High Altitude Carburetor Adjustment - Honda TRX450ER Owner's Manual

High Altitude Carburetor Adjustment

Your engine's air-fuel mixture becomes overly rich when operated at
high altitudes. Above 1,500 m (4,500 feet), a rich mixture can cause
driveability problems, reduce engine performance, and increase fuel
consumption. To compensate, you can have the carburetor adjusted for
high altitude riding. See your Honda dealer.
A high altitude jet is available to compensate for high altitude richness.
For those who are mechanically proficient and have the necessary tools,
installation and adjustment procedures are given in the official Honda
Shop Manual available from your Honda dealer. All others should have
this carburetor modification performed by a Honda dealer.
However, the carburetor must be returned to standard factory
specifications before riding again at lower altitudes (below 1,500 m,
4,500 feet).
Sustained riding at lower altitudes with the lean high-altitude setting
may cause rough idling, stalling, or engine damage from overheating.
Altitude range Main jet
0 1,500 m No. 122
(0 5,000 feet)
1,000 2,500 m No. 118
or higher
(3,000 8,000 feet)
206 Technical Information
By-starter jet Pilot screw
No. 75 Factory preset
No. 72 Screw in 1/4
turn clockwise
from factory
preset
Throttle stop
screw
Factory preset
Screw in 1/4 turn
clockwise from
factory preset