They're pretty finicky, not sure how much modding can be done. I know one guy who removed the air breather tube and said it ran better. After I replaced my regulator and hose due to a small leak, I tightened up the throttle cable so the cable was pulling the throttle to max it out, it was getting too much fuel and I had to dial it back. If I feel like it has lost power, I change the plug and check for oil residue in the carb. I run a CR4HSB which is a "hotter" plug.