Arctic Cat 660 cc, Service Manual

Page: 121 / 396

4-8
Adjusting
Carburetor
(120 cc)
The carburetor has been calibrated for average riding
conditions; however, altitude, temperature, and general
wear may necessitate certain carburetor adjustments.
Since carburetor adjustments critically affect engine
performance, three external adjustments can be made
on the carburetor. These are the idle speed screw, pilot
air screw, and throttle cable.
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IDLE SPEED SCREW
The idle speed screw controls the seating position of
the throttle valve which in turn determines the proper
idle speed. Rotate the screw clockwise to increase
engine idle speed and counterclockwise to decrease
engine idle speed.
PILOT AIR SCREW
The pilot air screw determines the fuel/air mixture for
idling. To adjust the pilot air screw, use the following
procedure:
1. Carefully rotate the pilot air screw clockwise until
a light “seating resistance” is felt.
2. Rotate the pilot air screw counterclockwise 1 turn.
3. Start the engine and “fine tune” the pilot air screw
until the engine idles smoothly.
THROTTLE CABLE
The correct throttle cable adjustment is when (with the
engine OFF) the carburetor throttle is completely open
(against its limit) while the throttle lever lightly con-
tacts the handlebar grip. The throttle arm on the carbu-
retor should also contact the speed control screw when
the throttle lever is released.
To adjust the throttle cable, use the following proce-
dure:
1. Loosen the throttle cable wire binding screw.
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2. Pull all slack from the throttle cable wire and exert
slight tension on the wire.
3. Tighten the throttle cable wire binding screw.
SPEED CONTROL SCREW
The maximum speed of the snowmobile can be
reduced by adjusting the speed control screw.
To reduce the maximum speed, rotate the speed con-
trol screw clockwise. DO NOT EVER INCREASE
THE MAXIMUM SPEED BEYOND THE ORIGI-
NAL 8 MPH MAXIMUM!
! CAUTION
DO NOT force the pilot air screw when seating;
damage to the pilot air screw will result.
! WARNING
Do not attempt to adjust the throttle cable with the
engine running. Personal injury could result.
! WARNING
DO NOT operate the snowmobile when any compo-
nent in the throttle system is damaged, frayed,
kinked, worn, or improperly adjusted. If the snow-
mobile is operated when the throttle system is not
functioning properly, personal injury could result.