12
Carburetor
The carburetor has been calibrated for aver-
age riding conditions; however, altitude,
temperature, and general wear may necessi-
tate certain carburetor adjustments. Since
carburetor adjustments critically affect
engine performance, Yamaha recommends
that any changes in internal carburetor cali-
bration be made by an authorized Yamaha
Snowmobile dealer; however, three external
adjustments can be made on the carburetor.
These are the throttle stop screw, idle fuel
adjuster screw, and throttle cable.
0744-921
Throttle Stop Screw
This screw controls the seating position
of the throttle valve which in turn deter-
mines the proper idle speed. Rotate the
screw clockwise to increase engine idle
speed and counterclockwise to decrease
engine idle speed.
Idle Fuel Adjuster Screw
This adjuster screw determines the fuel/
air mixture for idling. To adjust, use the
following procedure:
1. Start the engine and allow to run at
half throttle 5-10 minutes to warm up.
2. Place the throttle in the idle position;
then rotate the idle fuel adjuster
screw/cap in or out within the
adjustment range to obtain smooth
low speed performance.
Throttle Cable
The correct throttle cable adjustment is
when (with the engine OFF) the carbure-
tor throttle is completely open (against its
limit) while the throttle lever lightly con-
tacts the handlebar grip. The throttle arm
on the carburetor should also contact the
speed control screw when the throttle
lever is released.
To adjust the throttle cable, use the fol-
lowing procedure:
1. Loosen the throttle cable jam nuts.
0744-922
2. Pull all slack from the throttle cable
wire and exert slight tension on the
wire.
3. Tighten the throttle cable jam nuts.
Speed Control Screw
0744-949
The maximum speed of the snowmobile
can be reduced by adjusting the speed
control screw.
To reduce the maximum speed, rotate the
speed control screw clockwise. DO NOT
EVER INCREASE THE MAXIMUM
SPEED BEYOND THE ORIGINAL 8
MPH MAXIMUM!
! WARNING
Do not attempt to adjust the throttle
cable with the engine running. Per-
sonal injury could result.
! WARNING
DO NOT operate the snowmobile
when any component in the throttle
system is damaged, frayed, kinked,
worn, or improperly adjusted. If the
snowmobile is operated when the
throttle system is not functioning
properly, personal injury could result.
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