Originally Posted by
22Racer
I am not sure why people say you can't balance a single cylinder engine.
Because you can't. The perfect "balance" changes depending on crank position, rpm, etc. Multi cylinder engines compensate for this automatically (well some do). As one piston is going up, another is going down and the changes mostly even out.
You actually would NOT want to match counter weight to piston/rod weight. It would vibrate like crazy at high rpms.