Description Our 172cc Big Bore engine kit increases the 150cc GY6 engine bore size from 150cc to 172cc, enhancing performance for a better ride. Use this 172cc scooter cylinder kit to increase the low-end acceleration as well as your scooter’s top speed. This kit includes the piston, cylinder, rings, gaskets, and more. Acceleration and top speed are two primary attributes of a GY6 powered motor scooter that dedicated street-scooterists demand, and the bigger the bore, the better the scooter’s performance. Note: The 61 mm bore size is common to most Chinese-made 150cc GY6 horizontal engines. Some engines may require reaming. Specifications Displacement 172cc Bore diameter: 61 mm