Punch up bafflectomy or debaffling or modding stock pipes when you get to youtube. Also check out kawiforums.com they have a thread in there about modding the stock pipe.

 

when you're riding a 250, save the money for a bigger bike. if you drill 4 quarter inch holes in the back of the exhaust, you get a bit more hp, and a better sound. drill the 4 holes adjacent to the rivets on the end of the stock can

 

similar to the yami kart setup. But you still need to know your carb setup.