The Clutch Spring +1500 rpm is an aftermarket centrifugal clutch spring designed for use in the clutches of CVT transmissions on scooters equipped with GY6 125–150 cc engines, as well as some Kymco and Honda platforms using a similar mechanical clutch.
In a CVT transmission, the centrifugal clutch progressively engages the engine and the belt according to engine speed: at low RPM, it is disengaged, then it engages as the centrifugal force overcomes the spring's resistance. The clutch spring's role is therefore to define the RPM at which the clutch begins to engage significantly.
A spring rated at +1500 rpm is stiffer than most standard springs: it requires a higher centrifugal force (and therefore a higher engine speed) for the clutch masses to fully engage. This shifts the engagement point to slightly higher RPMs, which can be desirable for improving traction, smoother acceleration, and consistent engine-to-transmission response.
This type of spring is particularly relevant in setups where:
the usable power is generated more broadly in the upper mid-range,
the transmission has been tuned (heavier rollers, optimized variator, variator springs),
a more direct and controlled throttle response is desired.
