Motor Scooter : CVT Basics - Describes the basic operation of the CVT (Constant Variable Transmission) that is the automatic transmission for most modern scooters. It is a simple device, but it can be difficult to understand how the different parts, roller weights, variator pulleys, and contra springs all work together to provide you with twist-n-go ease. Any scooter driver should understand at least a bit about what is going on down there.