Polaris Magnum 330 - Manual (Page 111)

108
MAINTENANCE AND LUBRICATION
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
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, due to the system’s
dependence on engine speed.
For example, when operating at a ground speed of 3 MPH in low
range, the engine speed would be around 3000 RPM. This is well
above the engagement speed of 1200 - 1400 RPM. However, in high
range at 3 MPH, the engine would be running at only 1500 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 and causes outer clutch covers to fail.
By switching to low range while operating at low ground speeds, the
air temperature in the clutch cover is reduced by almost 160 degrees.
Reducing the temperature inside the clutch cover extends the life of the
PVT components (belt, cover, etc.).
When To Use Low Range vs. High Range
Following is a guideline for when to use low range and high range.
Low Range
S
When basic operation is at speeds less than 7 MPH
S
For heavy pulling
S
When operating in rough terrain (swamps, mountains, etc.) at low
ground speeds
High Range
S
When basic operation is at speeds greater than 7 MPH
S
When operating at high ground speeds