SSP-G 44mm Stroker Crankshaft - QMB139

This SSP-G 44mm stroker crankshaft assembly is the foundation for a longer-stroke performance build based on a QMB139 / 139QMB 49–50cc four-stroke scooter engine. The assembly includes the connecting rod and main bearings, with a splined drive end and tapered ignition-side end. Its 44 mm stroke lets you build around a longer piston travel; final displacement and performance depend on the cylinder bore and the rest of the engine combination.

Key Features

• 44 mm stroker configuration: Designed for a coordinated longer-stroke QMB139 performance build, not a like-for-like stock crank replacement.
• Assembled crankshaft: Supplied with connecting rod and main bearings.
• 26-spline drive end: Match the drive interface to the components used in your build.
• Specified oil-pump pairing: The 16-tooth oil-pump drive gear requires a matching 33-tooth oil pump.
• Detailed fit-check measurements: Shaft threads, bearing diameters, and connecting-rod bore are specified below.

Technical Specifications

• Brand: SSP-G
• Part number: 169-239
• Part type: Stroker crankshaft assembly
• Engine platform: QMB139 / 139QMB 49–50cc four-stroke
• Stroke: 44 mm
• Overall length: 247 mm
• Tapered-side thread: M10 × 1.25
• Spline-side thread: M12 × 1.25
• Tapered-side bearing outer diameter: 42 mm
• Spline-side bearing outer diameter: 47 mm
• Drive splines: 26
• Connecting-rod inner diameter: 13 mm
• Oil-pump drive gear: 16 teeth; use with a matching 33-tooth oil pump

Compatibility

For compatible QMB139 / 139QMB 49–50cc four-stroke scooter engines configured for a 44 mm stroker crankshaft. The 49–50cc designation identifies the starting engine platform, not the displacement of the finished stroker build.

Before assembly, verify crankcase clearance, bearing seats, drive interfaces, and the complete piston/cylinder combination. Piston deck height, valve clearance, cam-chain arrangement, and oil-pump compatibility must suit the longer stroke. Do not assume a stock cylinder and piston will work unchanged. Engine assembly and clearance checks should be performed by an experienced engine builder.

This product is intended for off-road use only. This product is not intended for use on public roads or land.

• 44mm stroke for coordinated QMB139 stroker builds
• Assembled crankshaft with connecting rod and main bearings
• 26-spline drive end
• 16-tooth oil-pump drive requires matching 33-tooth oil pump
• Off-road use only

Brand: SSP-G; Part number: 169-239; Platform: QMB139 / 139QMB 49–50cc four-stroke; Stroke: 44mm; Overall length: 247mm; Tapered-side thread: M10x1.25; Spline-side thread: M12x1.25; Tapered-side bearing OD: 42mm; Spline-side bearing OD: 47mm; Drive splines: 26; Connecting-rod ID: 13mm; Oil-pump drive: 16 teeth, use with matching 33T oil pump; Use: Off-road only

Compatible QMB139 / 139QMB 49–50cc four-stroke scooter engine platforms configured for 44mm stroke; verify crankcase, piston/cylinder, cam-chain, bearing and drive compatibility; requires matching 33-tooth oil pump