Variators are used in every just about scooter on the market, with the very rare exception being some manual transmission Vespa’s like the PX, Sprint, PK, and the early Lambretta’s.
A variator itself is the main part of a continually variable transmission (CVT). Where a gearbox has gears, each with a fixed gear radio, a CVT smoothly transitions through its gearing range.
Variators are used in scooters, and even some modern cars for a couple reasons. Firstly they’re fully mechanically automatic. No computers, electronic controllers or other complex parts that are prone to failure. They’re simple, easy to maintain and cheap to repair. The second reason is that theyre highly efficient particularly in low power engines.
Unlike conventional gearboxes, CVT transmissions change their gearing around the revs of the engine – rather than the engine changing revs around the gearing. In a conventional gearbox, the engine will rev through to or through its peak torque through each gear, with the engine always having to work up to its peak performance and efficiency. In a CVT transmission, the engine can rev to its peak performance and effieciency and stay there – while the CVT changes gearing, smoothly and continually according to the speed of the vehicle and the revs of the engine.
A variator is the front, or driven part of the CVT. This is the part that controls the progression of the variator (forcing the gearing ratio down, meaning higher speed)