Universal Parts QMB139 Cylinder & Head Kit | 39/47/50mm

Complete cylinder and head kit for QMB139 4-stroke 50cc engines. Choose from 39mm (stock), 47mm (72cc upgrade), or 50mm (81.3cc upgrade) bore from the drop-down. Includes everything needed for a full top-end rebuild. Note: larger bore sizes may require engine case modification.Kit includes: complete cylinder head, cylinder, piston, rings, piston pin, circlips, head gasket, and base gasket.

• Cylinder bore: 39mm (stock) / 47mm (72cc) / 50mm (81.3cc) — select at checkout
• Cylinder sleeve OD: 45mm (39mm bore) / 52.8mm (47mm bore) / 53.95mm (50mm bore)
• Wrist pin diameter: 13mm
• Total piston height: 34.4mm
• Compression height (wrist pin center to piston top): 17.25mm
• Intake and exhaust valve length: 64mm
• Non-emissions head
• Weight: 4.75–5 lbs (varies by bore)

Compatible Engine:

• QMB139 (139QMB) 49cc / 50cc 4-stroke
• Genuine Buddy 50, RoughHouse 50, Rattler 50, and other QMB139-powered scooters

Note: Larger bore sizes (47mm and 50mm) may require modification to the engine case to accommodate the larger cylinder.For off-road and closed-course competition use only. Not intended for use on public roads.California Prop 65 Warning: www.p65warnings.ca.gov

• Complete top-end kit — head, cylinder, piston, rings, pin, circlips, head & base gaskets
• Three bore options: 39mm (stock) / 47mm (72cc) / 50mm (81.3cc)
• 64mm intake and exhaust valves — non-emissions head
• 13mm wrist pin, 34.4mm piston height, 17.25mm compression height
• Fits all QMB139 (139QMB) 49/50cc 4-stroke engines

Bore Options: 39mm / 47mm / 50mm | Sleeve OD: 45mm / 52.8mm / 53.95mm | Wrist Pin: 13mm | Piston Height: 34.4mm | Compression Height: 17.25mm | Valve Length: 64mm | Head: Non-Emissions | Weight: 4.75-5 lbs | SKU: 151-242

QMB139 (139QMB) 49/50cc 4T | Genuine Buddy 50 / RoughHouse 50 / Rattler 50 | All QMB139-powered scooters