Carburetors; High-Altitude Settings; Valve Clearance; Engine Oil And Oil Filter Cartridge - Yamaha GCH I 237 Owner's Manual

Periodic maintenance and adjustment
5. Place the air filter element frame in the
original position.
6. Install the air filter case cover and attach
the air filter case by hooking all the fas-
teners.
7. Close the shroud.
ESU11912

Carburetors

The carburetors are an important part of the
engine and its emission control system,
which require very sophisticated adjustment.
Therefore, carburetor adjustments should be
left to a Yamaha dealer, who has the neces-
sary professional knowledge and experience.
ESU11942

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-al-
titude 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
50
the area where you bought it, be sure to con-
sult a Yamaha dealer. The dealer can tell you
if there are any changes necessary for the al-
titude where you plan to ride. NOTICE: The
drive chain gears and V-belt clutch should
be adjusted when operating above a high
altitude of 900 m (3000 ft). Consult a
Yamaha dealer.
[ECS00432]
ESU11951

Valve clearance

The valve clearance changes with use, result-
ing in improper air-fuel mixture and/or engine
noise. To prevent this from occurring, the
valve clearance must be adjusted by a
Yamaha dealer at the intervals specified in
the periodic maintenance chart.
ESU11977

Engine oil and oil filter cartridge

The engine oil level should be checked before
each use. In addition, the oil must be
changed and the oil filter cartridge replaced
at the intervals specified in the periodic main-
tenance and lubrication chart.
EWS00371
WARNING
Engine oil is extremely hot immediately af-
ter the engine is turned off. Coming into
contact with or getting any engine oil on
your clothes could result in burns.
ECS00483
NOTICE
 Do not run the engine with too much or
not enough oil in the oil tank. Oil could
spray out or the engine could be dam-
aged.
 Be sure to change the engine oil after
the first 800 km (500 mi) of operation,
and every 4000 km (2500 mi) thereafter
or at the start of a new season, other-
wise the engine will wear quickly.