TM 9-2320-211-20
(2) Idle adjustment (with vacuum gage).
c. Installation.
CAUTION
(1) Position the air cleaner body (q) on the
Do not turn the idle adjusting screw in far
right frontside of the cab cowl, draw the ends of the
enough to jam the needle valve on the end
upper mounting band together, install a screw in
of the screw against the valve seat. If this
holes in the ends of the band, install the horn line
occurs, the needle valve wiil be damaged
retaining clip on the screw, and install the nut and
and will require replacement of the idle
tighten it.
adjusting screw before a satisfactory engine
(2) Position the three vent lines at the coupling
idle adjustment can be made.
and elbow assembly at the left side of the air cleaner
NOTE
body, and tighten the connectors.
Both idle adjusting screws must be turned
(3) Slide the upper end of the air cleaner outlet
out the same number of turns (to provide
hose (12) on the outlet tube at the left side of the air
equal clearance between the valve seats and
cleaner, and tighten the hose clamp.
adjusting screw needle valves) to provide a
( 4 ) Slide the air cleaner-to-air compressor
maximum performance in the engine speed
intake line (11) on the outlet tube at the front of the
range just above idling speed.
air cleaner, and tighten the hose clamp (vehicles
equipped with air cleaner-to-air compressor intake
the right side of the intake manifold, and insta!l the
line hose only).
vacuum gage in the pipe plug hole.
(5) Slide the air cleaner-to-carburetor inlet
hose (10) on the outlet sleeve at the left side of the
(b) Adjust the throttle as in (1) above.
(c) Turn the idle adjusting screws (fig. 2-
air cleaner, and tighten the hose clamp.
65), one at a time, until the vacuum gage indicates
(6) Install the oil cup (a (8) above).
the highest steady manifold vacuum. Turning the
2-64. Ventilation Lines and Fittings
i d l e adjusting screws in (clockwise) provides a
Refer to paragraph 2-48 for removal and in-
leaner idle mixture, and turning the idle adjusting
stallation of ventilation lines and fittings.
screw out (counterclockwise) provides a richer idle
Carburetor
mixture.
a. Adjustment.
(d) Check the idle adjusting screw settings.
NOTE
1. T u r n o n e i d l e a d j u s t i n g s c r e w i n
Make sure engine is sufficiently warmed up
(clockwise), counting the number of turns, until the
before adjusting the carburetor.
needle valve on the end of the screw just touches the
(1) T h r o t t l e a d j u s t m e n t . T h e t h r o t t l e a d -
valve seat; t h e n turn the adjusting screw out
j u s t i n g screw (fig. 2-65) controls the degree of
(counterclockwise) the same number of turns.
throttle valve plate opening when the throttle valve
2. Repeat the operation for other idle
lever is in the idling position and is adjusted as
adjusting screw.
i n d i c a t e d below.
(e) If the idle mixture adjustment results in
an increase in idling speed great enough to require
(a) Start the engine.
(b) Check the accelerator to make sure it is
resetting the throttle adjusting screw, the idle
completely released, and that the throttle and choke
adjusting screws must also be re-set.
control are pushed completely in against the in-
(f) W h e n e n g i n e i d l e a d j u s t m e n t i s
strument panel.
satisfactory, stop the engine.
(c) Turn the throttle adjusting screw clock-
(g) Remove the vacuum gage and install the
wise to increase, or counterclockwise to decrease
pipe plug in the threaded hole, and tighten it
the engine idle speed. The tachometer should read
securely.
400-450 rpm.
(3) I d l e a d j u s t m e n t ( w i t h o u t v a c u u m g a g e ) .
(a) Adjust the throttle adjusting screw.
in (clockwise) until the engine speed begins to
drop; then turn the adjusting screw out (coun-
terclockwise), counting the number of turns, until
the engine speed again begins to drop.
(c) Set the idle adjusting screw halfway
between the two points determined in (b) a b o v e .
( d ) R e p e a t t h e p r o c e d u r e s (b) a n d ( c )
above for the other idle adjusting screw, being sure
that it is set equally with the first screw.
