Chapter 4. FUEL SYSTEM REPAIR INSTRUCTIONS

TM 10-3930-621-34

CHAPTER 4

FUEL SYSTEM REPAIR INSTRUCTIONS

Section I. CARBURATOR

(3) File off the riveted or peened end of the

4-1. Description

throttle plate screws (7).

a. The carburetor used in this fuel system is a single

venturi, updraft type with fixed jets covering all speeds

Note. When such screws are riveted or peened

except idle. The flow of fuel through the main jet system

the threaded end of the too screws must be filed flat

is controlled by the size of the jet. The idle adjusting

before removal to avoid breakage or stripping of threads

screw controls the fuel mixture for the idle system.

in the shaft. In some cases it may be necessary to use a

b. It has an air-bleed well method of compression, and

small (1/") round file and cut slightly below the surface

idle fuel adjusting screw, and an idle throttle stop screw.

of the shaft because of a slight counterbore around the

The air intake of the carburetor is provided with a choke

screw hole.

valve.

4-2. Removal

Caution: Avoid striking and cutting the side

Refer to TM10-3930-621-12for remove procedures.

of the throttle body (47) bore or the throttle plate (6)

4-3. Disassembly

when filing the screws.

Note.

Before disassembling, clean carburetor with

(4) Remove the screws and pull out the throttle

cleaning compound, solvent (Spec. P-S-661). Dry

plate (6).

thoroughly with compressed air.

(5) Loosen clamping screws (46) on levers (38

and 42).

a. Refer to figure 4-1 and disassemble carburetor as

(6) Remove cotter pin (36) from spring retainer

follows:

(37) and remove retainer from shaft (49).

b. Remove two mounting bolts (50) and lock washers

(7) Remove pins (3) from shaft (49).

(51) from body (48).

(8) Slowly slide shaft (49) from throttle body (48),

c. Remove four screws (25) which attach throttle body

using caution in removing levers (38 and 42), spring (39)

to fuel bowl (20).

and drivers (40) as they fall from the shaft.

d. Separate throttle body from fuel bowl and discard

k. Remove the throttle shaft retainers (45) and seals

bowl gasket (16).

(5) from the throttle body shaft holes as follows:

e. Remove float mounting axle (17) and remove float

(1) Screw a fine thread taper tap into the retainer

(13) as follows:

and seal until it is firmly seated.

(1) Press screwdriver against axle (17) at slotted

(2) Insert long punch or rod through opposite

side of float hinge bracket and force through hinge

shaft hole and drive the punch against the end of the tap

bracket.

until the retainer and seal are free. Repeat operation for

(2) Remove axle completely with fingers from

other retainer and seal.

opposite side and remove float.

l. Remove drain plug (26) from outside bottom of fuel

f. Remove main jet plug (23), washers (22 and 24)

bowl.

and jet (21).

m. Remove main discharge jet (11) and washer (12)

g. Remove venturi I-4F.

from center of large opening in machined surface of fuel

h. Remove idle jet (47).

bowl.

i. Remove idle adjusting screw (9) and spring (8).

n. Remove well vent jet (15) from center of large

j. Remove throttle plate (6) shaft (49) and stop lever

opening in machined surface of the fuel bowl with a small

assembly (2) as follows:

screwdriver.

(1) Unscrew throttle stop screw (4) until threaded

o. Remove valve and seat (19) and washer (18).

end is flush with lever.

p. Disassemble the choke as follows:

(2) Make match marks with center punch on

(1) Remove the return spring (33) from choke

throttle body and all levers, to act as a guide to

shaft (31) and bracket (28).

reassemble these parts in the same position as

(2) Make match marks with a center punch or file

removed.

on choke bracket, air intake bore and lever to act as a

guide to reassemble these parts in same position as

when removed.

4-1