50cc QMB139 4-stroke Cylinder and Head Kit. Choose from 39mm, 47mm or 50mm bore in the Drop Down Box.
47mm Bore Upgrades your Scooter to 72cc!
50mm Bore Upgrades your Scooter to 81.3cc!
Kit includes complete cylinder head, cylinder, piston, rings, piston pin, cir clips, head gasket, and base gasket.
Please see our Warranty & Returns Policy.
*You may need to modify your engine case to accommodate the larger cylinder.
- Cylinder Bore: Choose from 39mm, 47mm or 50mm
- Cylinder Sleeve Outer Diameter: 45mm (39mm bore) / 52.8mm (47mm bore) / 53.95mm (50mm bore)
- Wrist Pin Diameter: 13mm
- Total Piston Height: 34.4mm
- Compression Height (from center of wrist pin hole to top edge of piston): 17.25mm
- Intake and Exhaust Valve Length: 64mm
- Non-Emissions Head