I would say cop a new pipe. I like the Simonini Circuit a lot. I ran it on my stock cylinder for a little bit. This will get you more rpm's. You can try your hand at porting also. Shortly after this thread I bought a 70cc Cast Iron Polini kit, and never looked back. I also went to a 52 tooth sprocket in the rear with my stock set up, and I ran a launch lever for when I needed some umph, lol. I hope that helps, and good luck!