Adjustable Sheave Rear Clutch Pulley - 50cc (139QMB) GY6 50cc

Adjustable Sheave Rear Clutch Pulley for 50cc GY6 Engines

This rear clutch pulley with an adjustable sheave is built for 50cc GY6 engines, with the 139QMB model as the main target. It plays an important role in how your scooter performs. It is one of the GY6 50cc scooter parts that can noticeably improve acceleration and top speed. It also helps manage torque, which makes it a good choice for off-road use.

Torque Control and Acceleration

The clutch seat has an outer diameter of 118mm, so it sits securely on the engine. A pulley needle bearing (HK172518RS) and a torque driver bearing (6901RS, 12mm inner diameter) are included. The ramp grooves are split into three straight grooves for quicker starts and three curved grooves for reaching higher speeds.

What Comes in the Box

The package contains the full sheave assembly, a torque driver collar, an adapter bushing, and a hex nut, so you have everything needed to fit it. Use the correct tools and follow standard installation steps to get the best results.

Specifications

• Clutch Seat Outer Diameter: 118mm
• Pulley Needle Bearing: HK172518RS
• Torque Driver Bearing: 6901RS (12mm inner diameter)
• Ramp Grooves: 6 total (3 straight + 3 curved)
• Includes: Sheave assembly, torque driver collar, adapter bushing, hex nut
• Fits: GY6 50cc engines (139QMB and related QMA/QMB codes) and 50-100cc GY6 engines

Fitment

Compatible with:

• GY6 139QMB 50cc engine
• GY6 139QMA, 1P39QMB, 1P39QMA-2, YN139QMB, JJ1P39QMB, 139FMA-2, BD1P39QMB, BN139QMB and 147QMD engines
• Other GY6 50-100cc engines with QM or FM in the engine code

How to choose: Compare your engine code with the list above. A 50-100cc engine code that contains "QM" or "FM" is likely to be compatible.

Shop more: GY6 50cc Scooter Parts (139QMB) · GY6 Scooter Parts · Scooter Variators & Roller Weights · Scooter Clutches & Clutch Springs · Scooter Parts