Cheap and almost instant piston stop: 1, old proper spark plug. 2, one long bolt. 3, break the center ceramic out of the spark plug.4, tap the shell inside to fit the long bolt. 5, screw the bolt into the shell with the head where the spark gap used to be. 6, cut a slot in the bolt for a screwdriver. &, install, turn the engine to what you think is TDC. 7, turn the engine backwards to the stop. That is it.TDC is right between those stops.
