best thing to do is look on ebay for a front spocket for your bike ou need either a 15 or 16 tooth sprocket. i have done this to my bike and have got decent speeds of about 50mph. you can also buy a new jet you want either a 75 or 85 jet, just remove the bottom off the carb unscrew the jet and replace with the larger one, they cost around £10 on ebay too.