Polaris Sportsman 450 2021 Owner's Manual page 142

MAINTENANCE
The basic operation of the POLARIS PVT system is dependent on engine speed
and vehicle torque requirements. As engine speed increases, the force exerted
on the movable drive sheave by the flyweights also increases. This, in turn,
increases the amount of pinch applied to the drive belt. Similarly, if the engine
speed decreases, the amount of centrifugal force decreases, reducing the
amount of belt pinch.
On POLARIS ATVs, the approximate gear ratio difference between high and low
range is 1:2.25. This difference in gearing affects the operation of the PVT,
especially at speeds less than 7 MPH (11 km/h), due to the system's
dependence on engine speed.
For example, when operating at a ground speed of 3 MPH (5 km/h) in low range,
the engine speed would be around 2700–3000 RPM. This is well above the
engagement speed of 1500-1800 RPM. However, in high range at 3 MPH (5 km/
h), the engine would be running at only 1500–1800 RPM. Whenever operating
this close to the engagement speed, the engine may be running at a speed too
low to provide the pinch needed to prevent belt slip. Belt slip is responsible for
creating the excessive heat that destroys belts, wears clutch components and
causes outer clutch covers to fail.
The air temperature in the clutch cover is substantially reduced by using low
range while operating at low ground speeds. Reducing the temperature inside
the clutch cover greatly extends the life of the PVT components (belt, cover,
etc.).
WHEN TO USE LOW RANGE AND HIGH RANGE
CONDITION
Operating at speeds less than 7 MPH
(11 km/h)
Towing heavy loads
Operating in rough terrain (swamps,
mountains, etc.)
Operating at speeds greater than 7
MPH (11 km/h)
140
RANGE TO USE
Low
Low
Low
High