A new CVT belt has square, unseated side faces. Until they have worn to match the
sheave angle, the contact patch is smaller than it looks, and a wide-open pull on a fresh belt glazes
it before it ever seats.
The procedure
- Fit the belt the right way round. Most have a direction marking; match it to the old one’s
orientation. - Check deflection against the manual. A belt that is a quarter-inch off in length changes the
ratio range and the break-in will not save it. - Run gently and variably for the first stretch — Ultimax publish the distance for their
belts. Varied load matters more than low load: steady-state cruising polishes one band of the belt
rather than seating the whole face. - No wide-open throttle. No towing. No deep snow pulls.
- Let it cool fully, then check deflection again and re-check after the first real ride.
Storage matters too
Belts take a set. Store a spare flat or hanging over a wide surface, not folded and not hanging
off a nail, and keep it out of sunlight and away from ozone sources. A spare that has been folded in
a tunnel bag for two seasons is not the spare you think it is.
Cold starts
A frozen belt is a stiff belt. The first few minutes of a cold morning are the most expensive ones
for a belt — let the machine warm and move gently before asking anything of it.