just turning the flywheels down in a lathe doesn't remove that much weight (a handful of grams I would guess), a better bet is to take some pliers and bust off the full fins that oppose each other, I leave the base of them (1/32") as to not weaken the support they give. I try to do it as even as possible, they end up coming out close to balanced. I recently got a Dubro balancer to even them out, works pretty good with some work to get the hub to center.

zoom in on the attached image (if it worked, haven't used the new upload thing yet) and you can kinda see what I do on the poulans, would be easier to see if they didn't use backwards flywheels...