Sometimes, if the lean condition is JUST right, your engine can run away on you. It'll increase the RPM to like 8000 and you won't be able to shut it off w/ the button or pulling plug wires. The best way to stop this is to open the throttle. This floods it with cool air and stops the auto-ignition process. Press the Stop switch too, as this will kill your ignition, or it'll just start right back up. First time that happened to me, I 'bout crapped myself. Ski was not hooked up to a hose, and I had no idea what to do. Pulled plug wires, no effect, ripped the fuel hose off, no effect (right away), then slowly, after like 30 seconds, it consumed all the fuel in the carbs and finally quit. I thought it was going to blow up!