Quote: I suspect, even though it may be impossible to measure that the crank may not be travelling at a constant speed in one revolution as the piston speed changes four times every revolution. everybody agree?
You have the counterweights on the crank doing their part to maintain inertia. The piston may be changing speed as it changes direction but the crank is still rotating in the same direction. With the additional weight of a flywheel on the end of a crank I'd have to disagree and say the speed would be constant.
If your theory were true then it would be a miracle that single cylinder 4 stroke motors run at all.
