Polaris Sportsman 400 H.O. Owner's Manual page 119

Carburetor
Your Polaris ATV is calibrated at the factory for optimal performance at
altitudes ranging from zero to 6,000 feet (1800 m) and temperatures of
+40 degrees F. (4 degrees C.) or higher. Above 6000 feet (1800 m) the
engine air/fuel mixture becomes overly rich and the engine loses
approximately 3% of its power for each 1000-foot (304.8 m) increase in
elevation. Although this power cannot be regained, adjustments to the
carburetor and drive system can be made to allow more efficient opera-
tion. Optional jets, available from your Polaris dealer, are required for
operation above 6,000 feet and temperatures below +40 degrees F. (4
degrees C.)
NOTE:
Continuous operation of the engine without proper jetting when
required can cause poor performance, overheating or PVT or engine
damage. See your Polaris dealer for more information about jetting the
ATV for conditions in your area.
Carburetor/Engine Idle RPM Adjustment
If the engine idle speed is not satisfactory, and all other conditions are
favorable, the carburetor can be adjusted.
1. Place the transmission in
gear.
2. Lock the parking brake.
3. Start the engine and allow it to
warm up for approximately
five minutes.
4. Turn the screw in (clockwise)
to raise RPM. Turn the screw
out (counterclockwise) to
lower RPM.
ADJUSTMENTS
Idle
Adjuster
119