50cc 4-Stroke GY6 139QMB gas scooter engine with automatic CVT transmission. Our complete GY6 engine includes electric starter, kick start, and CVT. This engine is for use with scooters with rear drum brakes. Sorry, brake shoes are not included. PLEASE NOTE: There are many different versions of 50cc GY6 style 4-stroke engines used in the Chinese scooter market. This scooter engine is designed specifically for use with 10 diameter rear rims. This corresponds to a tire size of 2.75-10 through 3.50-10. Please be sure your rear tire diameter falls within the range of these sizes. Style: Shortcase Engine type: Single Cylinder 4-Stroke Cooling: Air Cooled Displacement: 49cc Bore & Stroke(mm): 39 X 41.5 Max Power (kw/rpm): 2.3/7500 Max Torque (N-m/rpm): 3.2/6500 Min Unload Stable Rotation (rpm): 1600 +/- 100 Starting: Electric/kick Please choose carefully! Scooterworks now has a firm no return policy on engines, barring manufacture defects or shipping damage.