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CARBURETION
Carburetor Identification
IntekTM
Single Cylinder OHV Engine Repair Manual
Version 1.0Copyright© 1999 by Briggs and Stratton Corporation
Models 28S700, 311700Models 110400, 110600, 111400, 111600, 113400, 120400,
120600, 121400, 121600, 122600, 123400, 123600
Models 28S700, 3117002
These carburetors have a fixed high speed main jet with
adjustable idle mixture, Fig. 22. The different carburetors
are identified as LMT 1 and up.
The letters LMT are cast into the body of the carburetor
while the numbers are stamped into carburetor mounting
flange next to idle mixture screw.
CARBURETION
Large B&S/Walbro
Service Carburetor Briggs & Stratton/Walbro LMS
IntekTM
Single Cylinder OHV Engine Repair Manual
Version 1.0Copyright© 1999 by Briggs and Stratton Corporation
Fig. 22 - Outside View, Carburetor Typical
Remove Carburetor
Models 28S700, 311700
1. Disconnect wire(s) from carburetor solenoid.
2. Remove two (2) carburetor studs while holding
carburetor.
3. Pull carburetor away from governor control bracket
and rotate carburetor to disengage Choke-A-Matic®
linkage, governor link, and governor link spring from
carburetor, Fig. 25.
CARBURETION
Large B&S/Walbro
Remove
IntekTM
Single Cylinder OHV Engine Repair Manual
Version 1.0Copyright© 1999 by Briggs and Stratton Corporation
Fig. 25 - Remove Carburetor
Disassemble Carburetor
Models 28S700, 311700
1. Remove anti-afterfire solenoid and fuel bowl washer.
2. Remove float bowl and float bowl gasket.
3. Remove float hinge pin, float, and inlet needle.
4. Remove idle mixture needle limiter cap, when used.
5. Remove idle mixture screw with spring and idle
speed screw with spring.
6. Rotate throttle shaft and lever to closed position and
remove two (2) throttle plate screws.
7. Remove throttle plate, throttle shaft, and foam seal.
8. Remove throttle shaft seal or bushing.
Note: These carburetors are equipped with one of
two styles of choke shafts:
a. Plastic shaft with snap in choke plate or;
b. Metal shaft with screw mounted choke plate.
Remove Choke Shaft & Plate (Metal)
1. Rotate choke shaft and lever to closed position.
Note: Service replacement carburetors may have a
spring detent.
2. Hold choke closed and remove two (2) screws
holding choke plate.
3. Remove plate. Release tension on choke shaft and
remove choke shaft and lever, return spring and seal
assembly.
Remove Choke Shaft & Plate (Plastic)
1. Rotate choke shaft to wide open position.
2. Pull choke plate out of choke shaft and lever.
3. Remove choke shaft and lever, return spring (when
used), and foam washer.
CARBURETION
Large B&S/Walbro
Disassemble
IntekTM
Single Cylinder OHV Engine Repair Manual
Version 1.0Copyright© 1999 by Briggs and Stratton Corporation
Page 1 of 4
Fig. 33 - Remove Metal Choke Shaft
Fig. 34 - Remove Plastic Choke Shaft
Fig. 32 - LMT Exploded View
4. Using Tool #19062, Carburetor Screwdriver, remove
main carburetor emulsion tube, Fig. 27
.Note: Low Emission LMT carburetors have pressed
in pilot jets that are not removable.
DO NOT remove the pressed in style pilot jet,
Fig. 28.
CARBURETION
Large B&S/Walbro
Disassemble
IntekTM
Single Cylinder OHV Engine Repair Manual
Version 1.0Copyright© 1999 by Briggs and Stratton Corporation
Page 2 of 4
Fig. 27 - Remove Emulsion Tube
Fig. 26 - Pressed-In Pilot Jet Welch Plug
5. With a modified 5/16 inch (4 mm) pin punch, remove
welch plug from carburetor body, Fig. 43.
Remove Fuel Inlet Seat
1. Use self-threading screw Part #93029 from Tool
#19165, Flywheel Puller, or 1/4-20 tap.
2. Thread screw or tap into fuel inlet seat 3-4 turns and
remove, Fig. 44.
CARBURETION
Large B&S/Walbro
Disassemble
IntekTM
Single Cylinder OHV Engine Repair Manual
Version 1.0Copyright© 1999 by Briggs and Stratton Corporation
Page 3 of 4
Fig. 28 - Remove Welch Plug
Fig. 29 - Threading Or Tapping Into Fuel Inlet Seat
3. Place 1/4" x 20 nut Part #92278 and washer,
Part #224061 from 19332, Tool Kit, onto puller screw.
4. Place a 1/4" drive 3/8" socket over fuel inlet seat.
5. Thread screw into tapped inlet seat until screw
bottoms.
6. Thread nut down unto washer and continue turning
nut until inlet seat is free from carburetor body,
Fig. 45.
CARBURETION
Large B&S/Walbro
Disassemble
IntekTM
Single Cylinder OHV Engine Repair Manual
Version 1.0Copyright© 1999 by Briggs and Stratton Corporation
Page 4 of 4
Fig. 30 - Remove Fuel Inlet Seat
CARBURETION
Large B&S/Walbro
Carburetor Cleaning Recommendations
IntekTM
Single Cylinder OHV Engine Repair Manual
Version 1.0Copyright© 1999 by Briggs and Stratton Corporation
Carburetor Cleaning Recommendations
1. Disassemble carburetor.
2. Remove all old gaskets, seals and sealing material.
3. Use commercial carburetor cleaning solvents (such as Briggs & Stratton Spray Cleaner, Part #100041 or #100042) to clean
carburetor parts and body.
4. When cleaning non-metallic parts (plastic, nylon, Minlon, etc.), do not leave in commercial carburetor cleaner bath more than
15 minutes.
Note: Parts containing rubber, such as seals, "O" rings or pump diaphragms should never be placed in commercial
carburetor cleaner bath.
5. Use only compressed air (blowing in both directions) to clean out all openings and passages.
Note: Do not use wires, drills or any other devices to clean out metering holes or passages.
Install Welch Plug
1. Install welch plug with pin punch slightly smaller than
outside diameter of plug. Press in until plug is flat.
DO NOT cave in plug.
2. After plug is installed, seal outside edge of plug with
fingernail polish or non-hardening sealant, Fig. 31.
Install Fuel Inlet Seat
Using Tool #19135, Knockout Pin, press new fuel inlet
seat in until flush with fuel inlet boss, Fig. 32.
CARBURETION
Large B&S/Walbro
Assemble Carburetor
IntekTM
Single Cylinder OHV Engine Repair Manual
Version 1.0Copyright© 1999 by Briggs and Stratton Corporation
Page 1 of 3
Fig. 31 - Install Welch Plug
Fig. 32 - Install Fuel Inlet Seat
Install Metal Choke Shaft
1. Install foam seal and return spring on choke shaft
hooking small hook in notch on choke lever, Fig. 33,
inset.
2. Insert choke shaft assembly into carburetor body and
engage large end of return spring on boss.
3. If carburetor has spring detent, guide detent spring
into slot on choke shaft lever, Fig. 33.
4. Place choke plate on shaft with single notch on edge
towards fuel inlet. Two (2) half moon dimples will help
to position plate on shaft.
Install Plastic Choke Shaft
1. Insert spring inside large foam seal and slide seal and
spring onto choke shaft with straight end of spring up
toward choke shaft lever.
2. Insert choke shaft into carburetor body until hook of
spring hooks on spring anchor.
3. Lift choke shaft and lever up slightly and turn
counterclockwise until stop on lever clears spring
anchor and push shaft down, Fig. 34.
4. Insert choke plate into choke shaft and lever with
dimples toward fuel inlet side of carburetor. Dimples
help to hold and align choke plate on shaft, Fig. 34.
Install Throttle Shaft
Models 28S700, 311700
1. Install throttle shaft seal with sealing lip down in
carburetor body until top of seal is flush with top of
carburetor.
2. Install throttle shaft and small foam washer.
Turn shaft until flat is facing out.
3. Lay throttle plate on shaft with numbers toward idle
mixture screw and dimples facing in resting on edge
of shaft. Install two (2) screws, Fig. 35.
CARBURETION
Large B&S/Walbro
Assemble Carburetor
IntekTM
Single Cylinder OHV Engine Repair Manual
Version 1.0Copyright© 1999 by Briggs and Stratton Corporation
Page 2 of 3
Fig. 33 - Install Metal Choke Shaft
Fig. 34 - Install Plastic Choke Shaft
Fig. 35 - Install Throttle Shaft
Install Inlet Needle & Float
1. Insert inlet needle in slot on float.
2. Place float and needle on carburetor and install float
hinge pin centering hinge pin.
3. Place bowl gasket on carburetor body.
4. Place bowl on carburetor and install solenoid and
float bowl washer torquing solenoid to 40 in. Lbs.
(5 Nm).
Install Idle Mixture Screw
Install idle mixture screw with spring and turn until head
of screw touches spring.
Install Emulsion Tube
1. Install emulsion tube using Tool #19062, Carburetor
Screwdriver, until tube seats, Fig. 51.
2. After installing emulsion tube, use compressed air to
blow out any chips or debris that may have been
loosened while installing tube.
Note: On Models 28S700, 311700, install main jet
after installing emulsion tube.
CARBURETION
Large B&S/Walbro
Assemble Carburetor
IntekTM
Single Cylinder OHV Engine Repair Manual
Version 1.0Copyright© 1999 by Briggs and Stratton Corporation
Page 3 of 3
Fig. 36 - Install Emulsion Tube
Fig. 35 - Install Inlet Needle & Float
Install Intake Manifold
If carburetor elbow was removed, place new gasket
and manifold on intake port and torque screws to 100 in.
Lbs. (11 Nm).
Install Governor Link and Spring
1. Place two (2) studs on carburetor and new gasket on
studs with long edge on side of gasket opposite fuel
inlet.
2. Hook governor link spring in throttle lever hole without
grommet.
3. Hook governor link in throttle lever hole grommet with
link on top of lever.
Install Choke-A-Matic® Link and Carburetor
1. Insert "U" bend of Choke-A-Matic® link in outer hole of
choke lever from bottom of lever.
2. Slide "U" bend of link into slot on governor control
bracket and place carburetor on intake elbow.
Torque studs to 65 in. Lbs. (7 Nm), Fig. 37.
3. Install air cleaner body and torque nuts to 55 in. Lbs.
(6 Nm). Then install screw inside air cleaner body.
4. Install breather tube in air cleaner body opening.
5. Install air cleaner brace.
CARBURETION
Large B&S/Walbro
Install Carburetor - Models 28S700, 311700
IntekTM
Single Cylinder OHV Engine Repair Manual
Version 1.0Copyright© 1999 by Briggs and Stratton Corporation
Fig. 37 - Install Carburetor
Fig. 36 - Install Carburetor
Adjust Carburetor
1. Start and run engine for 5 minutes at 1/2 throttle to
bring engine up to operating temperature.
2. Move equipment control to idle position.
3. Turn idle speed screw to obtain 1750 RPM Minimum.
4. Turn idle mixture screw slowly clockwise until engine
just begins to slow.
5. Then turn screw opposite direction until engine just
begins to slow. Turn screw back to midpoint.
6. Install limiter cap with flat facing up, (when so
equipped) Fig. 38.
Note: If engine is adjusted for governed idle, reset idle
speed screw to 1200 RPM. For governed idle
adjustment procedure see Section 5.
7. Move equipment speed control from idle to high speed
position. Engine should accelerate smoothly. If it does
not, open idle mixture needle screw 1/8 turn open.
There should be no afterfire.
CARBURETION
Large B&S/Walbro
Adjust Carburetor
IntekTM
Single Cylinder OHV Engine Repair Manual
Version 1.0Copyright© 1999 by Briggs and Stratton Corporation
Fig. 38 - Install Limiter Cap
Test Solenoid, Current Style
Models 28S700, 311700
1. Insert jumpers in connector on side of solenoid.
2. Test solenoid by connecting jumper wires to a new
9 volt transistor battery.
3. Plunger needle should snap into solenoid body.
If not, replace.
Test Solenoid, Early Style
Models 28S700, 311700
1. Test solenoid by connecting jumper wire from positive
post of a new 9 volt transistor battery to solenoid
terminal.
2. Touch body of solenoid to negative post of battery.
Plunger needle should snap into solenoid body. If not,
replace.
CARBURETION
Large B&S/Walbro
Anti-Afterfire Solenoid
IntekTM
Single Cylinder OHV Engine Repair Manual
Version 1.0Copyright© 1999 by Briggs and Stratton Corporation
Fig. 24 - Solenoid Types
Anti-Afterfire Solenoid
Afterfire can be caused by broken wires, poor grounds, defective solenoid or wiring of the ignition switch.
Afterfire can be caused by using the anti-afterfire terminal of the five (5) terminal key switch to also turn off the alternator
when the engine is shut off. When the key is turned to the off position, as long as the engine continues to slow down, the
alternator is putting out voltage and current. This current will flow through the anti-after fire solenoid allowing fuel to go
through the engine into the hot muffler causing after fire. If the equipment is wired this way, replace the five (5) terminal
switch with a six (6) terminal switch using the correct diagram for the type of alternator used, as shown in MS-0415.
Note: Two (2) styles of solenoids have been used, Fig. 24. Early style had one (1) wire, (RED) connected to the bottom of
the solenoid. The current style has a two (2) wire connector (GRAY for solenoid & BLACK, for ground) on the side of the
solenoid. Some versions can only be removed using an automotive 1/2" tappet wrench
Fig. 25 - Solenoid Test
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