High Altitude Adjustment - Honda 2005 FOURTRAX FOREMAN TRX500 TM Service Manual

FUEL SYSTEM
HIGH ALTITUDE ADJUSTMENT
At high altitude, the standard carburetor air-fuel
mixture will be too rich. Performance will decrease,
and fuel consumption will increase. A very rich mix-
ture will also foul the spark plug and cause hard
starting. Operation at an altitude that differs from
that at which this engine was certified, for extended
periods of time, may increase emissions.
High altitude performance can be improved by spe-
cific modifications to the carburetor. If your cus-
tomer always operates the ATV at altitudes above
6,500 feet (2,000 meters), you should perform this
carburetor modification.
Even with carburetor modification, engine horse-
power will decrease about 3.5% for each 1,000-foot
(300-meter) increase in altitude. The effect of alti-
tude on horsepower will be greater than this if no
carburetor modification is made.
This engine, when operated at high altitude with the
carburetor modifications for high altitude use, will
meet each emission standard throughout its useful
life.
The high altitude carburetor adjustment is per-
formed as follows:
P I L 0 T S C R E W
Remove the carburetor (page 6-6) and the float
chamber.
Replace the standard main jet with the high altitude
type.
HIGH ALTITUDE MAIN JET: #158
Check that the O-ring on the float chamber is in
good condition, replace it if necessary.
Install the float chamber and carburetor.
MAIN JET O-RING
Screw in the pilot screw the specified number of
turns from the factory preset position using the spe-
cial tool.
HIGH ALTITUDE PILOT SCREW OPENING:
3/8 turn in from the factory preset position
TOOL:
Pilot screw wrench, D type 07KMA-MN90101 or
07KMA-MN9A100
(U.S.A. only)
PILOT SCREW WRENCH
6-20