The Naraku Heavy Duty Crankshaft (SKU 137-78, MPN NK100.81) is a premium OEM-quality replacement for 50cc 4-stroke QMB139 engines. Shown with the Naraku retail box � built to Japanese and Taiwanese OEM standards with a fully machined crankshaft assembly: central flywheel/crankpin with pre-pressed heavy-duty bearings, forged steel connecting rod with wrist pin eye, dual-end main shafts with splined PTO end and threaded timing/stator end, and a visible 16-tooth oil pump drive gear. Matches original crank dimensions for a direct drop-in fit in standard and Big Bore builds. Verify your engine uses a 16-tooth oil pump drive gear before ordering.
Note: Confirm your engine uses a 16-tooth oil pump drive gear before ordering.
Intended for off-road and racing use only. Not intended for use on public roads.
