Carburetors; High-Altitude Settings - Yamaha RS Venture RST90Y Owner's Manual

2. Remove the air filter case cover.
3. Lift up the air filter element frame and
check the air filter element. If there is any
snow on the air filter element, remove the
element, brush off the snow, and then in-
stall the air filter element.
4. Place the air filter element frame in the
original position, and then install the air
filter case cover.
5. Install the air filter case cover by hooking
the fasteners.
Periodic maintenance and adjustment
TIP
After riding the snowmobile, make sure that
there is no snow under the air filter element
frame.
ESU11910

Carburetors

The carburetors are an important part of the
engine and its emission control system, which
require very sophisticated adjustment. There-
fore, carburetor adjustments should be left to
a Yamaha dealer, who has the necessary pro-
fessional knowledge and experience.
ESU11941

High-altitude settings

Operating at high altitude reduces the perfor-
mance of a gasoline engine about 3% for ev-
ery 305 m (1000 ft) of elevation. This is
because there is less air as altitude increases.
Less air means less oxygen available for
combustion.
Your snowmobile can be adjusted to over-
come most of the problems found in high-alti-
tude riding. Carburetor adjustments are the
most important. Less air at high altitude
makes the air/fuel ratio too rich, which can
cause poor performance. Common problems
are hard starting, bogging, and plug fouling.
Proper carburetion adjustments will correct
the air/fuel ratio. Be sure to have a Yamaha
dealer make these adjustments.
Remember:
Less air at higher altitude means there is less
horsepower available, even with proper car-
buretion. Expect acceleration and top speed
to be reduced at higher altitudes.
To overcome operating with less power at
high altitudes, your snowmobile may also re-
quire different settings for the drive chain
gears and V-belt clutch to avoid poor perfor-
mance and rapid wear. If you plan to operate
your snowmobile at an altitude different from
the area where you bought it, be sure to con-
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