Naraku
Naraku Heavy Duty Crankshaft 16 Tooth | 139QMB Engines
Description
The Naraku Heavy Duty Crankshaft is a premium OEM-quality replacement for 50cc 4-stroke QMB139 engines. Built to Japanese and Taiwanese OEM standards, it features heavy-duty pre-pressed bearings for extended service life and durability — a significant step up from low-cost Chinese alternatives. Matches the original crank dimensions for a direct drop-in fit, and works equally well as a standard replacement or as the foundation for a Big Bore build. Verify your engine uses a 16-tooth oil pump drive gear before ordering.
Key Features
- OEM-quality construction to Japanese and Taiwanese standards
- Heavy-duty bearings pre-pressed for longer service life
- 16-tooth oil pump drive gear
- Direct OEM-dimension replacement — fits standard and Big Bore builds
- Pre-assembled and ready to install
- Made in Taiwan by Naraku (MPN: NK100.81)
Specifications
- Engine Compatibility: QMB139 50cc / 49cc 4-stroke
- Oil Pump Drive Gear: 16 tooth
- MPN: NK100.81
- Includes: Pre-pressed heavy-duty bearings
- Dimensions: 11" L x 5" W x 4" H
Compatibility
| Engine | Displacement | Type |
|---|---|---|
| 139QMB | 49cc / 50cc | 4-stroke horizontal |
Note: Confirm your engine uses a 16-tooth oil pump drive gear before ordering.
This product is intended for off-road and racing use only. Not intended for use on public roads.
Product Diagrams
Features
Specifications
Engine: QMB139 49/50cc 4-stroke | Oil Pump Gear: 16 tooth | MPN: NK100.81 | Includes: Pre-pressed heavy-duty bearings | Dimensions: 11" L x 5" W x 4" H
Model Fitments
QMB139 49cc/50cc 4-stroke horizontal engine
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Same day shipping for orders placed before 2PM (CST) M-F
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30-day return period on eligible items
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Flat-rate shipping for orders shipped to the 48 Contiguous United States.
