How fast will a 300ex go with a fmf exaust

 

stock is somewhat around 50 - 55 mph so your right around there. aftermarked exhausts and the like wont make your top speed any faster. only 1 or 2 mph faster. you need to change your gearing or get a higher rev cdi box to get a higher top speed (or bigger diameter tires). getting to your top speed is a whole different thing though.