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7 - 2
T U N
●
After installing the carburetor, check that
the throttle operates correctly and opens
and closes smoothly.
Atmospheric conditions and carburetor
settings
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.
Air temp.
Humidity
Air
pressure
(altitude)
Mixture
Setting
High
High
Low (high)
Richer
Leaner
Low
Low
High (low)
Leaner
Richer
SETTING
Effects of the setting parts on the throttle
valve opening
Å
Closed
ı
Fully open
4/4
3/4
1/2
1/4
1/8
0
ı
Å
1/2
3/4
1/4
1/8
A
B
1
2
3
4
1
Pilot screw/Pilot jet
2
Piston valve cutaway
3
Jet needle
4
Main jet