Yamaha WR400F(M) Owner's Service Manual page 608

ı
4/4
3/4
1/2
1/4
1/8
0
Å
Å Closed
ı Fully open
SETTING
After installing the carburetor, check that
the throttle operates correctly and opens
and closes smoothly.
Atmospheric conditions and carburetor
settings
Air temp. Humidity
High High
Low Low
The air density (i.e., concentration of oxygen
in the air) determines the richness or lean-
ness of the air/fuel mixture. Therefore, refer
to the above table for mixture settings.
That is:
Higher temperature expands the air with its
resultant reduced density.
Higher humidity reduces the amount of oxy-
gen in the air by so much of the water vapor
in the same air.
Lower atmospheric pressure (at a high alti-
tude) reduces the density of the air.
Effects of the setting parts on the throttle
valve opening
1
2
1/8 1/4
A
1 Pilot screw/Pilot jet
2 Piston valve cutaway
3 Jet needle
4 Main jet
7 - 2
T U N
Air
pressure Mixture Setting
(altitude)
Low (high) Richer Leaner
High (low) Leaner Richer
3
4
1/2 3/4
B