Originally Posted by fdjizm

The crankshaft in a one cylinder engine has always been a debate, myself I don't think it's possible I believe the weight is there to move the resonance frequency higher to get higher rpm's when metal inside an engine starts resonating it's hard to get past that vibration point and get speed.

Heavier/denser resonates much later = no vibration barrier to compete with.
Most high end crankshafts are lighter, but the slugs in the counter weights are denser.

But that's just an educated guess

Originally Posted by RayJ

Most balance weights added are tungsten which is much heavier than steel. The above comment is spot on, and the resonation point would be much higher with a heavier bottom end.