GY6 50cc (139QMB) Crankshaft (16 Tooth)

Replacement Crankshaft for 139QMB Engines

This crankshaft assembly is made for 139QMB engines and includes a 16-tooth oil pump drive. The main bearings come already installed, so it is ready to fit. Keeping this component in good condition matters for engine output and dependability. It is one of the GY6 50cc scooter parts you can swap out to get your scooter running smoothly again.

Compatibility and Function

This crankshaft suits a range of 50cc and 80cc engines, specifically those carrying the 139QMB engine code. Its job is to link the piston to the transmission so power is passed along efficiently. If your engine code includes "QM" or "FM," this crankshaft should match your vehicle.

Construction Details

This crankshaft assembly is built to OEM specifications and has exact dimensions for steady operation. The tapered end uses an M10x1.25 thread, and the spline end uses an M12x1.25 thread. It has 26 splines and a 41.4mm stroke.

Specifications

• Stroke: 41.4mm
• Overall Length: 247mm
• Thread Size (tapered side): M10x1.25
• Thread Size (spline side): M12x1.25
• Bearing Outer Diameter (tapered side): 42mm
• Bearing Outer Diameter (spline side): 47mm
• Number of Splines: 26
• Number of Teeth (oil pump drive gear): 16
• Fits: 139QMB-based 50cc and 80cc engines with 16-tooth oil pump drive (139QMA, 139QMB, 1P39QMB, 1P39QMA-2)

Fitment

Fits:

• 139QMB-based 50cc engines (16-tooth oil pump drive)
• 80cc engines (139QMB-based, 16-tooth oil pump drive)
• Engine codes: 139QMA, 139QMB, 1P39QMB, 1P39QMA-2, YN139QMB, JJ1P39QMB, 139FMA-2, BD1P39QMB, BN139QMB, 147QMD
• Other QMA and QMB models (16-tooth oil pump drive)

How to choose: Check that the oil pump drive gear has 16 teeth and the crankshaft has 26 splines. An engine code containing QM or FM indicates compatibility.

Shop more: GY6 50cc Scooter Parts (139QMB) · GY6 Scooter Parts · Scooter Engines & Engine Parts · Scooter Parts