5-7. Carburetor, Cleaning, Inspection and Repair
a. Clean all metal parts of the carburetor in cleaning
solvent (Fed. Spec. P-D-680) and dry parts thoroughly.
b. If float valve is grooved or damaged, replace the
float valve and seat.
c. Check for looseness between throttle shaft and
lever assembly and throttle body. If looseness is noted,
replace the throttle shaft and lever assembly.
d. All packings and gaskets should be replaced at
e. Replace the idle adjusting needle if grooved or
Figure 5-3. Carburetor float setting.
overhauled, it is recommended that
kit parts be installed in place of old
parts even if damage is not noted.
Do not bend, twist or apply pressure
to float bodies. The float bodies
5-8. Carburetor, Reassembly and Installation
when viewed from the free end of the
bodies, must be centered and at right
(1) Install new packing (27) and retainer (26) on
angles to the machined gasket
the throttle shaft and lever assembly. Insert assembled
surface and must move freely on the
shaft in carburetor and tap lightly until retainer is flush
float axle shaft.
with casting face.
(2) Install throttle valve (12) on shaft with
(8) Install choke shaft retainer (53, fig. 5-2) and
identification mark on valve facing flange face of
packing (54) in the recess of the choke bracket (52) and
carburetor. Tap valve lightly to center in throttle bore
tap bracket in place on fuel bowl throat to seal packing.
and tighten screws (11) securely.
Secure bracket with screws (50) and lock washers (51).
(3) Install economizer jet (32), idle jet (31) and idle
Install bracket (47) and secure with screws (45) and lock
adjusting needle (14) with spring (15). Turn adjusting
needle (14) all the way in to seat then back off
(9) Install choke shaft (48) and return spring (49).
approximately one turn for preliminary setting.
Install choke valve (43) and spring (44) on lever and
(4) Position a new gasket (30) on float valve seat
center valve in casting before tightening screws (42).
and install float valve and seat (29) into throttle body
(10) Install main nozzle (41) through bottom of
casting. Place new packing (40) and a gasket (39) in
(5) Install new gasket (22) on throttle body. Install
recess and assemble power jet (38) and nozzle plug (37)
new packing (35) and venturi (36) on throttle body.
into fuel bowl.
(6) Position float (34) on throttle body and install
(11) Invert throttle body (21) and lower fuel bowl
axle shaft (33) through float lever.
(55) over floats. Be sure venturi (36) guides float bodies
(7) Measure distance from float to gasket on
throttle as shown on figure 5-3. Distance must be 0.250
(12) Install bowl screws (20) and tighten screws
inch (6.35mm) from gasket face to nearest edge of float.
gradually until all screws are secured. Install drain plug
If distance is not correct, use a long nosed pliers to bend
(1) in bottom of bowl.
lever to attain this measurement.
(13) Install levers (7 and 8) on shaft. Install spring
(6) and governor cams (5) over levers (7 and 8). Install
screws (3) and nuts (4 and 2) on governor cams. Install
stop screw (9) and spring (10) on shaft (13).
(14) Install block (18) and screw (19) on choke lever
and secure with washer (17) and clip spring (16).
(15) Install pin (28) and plugs (23, 24, 25 and 55).
b. Installation and Adjustment. Refer to TM 10-
3930-630-12 for installation and adjustments of