Compression springs do a couple of things. First they supply the pressure to engage the belt. They also determine the rate at which the CVT transmission changes from low to high gear. A 1000rpm spring will go into a higher gear than a 2000rpm spring.

This NCY 1500 rpm compression spring is specifically for the GY6.

Measurements:

Wire Diameter: 4.2mm

Inner DIameter: 48.5mm

Length: 154.0mm

Get better acceleration on your GY6 by upgrading your clutch springs! 1500 RPM NCY clutch springs, set of 3. Clutch springs help determine the RPM that the clutch will engage at.