Check variator rollers and sliders

Home mechanic (basic tools) · Time: 45 to 90 min (estimate)

Inside the front pulley (the variator) are small heavy rollers in sloping tracks. As the engine speeds up, the rollers move outwards and push the pulley halves together, which moves the belt up the pulley like changing to a higher gear. Small plastic sliders guide the back plate (ramp plate). When rollers wear flat, the pulley moves in jumps: the scooter accelerates unevenly, rattles, and does not reach its top speed. The K-Light manual's generic power-loss chart lists worn rollers and worn or grooved pulley faces as causes. Roller sizes and weights are model-specific; follow your scooter's manual.

Safety

• Engine and exhaust cool before you start.
• Use a holding tool that cannot slip on the variator.
• Keep grease and oil off the belt and pulley faces.

You need

• Tools to open the drive case and remove the variator (see Inspect and replace the scooter drive belt).
• A vernier caliper; brake cleaner and rags.
• New rollers as a complete set of the correct size and weight, and new sliders if worn.

Steps

1. Open the drive case and remove the variator nut and front pulley assembly, as on the belt page. Slide the belt aside.
2. Hold the variator face upwards and lift off the ramp plate. Keep the rollers in their tracks until you have looked at them.
3. Take out each roller. A good roller is round. Look for flat spots, steps, or a worn, angular shape.
4. Measure each roller's diameter across several points with the vernier and compare with your manual's minimum. Replace all rollers as a set if any are worn; mixed rollers make the pulley move unevenly.
5. Check the roller tracks in the variator for deep wear or pits.
6. Check the sliders on the ramp plate. Replace them if cracked, worn thin or loose.
7. Check the pulley boss and the bushing it slides on. The movable half should slide smoothly with no rocking.
8. Clean the pulley faces with brake cleaner. Look for grooves or blue heat marks; grooved faces need replacing.
9. Fit the rollers the way your manual shows (some are directional). Do not grease rollers unless your manual says so.
10. Refit the ramp plate, check the belt is not trapped, and tighten the variator nut to your manual's torque.
11. Refit the cover and test ride.

Check your work

• The scooter accelerates smoothly, with no surges, and no rattle from the case.
• Top speed is back to normal on a flat road.

Note on changing roller weight

Lighter or heavier rollers change when the scooter "changes up". This changes acceleration and top speed and can make a scooter illegal to ride on public roads. Fit the weight your manual specifies.

If it did not fix the problem

• Still slow at the top: Scooter will not reach its normal top speed.
• Still revs but slips: check the belt and the clutch (Check the scooter clutch and bell).