Gearnut, I probably only have about 100 miles or so on the engine. The reason I'm pushing it is because I have a friend whose dad rides two-stroke dirt bikes, and he said they break in rather quickly. I'm running 32:1 and it runs fine. Dogtown Burner, I might try leaning the mixture a bit, but I'm convinced it's the vibrations foaming up the fuel that's causing the problem. To test it, I went to this back road in Fairfield that hardly anyone uses and opened up the throttle while occasionally glancing at the fuel line. Sure enough, as the engine picked up speed, the fuel started shaking up like crazy in the fuel line and the RPMs stabilized somewhere below what I know the engine is capable of delivering. I only weigh 120 pounds so I know i'm not overwhelming the engine or anything. It has to be the vibrations. Eventually, if I hold WOT long enough, the engine picks up more speed. Should I try mounting the fuel tank on rubber mounts, or should I try something else?