To keep the flywheel from turning when trying to remove it, I put the handle of a 1/2" ratchet handle under the flywheel and let it wedge itself against the block and that usually works. Sometimes I will take a string and feed it into the sparkplug hole as the piston comes up that will wedge the engine so you can take the flywheel nut off. Don't forget to take the string out afterwards!! Other times I have used a vice grip on the pulley shaft and let it catch on a belt guard or something to hold against while I pull the flywheel nut. Of course this is all shade tree Dave engineering!