Polaris Trail Boss 9921784 - Manual (Page 91)

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MAINTENANCE
PVT System
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 cen-
trifugal force decreases, reducing the amount of belt pinch. This begins
to occur at speeds of less than 5 MPH (8 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), the
engine would be running at only about 1500 RPM, with an engagement
speed of about 1400 RPM. Whenever operating this close to the engage-
ment 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.
If the ATV will be operated for extended periods below 5 MPH (8 km/
h), or for towing loads, we recommend that you install a one tooth
smaller counter shaft sprocket to raise the operating RPM far enough
above the engagement RPM to reduce heat caused by incomplete
engagement. Reducing the temperature inside the clutch cover greatly
extends the life of the PVT components (belt, cover, etc.).
Tip: Avoid heavy pulling and extended low-speed operation.