mine topped out around 100mph or something in the like, i can barely handle that speed, but if you got the money for it, just get some nice pipes, a racing clutch or bigger carbs, it can be delicate work and not to mention, the price....but you should be able to get going pretty fast, i remember my dad's old '97 mxz 670 hit 120mph!!! i dont know what he did to that thing, but it was a beast on the mountain and the fastest out of the other sledders, and up in Silver Sands there were ALOT of custom sleds, i saw videos of it, scary really, these things were fast, they really knew their stuff