I have been reading Gordon Jennings' Two Stroke Tuners' Handbook. It's quite a piece of work. The stuff he covers in the first chapter (which he considers "basics") is all new to me. I guess my HiTorque two stroke education was not quite complete... Here's the question: Jennings states that maximum engine speed is determined by piston speed. He states that (if I remember correctly) the max (average) speed is 4000 ft/sec. He gives a formula to find average piston speed. ---What is the factor that determines this limit? Lubrication (which improves with technology), inertia (which is actually accelleration - not speed), some physical material property of the piston or cylinder, or something else entirely???? ---Why would this be a factor of average speed and not maximum speed? I would have guessed that the maximum engine speed would be determined by inertia. In other words, the weight of the parts that reciprocate would want to be low to minimize the forces from accellerations but would want to be heavy to be strong enough to withstand the accellerations, but that would increase the accelleration loads - and so on and so on...... The optimal solution is never obvious.