I've done a little research but i don't know a lot about motorized bicycles. so forgive me if i am lacking important details and don't know the terminology. i saw a bike for sale and called the number to get the details....its a 26 inch mountain bike with a gas engine mounted above the rear tire. supposedly it does 30-35 mph, i'm not 100 percent but i think it was around 50 cc... with a separate 2 liter gas cell and i believe there is a tank on the engine too. the guy said something about a centripetal clutch or something i don't know what that is. anyways to make a long story short he wants 400 and i think i can haggle him down to 300-350, sound reasonable/ good deal?