for damage to the intake skirt. The cam caps seizing is a common problem with these engines if they aren't assembled correctly. That certainly sounds like the case with your engine. Lots of two-stroke trained mechanics crank down the caps and seize the cam bearing surface. These bikes are remarkably reliable but they can't just be slapped together like our old trusty two-strokes. Proper assembly by a [b]qualified[/b] four-stroke mechanic is one of the real speed secrets of thumpers. [/QUOTE]