50 Caliber Racing 60cc Big Bore Top End Rebuild Overhaul Kit For Yamaha Y-zinger Pee Wee PW50 and Yamahopper QT50 Pit Bikes - [4449B] Compete 60cc Big Bore Top End Kit Piston, Rings, Pin, Circlips, Bearing, Gaskets, Studs, Nuts, Spark Plug For Yamaha PW50 Pee Wee 50 Pit Bikes Increase displacement to 60cc - Uses existing cylinder head 50 Caliber Racing - Free USA Shipping