When you crank this thing open, the motor gains revs, and likes to hold the revs, even after you back off the throttle. A leaky manifold was the culprit. I was having so much fun riding it around the track, and it's on-the-gas most of the time anyway - it didn't really bother me. But it's a good way to burn a piston, or worse, wreck. It's fixed now...but I see my Dellorto carb plastic float has a bit of gas sloshing around in it now too - so I ordered a new float.