Dynamic balancing can stop secondary vinration - the rocking couple. But with a Commando crank that should not be a problem. When you statically bal;ance a crank - for high revs, balancing 72 % of the reciptocating weight is good. The standard factor for a Commando crank is about 54% - that is good for riding around town using up to about 4000 RPM. THere is no optimum balance factor which suits both circumstances. If you use a high balance factor, your bike might shake ot low revs. If you use a low balance factor, it will vibrate at high revs.
When you fit lighter pistons without changing anything else - it improves the balance factor for faster riding.
Race motors for 650SS and Atlas 750 often use balance factors near 80 % of the reciprocating weight.
One of my mates sent his good Triumph 650 crank to be dynamically balanced. It came back with a bit shaved off one end and was effectively stuffed. Car guys are idiots. They are all experts at it.
To dynamically balance one of our cranks, a couple of weights of the correct mass probably need to be clamped around the big ends. You can weigh the rods and pistons and claculate the needed mass - but how do you make the weights so they are of the correct mass ?
