I was speaking of actually balancing the engine internally. I lost the link, but someone here in the forum posted a link on how to balance an engine. It is not all that hard, but does of course involve disassembling the engine.

Another thought is that if you are using magneto ignition, balancing the flywheel will help a lot. I was somewhat surprised at how much smoother a friend's engine ran after I balanced the magneto flywheel for him.

But once again, if your shaking is most noticeable at idle, the idle mixture is probably too rich. It sometimes is a fine line between a clean, two stroking idle and getting a good transition. If the engine is too rich at idle, it will "four stroke" intermittently, and shake so hard you think the tailfeathers are going to fall off!

AV8TOR