TM 9-3431-254-14&P
INSPECTION OF PARTS
Adjust the idle adjusting needle to obtain smooth idling of
the engine at idling speed. Turn the needle out (counter-
1. Float Assembly Replace if loaded with gasoline, da-
clockwise) to make the mixture richer, and in (clockwise)
maged or if float axle bearing is worn excessively. In-
to make it leaner.
spect float lever for wear at point of contact with fuel
valve needle. Replace if wear is excessive.
2. Float Axle Replace if any wear has occurred on the
bearing surface.
3. Fuel Valve (Needle & Seat) Assembly - Replace as a
complete unit. Wear of any of these parts can seriously
THROTTLE
affect the operation of the float.
PLATE
4. Idle Adjusting Needle Inspect tapered end of the
`(Partially
needle to make sure it is smooth and free of grooves.
CLOSED
Replace if pitted or grooved.
POSITION)
5. Gaskets, Seal and Retainer Replace all gaskets,
throttle shaft seal and retainer each time the carburetor
is overhauled.
6. Check Specifications. Verify the correctness of the
following parts. Numbers will be found on the parts.
Main Jet, Idling Jet and Fuel Valve.
Fig. B-102. CHOKE SYSTEM
REASSEMBLY
ASSEMBLY OF THROTTLE BODY
1. Install the fuel valve seat (31) and fibre washer (30),
using Zenith Tool No. C161-85.
SERVICE AND REPAIR PROCEDURE
IDENTIFYCARBURETOR
2. Install the main discharge jet (32), using a small screw-
driver.
Check the numbers on the metal identification disc pinned
to the top of the throttle "body or indented in it. The plain
3. Install fuel valve needle in seat (31), followed by float
number is the
sssembly number, the number with the
(36) and float axle (35). NOTE: Insert tapered end of
float axle (35) into float bracket on side opposite slot
and push through the other side. Press float axle (35)
into slotted side until the axle is centered in bracket.
Exploded view (Page B-75)
4. FLOAT SETTING
The exploded view identifies the serviceable component
a. Fuel Level. Check position of float assembly (36),
parts of the carburetor and shows their relationship to the
for correct measurement to obtain proper fuel level by
complete assembly. Use the key numbers on the exploded
using a depth gage. NOTE: Do not bend, twist, or
view to identify and locate parts when performing both the
apply pressure on the float body.
disassembly and assembly operations.
b. With bowl cover assembly (26) in an inverted position,
viewed from free end of float (36), the float body must
be centered and at right angles to the machined sur-
face. The float setting is measured from the machined
DISASSEMBLY
surface (no gasket) of float bowl cover to top side of
SEPARATE CARBURETOR BODIES
float body at highest point- This measurement should
Remove the three bowl assembly screws (45, 46) and
be 31/32", plus or minus 1/32".
separate fuel bowl (39) from throttle body (26).
c, Bending Float Lever. To increase or decrease dis-
tance between float body (36) and machined surface
DISASSEMBLE FUEL BOWL
(26) use long nosed pliers and bend lever close to
1. Remove then main jet plug (43) and fibre washer (42),
float body. NOTE: Replace with new float if position
using a 9/16 open end wrench.
is off more than 1/16".
2. Remove the main jet (41) and fibre washer (40), using
5. Install throttle body to fuel bowl assembly gasket (37)
Zenith Tool No. C161-83 main jet wrench.
on machined surface of throttle body (26).
3. Remove the Idle Jet (38), using a small screwdriver.
4. Remove the bowl drain plug (44).
6. Install idle adjusting needle (17) and spring (18). Screw
needle IN (clockwise) until it seats lightly against the
DISASSEMBLE THROTTLE BODY
idle discharge hole, then back it out 1 turns as a pre-
liminary idle adjustment.
1. Remove the float axle (35) by pressing against the end
with the blade of a screwdriver.
REASSEMBLE FUEL BOWL
2. Remove the float {36).
3. Remove the fuel valve needle (31), using the fingers.
1. Install the main jet (41) and fibre washer (40), using
4. Remove the fuel bowl to throttle body gasket (37).
Zenith Tool No. C161-83 main jet wrench.
5. Remove the main discharge jet (32), using a small
2. Install the main jet hex plug (43) and fibre washer
screwdriver.
(42), using a 9/ 16" open end wrench.
6. Remove the fuel valve seat (31) and fibre washer (30),
3. Install the idle jet (38), using a small screwdriver.
using Zenith Tool No. C161-85.
4. Install the bowl drain plug (44).
7. Remove the idle adjusting needle (17) and spring (18). ,
REASSEMBLE CARBURETOR BODIES
CLEANING
Install the three bowl assembly screws (45, 46) through
Thoroughly clean all metal parts in
Metalclene or
the fuel bowl and into the throttle body and draw down
Speedclene and rinse in cleaning solvent. Blow out all pas-
firmly and evenly.
sages in throttle body and fuel bowl with reduced air pres-
sure. Be sure all carbon deposits have been removed from
SPECIAL TOOLS
throttle bore and idle discharge holes. Reverse the flow of
The special tools recommended are:
compressed air throaugh all passages to insure the removal
of ail dirt. NEVER USE A DRILL OR WIRE TO CLEAN
1. C161-83 Main Jet Wrench.
OUT JETS OR IDLE HOLES.
2 C161-85 Fuel Valve Seat Wrench.
B-74