I'd read that, dudes make no sense. 1mm is .040" so having the piston .040" further down the hole is not going to make it run off the exhaust port, the piston will be further on the port. I haven't measured the length of the KX piston yet. I'd better hold out until i yank these motors apart tommorrow night and see whats up. i have both versions of the CR500 rod in stock so we'll see how it goes.