Scooter variator (CVT) simulator

A scooter variator changes the gear ratio smoothly: rollers, the torque spring and clutch springs decide at what rpm the engine works. Choose a setup, press "Start" and watch the belt move, the clutch engage and the rpm and acceleration change.

Scooter type

Rider weight

Variator rollers (6 pcs)

Torque spring (rear)

Clutch springs – engagement (rpm)

Maximum engine speed (rpm)

With this setup the variator holds about rpm, the clutch starts to engage at about rpm. Peak engine power about kW ( rpm).

Engine rpm by speed

Red line – this run, grey dashed line – previous run.

Results

	This run	Previous run
0–30 km/h	–	–
0–50 km/h	–	–
100 m	–	–
Top speed	–	–
Shift rpm	–	–
Clutch engagement (rpm)	–	–

Results are calculated estimates. Always check your vehicle manufacturer's instructions.

How does a variator work?

2-stroke and 4-stroke engines

A 2-stroke engine makes little power at low rpm but revs high – the variator has to keep the rpm high and the roller choice has a big effect on acceleration. A 4-stroke engine has more torque at low rpm but runs out of revs earlier – it shifts at lower rpm and the rollers have a smaller effect.

Variator and rollers

The variator sits on the crankshaft with rollers inside. As rpm rises, centrifugal force throws the rollers outwards and they push the variator halves together. The belt climbs to a larger radius on the front pulley – the ratio gets taller, like shifting up a gear.

Drive belt

The belt connects the variator to the rear pulley. When the belt climbs at the front, it is pulled deeper at the rear and the rear pulley opens. The belt length never changes, so both radii change together.

Torque spring (rear spring)

The rear pulley spring pushes the pulley closed and pulls the belt up at the rear, towards the short ratio. The roller force and the spring force balance each other – this decides the rpm the engine holds while shifting. The torque cam on the rear pulley adds force under load, so the ratio stays shorter on hills.

Centrifugal clutch and clutch springs

The clutch sits on the rear pulley. As rpm rises, the clutch shoes are pressed against the clutch bell by centrifugal force and the scooter starts to move. The clutch springs hold the shoes back – the stiffer the springs, the higher the rpm at which the clutch engages.

Rules of thumb for tuning

Change	Effect
Lighter rollers	Higher rpm, better acceleration. Too light: the engine revs past peak power and top speed drops.
Heavier rollers	Lower rpm, calmer and more economical riding. Too heavy: weak acceleration.
Stiffer torque spring	Rpm stays higher and the ratio rises more slowly – better on hills and two-up.
Softer torque spring	Faster shift to the tall ratio, lower rpm and lower fuel consumption.
Stiffer clutch springs	The clutch engages at higher rpm – quicker launch, but more clutch and belt wear.
Softer clutch springs	Soft and smooth launch at low rpm.
Higher maximum rpm (tuned engine)	The power peak moves higher. The rollers must be lighter, otherwise the variator holds the engine below its power peak and acceleration is weaker than before.

The simulator uses typical data for the selected scooter type (engine torque curve, weight, gearing) and a simplified physics model. The results show the direction of changes, not exact figures for a specific scooter.

Matching products: Variator Rollers Pressure Springs Clutch springs Variator Belts

How to use

Choose the roller weight, torque spring strength and clutch springs.
Press "Start" – the simulator rides at full throttle for 22 seconds and shows the variator at work.
Change one setting and press "Start" again. The previous run stays on the chart and in the table for comparison.

Frequently asked questions

Which rollers suit my scooter?

Start from the factory weight and change in 0.5–1 g steps. Lighter rollers raise rpm and acceleration, but too light lowers top speed. The simulator shows the direction; check the result on the real scooter by riding.

Does a stiffer torque spring add power?

No, power stays the same. A stiffer spring keeps the engine at higher rpm where it makes more power and slows the shift to the tall ratio. It helps on hills and two-up, but increases fuel consumption.

Are the simulator figures exact?

The simulator uses typical data for the selected scooter type and a simplified physics model. It shows the direction and size of changes, not exact results for a specific scooter.

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