take a look at the hole in the middle of the flywheel. on some this hole is machined with a keyway but on some the key and hole are simply cast in place and getting the little cones of the balance shaft to seat dead center is just about impossible. even with the machined hole the cones will come out off center if the face and back of the flywheel have any imperfections.

long ago when i did a couple of ryobis i just took the fins down by an equal amount all the way around and bolted it back together.


dave