Naraku
Naraku 139QMB / GY6 50cc Super Transmission Kit
Description
Restore lost top speed, eliminate off-the-line bogging, and completely refresh your drivetrain with the Naraku Super Transmission Kit. Engineered specifically for 50cc and 49cc GY6 50 / 139QMB 4-stroke engines, this all-in-one CVT tuning package replaces your entire worn factory transmission setup. By matching a high-performance variator, precision-balanced clutch assembly, heavy-duty clutch bell, and a calibrated drive belt, Naraku delivers seamless linear shifting, crisp throttle response, and maximum power transfer to the rear wheel.
What's Included in the Box
- Performance Variator & Drive Face: Optimized roller ramp angles maximize belt travel for improved acceleration and high-end speed. Includes a 26-spline drive face.
- Pre-Assembled Clutch & Torque Spring Base: Features durable, high-friction clutch shoes and an anti-slip torque spring base to ensure positive engagement under load.
- Heavy-Duty Clutch Bell: Precision-vented steel clutch drum designed for rapid heat dissipation, preventing thermal glazing and clutch chatter.
- Premium V-Belt: High-tensile drive belt selected for optimal dimensional stability and minimal stretching under high thermal strain.
Comprehensive Case Length & Fitment Guide
GY6 50cc engines come in three distinct case lengths. Use the drop-down menu to select the correct kit configuration for your scooter platform:
| Belt Option | Engine Case Profile | Common Vehicle Applications & Notes |
|---|---|---|
| 669mm Kit | Short Case (10" Rear Wheel) | Fits standard short-case GY6 50cc scooters running small 10-inch rear wheels (e.g., ATM50-A1, VIP, and classic city scooters). |
| 729mm Kit | Long Case (12" or 13" Rear Wheel) | Fits standard long-case GY6 50cc scooters running larger 12 or 13-inch wheels. Always verify your case measurement matches a long configuration. |
| 788mm Kit | Extra-Long Case (Fat-Tire / Custom) | Engineered for extended-case variants, most notably found on the Icebear Maddog 50cc and similar Honda Ruckus clone platforms. |
Technical Specifications
- Engine Compatibility: GY6 50cc / 49cc 139QMB / QMB139 4-Stroke
- Roller Weight Size: 16mm x 13mm (6g weights included)
- Variator Outer Diameter: 88mm
- Drive Face: 26 Splines | 13mm Inner Diameter | 113.7mm Outer Diameter
- Clutch Drum: 22 Splines | 11.10mm Inner Diameter
- Sliding Torque Spring Base: 118mm Outer Diameter
- Manufacturer: Naraku (Germany)
Tuning Note: The included 6g roller weights provide an excellent balanced starting point for stock or lightly modified 50cc engines. If you have an 80cc Big Bore Kit installed, experiment with heavier or lighter weights to match your modified torque curve.
Installation Tip: Clean the crankshaft splines carefully before installing new components. Never use an impact gun to tighten the variator or clutch nuts without a holding tool — improper torque can strip crank threads or crush components.
About Naraku
Naraku is a German performance brand specializing in high-quality CVT and engine components for small-displacement scooters and mopeds. Known for tight manufacturing tolerances and rigorous quality control, Naraku parts are a trusted upgrade over OEM for riders who demand more from their 50cc platform.
SKU: 137-1 | Vendor: Naraku | Category: Engine & Transmission / Complete CVT Kits
Product Diagrams
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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.
