Carburetor Repair

TM 10-3930-633-12

contents of the bowl may then be examined for

(9) Remove power valve piston assembly from

contamination as the carburetor is disassembled.

main body. Remove fast idle cam screw and fast idle

b. Removal. Refer to figure 4-29 and proceed as

cam.

follows:

(10) Remove spark valve and gasket, fuel inlet

(1) Remove the air intake elbow from the

and needle seat, and spark fitting, Remove pump

carburetor.

discharge valve weight and discharge valve ball,

(2) Disconnect the throttle return spring,

Remove power valve assembly. Remove main jet only

throttle cable, choke control cable and housing, fuel

if orifice appears burred, worn, or otherwise

inlet line, and the distributor vacuum line from the

damaged. This completes recommended disassembly.

carburetor.

c. Cleaning and Inspection. Dirt, gum, water or

( 3 ) Remove the two hex nuts from the

carbon contamination on the exterior moving parts of

mounting studs, and remove the carburetor assembly,

a carburetor are often responsible for unsatisfactory

c. Replacement.

performance. For this reason, efficient carburetion

(1) Clean the gasket mounting surface of the

depends upon careful cleaning and inspection while

carburetor intake manifold and velocity-type

servicing.

governor.

(1) Thoroughly clean carburetor castings and

(2) Install the governor mounting gasket,

metal parts in carburetor cleaning solvent.

governor, spacer lower gasket, spacer upper gasket

CAUTION

and the carburetor on the intake manifold.

Accelerator pump plunger and any fiber

(3) Connect the governor t u b e to the

o r rubber parts s h o u l d never be

carburetor. Install distributor vacuum line to the

immersed in carburetor cleaner. Wash

governor.

pump plunger in cleaning solvent.

(4) Install and tighten hex nuts over carburetor

mounting studs. Tighten nuts evenly and alternately.

(2) Blow out all passages in the castings with

(5) Connect the throttle control cable, throttle

compressed air. Make sure all jets and passages are

return spring and the choke control cable to the

clean, Do not use wire to clean fuel passages or air

carburetor.

bleeds.

(6) Adjust the idle fuel mixture and engine idle

(3) Check inlet valve needle and seat for wear.

speed to specification as outlined in paragraph 4-57.

If wear is noted, the assembly must be replaced.

(7) Install the air cleaner inlet elbow on the

(4) Check float hinge pin for wear and check

carburetor air inlet body.

float for damage,

(5) Check throttle and choke shaft bores for

4-58.1. Carburetor Repair

wear and out-of-round.

a. Removal. Refer to paragraph 4-58 and remove

(6) Inspect idle mixture adjustment needles for

the carburetor assembly from the engine.

burrs or grooves; replace if damaged.

b. Disassembly. Refer to figure 4-29.1 for parts

(7) Inspect cup of accelerator pump plunger;

identification and proceed as follows:

replace if damaged, worn, or hardened. Inspect

(1) Disconnect and remove the fast idle rod,

pump well in bowl for wear or scoring.

and the pump operating link. Unscrew and remove

(8) Check filter screens for dirt or lint. Clean,

the dashpot assembly from its bracket,

and if they remain clogged, replace.

(2) Remove the bowl cover screws, bowl cover,

(9) Check the three main castings carefully for

choke bracket, and dashpot bracket.

damage such as nicks, burrs, or cracks, around

(3) Remove the pump rod clamp screw, pump

gasket surfaces. Also check the condition and

rod and clamp from the bowl cover.

cleanliness of all threaded holes.

(4) Remove choke plate screws and plate, Pull

d. Reassembly.

choke shaft and lever out of bowl cover, and remove

choke lever spring and control lever.

NOTE

(5) Remove throttle body screws and separate

Always use new gaskets and seals when reassembling

main body from throttle body.

carburetor.

(6) Remove throttle plate screws and plate from

(1) Refer to figure 4-29.1 and reassemble the

throttle body bore. Remove nut, lockwasher, pump

carburetor assembly as follows:

operating lever, bushing and spring from throttle

(2) Install the fuel inlet needle and seat, with

shaft.

gasket, into the main body. Install the spark valve

(7) Pull throttle shaft out of throttle body.

and gasket, and the spark fitting,

Remove throttle adjusting screw and spring. Remove

(3) Install the fast idle cam, spring washer, and

i d l e adjusting needle and spring. - -

fast idle cam screw.

(8) Remove float shaft retainer, hinge shaft,

(4) Install power valve assembly, float and

and float assembly from main body. Remove pump

hinge assembly, float hinge shaft, and retainer.

drive spring, piston stem, and piston cup.

4-45

Change 1