"Sick Bike Parts sells a variety of products for use with 2 stroke engine kits, and 4 stroke engine kits and electric bike kits, but does not sell the actual gas motor kits themselves. They invented and sell a shift kit that works with almost every bike, which means you can use the gears on your motorized bike for better pulling power up hills without losing top end speeds."
Website: sickbikeparts.com
Forum Username: @Pablo