Caution, Inspect carburetor – John Deere stx38 User Manual

Page 62

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4/23/97

FUEL AND AIR SYSTEM REPAIR

ENGINE

INSPECT CARBURETOR

1. Disassemble bowl, float, inlet needle, low idle

mixture screw and spring.

IMPORTANT: Further disassembly of carburetor is

not required for general cleaning. Further
disassembly will require replacing parts with
new parts. DO NOT soak carburetor in
carburetor cleaner when fiber, rubber or foam
gaskets are still installed. Cleaner may damage
these components.

2. Clean carburetor using pressurized carburetor

cleaner and compressed air. Clean out all
passages.

3. DO NOT remove idle port welch plug unless

absolutely necessary. To remove, pierce with
sharp tool. Clean chamber. Install new plug using
a flat tool about the same size as plug. Flatten plug
but do not force below the surface of the cavity.

4. If inlet seat was leaking or damaged it can be

replaced by pulling it out with a drill bit or screw.
Always replace with new parts. Press in new seat
until it bottoms in bore.

5. If throttle and choke plates were removed, use a

high strength thread lock and sealer on the small
retaining screws. Install screws slightly loose.
Apply pressure on shafts to center plates in bore,
then tighten screws.

IMPORTANT: STX38 Serial Numbers

(STXH271285—272591 Gear)
(STXJ270811—272392 Hydro)—Float may stick
in carburetor bowl due to main jet not being
flush with carburetor body, this can cause fuel
in crankcase and exhaust. Inspect and repair
carburetor main jet as required. Removal of
carburetor is not necessary. You will be able to
feel the jet with your finger, or visibly see it, if it
is not completely pressed in. If main jet is not
completely flush, press jet flush to carburetor
body using a flat blade screwdriver and pliers.

6. Main jet can be pressed out. Replace with new jet

(high altitude jet is available). Press new jet in until
flush with surface.

7. Low idle mixture screw has a precision taper. If

screw is grooved, bent or broken this may indicate
seat damage and carburetor may need to be
replaced.

8. On standard carburetors, to set preliminary

adjustment for idle mixture screw—turn
clockwise until LIGHTLY seated and back
-out
(counterclockwise) one full turn
.

CARB/EPA Carburetor

9. On CARB/EPA carburetors, no preliminary

adjustment is required for idle mixture screw (A),
this is pre-set by manufacturer—only turn screw
(limited to maximum 1/4 turn in either
direction) until specified slow idle speed is
obtained (see Slow Idle Speed Adjustment,
earlier in Tests and Adjustments group of this
section)
.

Specifications:
Carburetor Float Bowl Cap Screw . 6 N•m (55 lb-in.)

c

CAUTION

Gasoline is explosive. Do not expose to flame or
spark. Serious injury can result. DO NOT expose
them to flame or spark. Follow the cleaner
manufacture’s warnings and instructions on its
proper and safe use. Never use gasoline as a
cleaning agent.

Choke Shaft

Throttle Shaft

Seal

Choke Spring

Body

Choke Plate

Throttle Plate

Idle Screw

Fuel Screw

Main Jet

Inlet Seal

Needle

Float

Float Bowl

Solenoid

M52127

Optional

Fuel Shut-Off

A

M58370

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