GY6 50cc (139QMB) Cylinder Kit 4T (81cc, Iron, 50mm)

GY6 50cc Cylinder Kit for 4-Stroke Scooters

This cylinder kit suits the GY6 50cc (139QMB) and has a 50mm bore, built for 4-stroke scooters. Fitted to the engine, it raises displacement to 81cc and noticeably boosts performance. It belongs to our range of GY6 50cc scooter parts that can change how your scooter rides. For the best outcome, pair it with a compatible big valve head and a performance camshaft.

Performance Boost

This cast iron cylinder kit is an effective upgrade for GY6 50/139QMB engines. It bolts straight on in place of the original cylinder, so it is a simple option for anyone wanting more speed and acceleration. With additional performance parts fitted, riders can expect top speeds of roughly 50-55 MPH.

Recommended Upgrades

To get the most power, fit part number 1100-1239, a 50mm big valve head, since stock heads may not be compatible. The 1100-1250 performance camshaft is another worthwhile addition that works with the cylinder kit to help you make the most of your scooter.

Specifications

• Material: Cast Iron
• Size: 50mm Bore
• Position: Cylinder Kit
• Fits: CSC Go Max with the 139QMB 50cc four-stroke engine (converted from 50cc to 81cc)

Fitment

Fits:

• CSC Go Max (139QMB 50cc four-stroke, 50mm bore)

How to choose: Only use this kit on a 139QMB / QMB139 (GY6 50) four-stroke engine that is still in its original 50cc configuration.

Where it goes: It is part #13 on the cylinder crankshaft diagram for the CSC Go Max.

Other versions: For the 88cc 52mm big bore kit for GY6 50 139QMB, see 88cc Big Bore Kit (52mm) - 50cc (139QMB) / GY6 50. For the 72cc kit with head and 64mm valves for the 139QMB, see GY6 50cc (139QMB) Big Bore Kit with Head 4T (72cc, 64mm Valves).

Shop more: GY6 50cc Scooter Parts (139QMB) · GY6 Scooter Parts · Scooter Big Bore & Cylinder Kits · Scooter Parts