Universal Parts CVT Torque Spring | 139QMB 50cc

Restore proper CVT engagement and shift behavior on your 50cc scooter with this Universal Parts replacement torque spring for 139QMB 4-stroke engines. The torque spring sits inside the rear driven pulley (clutch side) of the CVT and controls the rate at which the belt rides up the pulley faces as engine load increases. A worn or fatigued spring causes sluggish acceleration, belt slip, and poor top-speed engagement — replacing it restores factory CVT performance.

• 139QMB Fitment: Designed for the 50cc 4-stroke QMB139 engine platform used across a wide range of Chinese-made scooters
• 97mm Overall Length: Matches OEM torque spring length for compatible driven pulleys — verify against your existing spring before ordering
• 57mm Width: Outer coil diameter matches the driven pulley spring seat on compatible QMB139 CVT assemblies
• Conical Compression Design: Tapered coil profile provides progressive spring rate for smooth CVT engagement across the RPM range
• Steel Construction: Dark oxide-coated steel wire for corrosion resistance in the CVT housing environment

Fitment

Compatible with QMB139 50cc/49cc 4-stroke CVT scooters, including:

• Baja SC50
• Kymco (select 50cc models)
• Panterra
• Roketa
• Schwinn
• SUNL
• Tank
• Various unlisted Chinese 50cc QMB139-powered scooters

Technical Specifications

• Engine: QMB139 50cc / 49cc 4-stroke
• Overall Length: 97mm
• Width (outer diameter): 57mm
• Spring Type: Conical compression (torque / driven pulley spring)
• Material: Steel, dark oxide finish
• MPN / SKU: 151-144

California Prop 65 Warning: www.p65warnings.ca.gov

• Conical compression torque spring — controls CVT belt engagement rate in the driven pulley as engine load increases
• 97mm overall length — matches OEM torque spring for compatible QMB139 driven pulleys (verify before ordering)
• 57mm outer coil diameter — fits the driven pulley spring seat on compatible QMB139 CVT assemblies
• Dark oxide steel construction — corrosion resistant for CVT housing environment
• Restores factory CVT performance — fixes sluggish acceleration and belt slip caused by fatigued spring

Engine: QMB139 50cc/49cc 4-stroke | Length: 97mm | Width (OD): 57mm | Type: Conical compression (driven pulley/torque spring) | Material: Steel, dark oxide | MPN: 151-144 | SKU: 151-144

QMB139 50cc/49cc 4-stroke CVT scooters — Baja SC50, Kymco, Panterra, Roketa, Schwinn, SUNL, Tank, and various unlisted Chinese 50cc QMB139-powered scooters