Minarelli scooter Evolution clutch spring +15% Polini

Spring 55% at origin

The hardness of the contrast spring plays an important role in transmitting the engine's power to the rear wheel.
It exerts back pressure on the rear pulleys and therefore has a considerable influence on the operation of the variator. The contrast spring is usually harder if the belt tends to slip, if the variator does not operate at the optimal RPM level, or if the engine, despite light weights, continues to run below the optimal RPM.
What negatively affects engine performance is a twisted contrast spring.