Hi Jeff, always works for me but I don't really use a mash hammer on the underside, I have a piece of RSJ that I sit the boss on and then give it a good wack, but not everybody has a piece of RSJ kicking around. If you can sit the mash hammer on a brick or something solid on the concrete and then hit it, it will come off. I doubt you would break the flywheel as it is completely supported inside the boss and the shaft
