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with everthing else OK, the part that I find will hold up starting is the fit of the piston in it's bore, and now days i seem to get that fairly right, I used to make the fit too close, and it took a bit of running in to get it free enough to over cme friction, then a few hours running with heat to get full power, but once up to full power there is little or no wear to the bore or piston for the life of the motor. Friction is the killer of these motors, followed by air leaks.Ian S C
After lapping the cylinder, I lap the piston out of the cylinder until it just fits the cylinder..........