7.3
CVT / TRANSMISSION
7
9923983 - 2012-2013 RZR 170 Service Manual
© Copyright 2012 Polaris Sales Inc.
CVT SYSTEM
The Continuously Variable Transmission (CVT) consists
of three major assemblies: 1) The Drive Clutch; 2) The
Driven Clutch; and 3) The Drive Belt. The internal
components of the drive clutch and driven clutch control
engagement (initial vehicle movement), clutch upshift and
backshift. During the development of a Polaris RZR, the
CVT system is matched first to the engine power curve;
then to average riding conditions and the vehicle’s
intended usage. Therefore, modifications or variations of
components at random are never recommended. Proper
clutch setup and careful inspection of existing
components must be the primary objective when
troubleshooting and tuning.
CVT Maintenance / Inspection
Under normal operation the CVT system will provide years
of trouble free operation. Periodic inspection and
maintenance is required to keep the system operating at
peak performance. The following list of items should be
inspected and maintained to ensure maximum
performance and service life of CVT components. See
“CVT Overheating / Water Ingestion Diagnostics” on
page 7.4 for more information.
1.
Drive clutch rollers and sheave bushing.
2.
Driven clutch rollers, pins, spring, centrifugal friction
shoes, and transmission drive hub.
3.
Clutch sheave faces. Clean and inspect for wear.
4.
CVT system sealing. The CVT system is air cooled by
fins on the drive clutch. The fins create a low pressure
area around the drive clutch, drawing fresh air in
through the intake duct. The opening for this intake
duct is located at a high point on the vehicle. All
connecting air ducts, as well as the clutch cover, must
be sealed to ensure clean air is being used for cooling
the CVT system. This also reduces the chance of
water and other contaminants entering the CVT area.
Drive Clutch Operation
Drive clutches primarily sense engine RPM. The major
component, which controls shifting function, are the shift
centrifugal weights (rollers) inside the moveable sheave.
Whenever engine RPM is increased, centrifugal force is
created, causing the rollers to push against the cam plate
and force the moveable sheave toward the drive belt. This
motion pinches the drive belt between the spinning
sheaves and causes rotation, which in turn rotates the
driven clutch. If belt speed is sufficient, centrifugal friction
shoes on the driven clutch overcome the return spring
pressure and swing outward against the transmission
drive hub, and the vehicle (if in gear) begins to move.
At lower RPM, the drive belt rotates low in the drive clutch
sheaves. As engine RPM increases, centrifugal force
causes the drive belt to be forced upward on drive clutch
sheaves, changing the ratio of the drive to driven clutch
from low to high.
Driven Clutch Operation
CVT driven clutches primarily sense torque, but also react
to RPM, applying and retracting the friction shoes
according to the forces applied to it from the drive belt. At
the same time it reacts to the torque at the transmission
input shaft. If the torque resistance at the transmission
input shaft is greater than the load from the drive belt, the
drive belt is kept at the outer diameter of the driven clutch
sheaves (low ratio).
As engine RPM and horsepower increase, the load from
the drive belt increases, resulting in the belt rotating up
toward the outer diameter of the drive clutch sheaves and
downward into the sheaves of the driven clutch. This
action, which increases the driven clutch speed, is called
upshifting.
Should the throttle setting remain the same and the
vehicle is subjected to a heavier load, the torque sensing
driven clutch will close, forcing the drive belt back up
toward the outer diameter of the driven clutch. This also
forces the belt downward into the sheaves of the drive
clutch. This action, which decreases the driven clutch
speed, is called backshifting.
In situations where loads vary and throttle settings are
constant, the drive and driven clutches are continually
shifting to maintain optimum engine RPM. At full throttle a
perfectly matched CVT system should hold engine RPM at
the peak of the power curve. This RPM should be
maintained during clutch upshift and backshift. In this
respect, the CVT system is similar to a power governor.
Rather than vary throttle position, as a conventional
governor does, the CVT system reacts to engine load
requirements by either upshifting or backshifting.
WARNING
All CVT maintenance or repairs should be performed
only by a certified Polaris Master Service Dealer (MSD)
technician who has received the proper training and
understands the procedures outlined in this manual.
Because of the critical nature and precision balance
incorporated into the CVT components, it is
absolutely essential that no disassembly or repair be
made without factory authorized special tools and
service procedures.