ORIGINAL: tkg
There is no % vs rpm formula, You just have to try and see what happens.
2 thoughts MOST engines have a heavy piston and need more counter weight. A cheap trick is to clamp on 2 hose clamps around the prophub with the tighten screws inline with the counter weight. You run the engine and see what happens. If you equally twist the clamps in opposite directions a bit at a time you will reduce the effective amount of the weight.
This is an easy way to tell if your engine is heavy on the piston or counter weight.
I have an Alpina 330 that was marketed by Bill Bennett a few years ago. It has on the shaft just behing the prop driver an adjustable weight that is clamped on the shaft. I have not tried to adjust it, but it must serve the same function as the hose clamps you refer to.
I am thinking to convert this engine to ECDI and remove the flywheel and the spring starter to reduce weight. Will tthis affect the position of the adjustable weight? Tnanks.
Sincerely, Richard