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