Purchasing a 36 tooth sprocket or lower will increase speed by alot if you live on relitively flat ground. For hills you want above a 44 tooth sprocket. If you port your intake and exhaust you will notcie a dramict increase as well. if you wanna learn about that find the thread on one of the moterized bike forums. i havent done that to mine, A Boost Bottle should increase your speed a couple MPH if not more.( varies with engines ) and your torque ( make your you get the right size ). Cns carb might have better increase in top performance. i dont remeber with mine. and last but not least an expansion chamber, this should increase performance greatly. they can be purchased at sick bike parts.