Put pistons and rings in the old mountain cat 800 carb. Power valve had nicked a piston on one side. Anyway, shimmed the power valves with a thin washer that fit over the shaft, put in new suzuki pistons and rings. Fired it up and it ran away. Turned off the key, kept screaming, hit the kill switch, kept screaming, pulled off the plug wires, kept screaming. Finally unscrewed a spark plug and got it to stop. Verified kill switch and key were working, tried again, same thing. What do I got going on here? I drove this sled into that garage, missing a little bit, thought it would be an easy fix, but don't dare put a belt on it if I can't get it to shut down.