Yamaha RX10H, Owner'S Manual

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8-10
ESU00157
High altitude adjustments
Operating at high altitude reduces the performance of a
gasoline engine to about 3% for every 305 m (1,000 ft) of
elevation. This is because there is less air as altitude
increases. Less air means less oxygen available for com-
bustion.
Your snowmobile can be adjusted to overcome most of
the problems found in high altitude riding. Carburetor
adjustments are the most important. Less air at high alti-
tude makes the air/fuel ratio too rich, which can cause
poor performance. Common problems are hard starting,
bogging, and plug fouling. Follow the Main Jet Setting
chart which is available at a Yamaha dealer carefully.
Proper carburetion adjustments will correct the air/fuel
ratio.
Remember:
less air at higher altitude means there is
less horsepower available, even with proper carburetion.
Expect acceleration and top speed to be reduced at
higher altitudes.
To overcome operating with less power at high altitudes,
your snowmobile may also require different settings for
the drive chain gears and V-belt clutch to avoid poor per-
formance and rapid wear. If you plan to operate your
snowmobile at an altitude different from the area where
you bought it, be sure to consult a Yamaha dealer. They
can tell you if there are any changes necessary for the
altitude where you plan to ride.
CAUTION:
@
The drive chain gears and V-belt clutch should be
adjusted when operating over a high altitude of
900 m (3,000 ft). Consult a Yamaha dealer.
@
ESU00348
Adjusting the valve clearance
The valve clearance changes with use, resulting 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 peri-
odic maintenance chart.
U8FA10.book Page 10 Monday, June 17, 2002 12:08 PM