same thing with Harrier 3d and Evo 100, I called Evo tech and they suggested using an idle bar plug or a hotter plug to keep the droplets of fuel from landing directly on the plug element. Long story short this helped but did not run the way I wanted it to until I broke down and mounted it sideways with the tank lined up with the carburetor. ONLY WAY TO DO IT... without spending money on regulators, etc... Buy a different muffler if you need to but I wouldnt fight the inverted glow two stroke ever again Hope this helps