Tecumseh ECV100, ECV120, H22, H80, HH40 Technician's Handbook
...
TECUMSEH
T E C H N I C I A N ' S H A N D B O O K
This manual covers engine models:
ECV100 - 120, H22 - 80, HH40 - 70, HHM80, HM70 - 100,
HMSK70 - 110, HMXL70, HS40 - 50, HSK30 - 70, HSSK40 - 50,
HT30 - 35, HXL35, LAV30 - 50, LEV80 - 120, TNT100 - 120,
TVM125 - 220, TVXL170 - 220, TVS75 - 120, TVXL105 - 115,
V40 - 80, VH40 - 70, V60 - 70, VM70 - 100
Model numbers are located on the engine shroud.
3 TO 11 HP
4-CYCLE
L-HEAD
ENGINES
ENGINES & TRANSMISSIONS
CONTENTS
CHAPTER 1 GENERAL INFORMATION ......................................................................................................1
ENGINE IDENTIFICATION ............................................................................................................................1
INTERPRETATION OF MODEL NUMBER....................................................................................................1
SHORT BLOCKS ...........................................................................................................................................2
FUEL ..............................................................................................................................................................2
ENGINE OIL...................................................................................................................................................3
TUNE-UP PROCEDURE .............................................................................................................. .................3
STORAGE......................................................................................................................................................4
CHAPTER 2 AIR CLEANERS ......................................................................................................................5
GENERAL INFORMATION ............................................................................................................................5
OPERATION ..................................................................................................................................................5
COMPONENTS..............................................................................................................................................5
TROUBLESHOOTING OR TESTING ............................................................................................................5
SERVICE .......................................................................................................................................................6
DISASSEMBLY PROCEDURE ......................................................................................................................6
POLYURETHANE-TYPE FILTER ELEMENT ................................................................................................6
PAPER-TYPE FILTER ELEMENT .................................................................................................................6
CHAPTER 3 CARBURETORS AND FUEL SYSTEMS .................................................................................7
GENERAL INFORMATION ............................................................................................................................7
OPERATION ..................................................................................................................................................8
FUEL PRIMERS.............................................................................................................................................8
IMPULSE FUEL PUMPS................................................................................................................................9
FLOAT STYLE CARBURETORS ................................................................................................................... 9
DIAPHRAGM (PRESSURE DIFFERENTIAL) CARBURETORS....................................................................9
COMPONENTS............................................................................................................................................10
CARBURETOR IDENTIFICATION...............................................................................................................11
DUAL SYSTEM CARBURETORS................................................................................................................11
SERIES 1 CARBURETORS.........................................................................................................................11
SERIES 3 & 4 CARBURETORS ..................................................................................................................11
DIAPHRAGM CARBURETORS ...................................................................................................................11
SERIES 6 CARBURETORS 4-CYCLE.........................................................................................................12
SERIES 8 .....................................................................................................................................................12
SERIES 9 .....................................................................................................................................................12
SERIES 10 (EMISSION) ..............................................................................................................................12
SERIES 11 ...................................................................................................................................................12
SERIES 11 BRIDGED..................................................................................................................................13
NON-TECUMSEH CARBURETORS -- DELLORTO CARBURETOR.........................................................12
ENGINE TROUBLESHOOTING CHART .....................................................................................................13
CARBURETION TROUBLESHOOTING CHART.........................................................................................14
TESTING......................................................................................................................................................15
SERVICE .....................................................................................................................................................15
CARBURETOR PRE-SETS AND ADJUSTMENTS .....................................................................................15
FINAL ADJUSTMENTS (NON-EMISSION ENGINES).................................................................................16
NON-ADJUSTABLE CARBURETOR ...................................................................................................... .....16
DISASSEMBLY PROCEDURE ....................................................................................................................17
FLOAT STYLE CARBURETORS ........................................................................................................ .........17
DIAPHRAGM CARBURETORS ...................................................................................................................19
FLOAT ADJUSTING PROCEDURE.............................................................................................................19
INSPECTION ...............................................................................................................................................20
ASSEMBLY ....................................................................................................................... ...........................21
STANDARD SERVICE CARBURETORS ....................................................................................................24
CHAPTER 4 GOVERNORS AND LINKAGE...............................................................................................26
GENERAL INFORMATION ..........................................................................................................................26
OPERATION ................................................................................................................................................26
INTERNAL COMPONENTS (VARIOUS STYLES).......................................................................................26
TROUBLESHOOTING .................................................................................................................................26
ENGINE OVERSPEEDING ..........................................................................................................................27
ENGINE SURGING......................................................................................................................................27
C Tecumseh Products Company
1998
i
SERVICE .....................................................................................................................................................27
GOVERNOR ADJUSTMENT .......................................................................................................................27
GOVERNOR ADJUSTMENT PROCEDURE FOR SHORT BLOCK INSTALLATIONS ...............................27
GOVERNOR GEAR AND SHAFT SERVICE ...............................................................................................28
SPEED CONTROLS AND LINKAGE ...........................................................................................................29
CHAPTER 5 REWIND STARTERS .............................................................................................................35
GENERAL INFORMATION ..........................................................................................................................35
OPERATION ................................................................................................................................................35
COMPONENTS............................................................................................................................................35
SERVICE .....................................................................................................................................................35
ROPE SERVICE ..........................................................................................................................................35
RETAINER REPLACEMENT .......................................................................................................................36
STYLIZED REWIND STARTER (TVS, HM, TVM, TVXL), AND STAMPED STEEL STARTER
(HM, VM, TVM, TVXL).............................................................................................................................36
STYLIZED REWIND STARTER WITH PLASTIC RETAINER ......................................................................37
STANDARD STAMPED STEEL AND CAST ALUMINUM STARTER (HM, VM) ..........................................38
VERTICAL PULL STARTER HORIZONTAL ENGAGEMENT TYPE ...........................................................39
VERTICAL PULL STARTER VERTICAL ENGAGEMENT TYPE .................................................................40
CHAPTER 6 ELECTRICAL SYSTEMS .....................................................................................................42
GENERAL INFORMATION ..........................................................................................................................42
OPERATION ................................................................................................................................................42
STARTING CIRCUIT AND ELECTRIC STARTERS ....................................................................................42
CHARGING CIRCUIT ..................................................................................................................................42
CONVERTING ALTERNATING CURRENT TO DIRECT CURRENT ..........................................................43
HALF WAVE RECTIFIER SINGLE DIODE ..................................................................................................43
FULL WAVE RECTIFIER BRIDGE RECTIFIER...........................................................................................43
COMPONENTS............................................................................................................................................43
BATTERY.....................................................................................................................................................43
WIRING........................................................................................................................................................43
ELECTRICAL TERMS..................................................................................................................................44
BASIC CHECKS...........................................................................................................................................45
TROUBLESHOOTING ELECTRICAL STARTER CIRCUIT FLOW CHART ................................................46
TROUBLESHOOTING ELECTRICAL CHARGING CIRCUIT FLOW CHART..............................................47
TESTING PROCEDURE..............................................................................................................................48
STARTING CIRCUIT....................................................................................................................................48
CHARGING CIRCUIT ..................................................................................................................................48
VOLTAGE REGULATIONS..........................................................................................................................56
LOW OIL SHUTDOWN SWITCHES ............................................................................................................56
SERVICE .....................................................................................................................................................57
12 VOLT OR 120 VOLT ELECTRIC STARTERS WITH EXPOSED SHAFT ...............................................57
12 VOLT D.C. OR 120 VOLT A.C. ELECTRIC STARTERS WITH THE STARTER GEAR UNDER
THE CAP ASSEMBLY.............................................................................................................................57
INSPECTION ...............................................................................................................................................58
CHAPTER 7 FLYWHEEL BRAKE SYSTEMS.............................................................................................59
GENERAL INFORMATION ..........................................................................................................................59
OPERATION ................................................................................................................................................59
BOTTOM SURFACE SYSTEM ....................................................................................................................59
INSIDE EDGE SYSTEM ..............................................................................................................................60
COMPONENTS............................................................................................................................................60
SERVICE .....................................................................................................................................................61
FLYWHEEL REMOVAL ...............................................................................................................................61
BRAKE LEVER AND PAD ...........................................................................................................................61
IGNITION GOUNDOUT TERMINAL ............................................................................................................61
STARTER INTERLOCK SWITCH ....................................................................................................... ......... 62
CONTROL CABLE ....................................................................................................................................... 62
BRAKE BRACKET REPLACEMENT ...................................................................................................... .....62
CHAPTER 8 IGNITION ................................................................................................................................63
GENERAL INFORMATION ..........................................................................................................................63
OPERATION ................................................................................................................................................63
SOLID STATE IGNITION SYSTEM (CDI) ....................................................................................................63
MAGNETO IGNITION SYSTEM (POINTS) ..................................................................................................63
ii
IDENTIFICATION OF TECUMSEH IGNITION SYSTEMS ...........................................................................64
COMPONENTS............................................................................................................................................64
IGNITION TROUBLESHOOTING ................................................................................................................66
TESTING PROCEDURE..............................................................................................................................67
SERVICE .....................................................................................................................................................68
SPARK PLUG SERVICE.............................................................................................................................. 68
CONDITIONS CAUSING FREQUENT SPARK PLUG FOULING ................................................................68
IGNITION TIMING PROCEDURE ...................................................................................................... .......... 68
SERVICE TIPS.............................................................................................................................................71
CHAPTER 9 INTERNAL ENGINE AND CYLINDER ...................................................................................72
GENERAL INFORMATION ..........................................................................................................................72
OPERATION ................................................................................................................................................72
4-CYCLE ENGINE THEORY .......................................................................................................................72
LUBRICATION SYSTEMS ...........................................................................................................................73
COUNTERBALANCE SYSTEMS.................................................................................................................73
COMPONENTS............................................................................................................................................74
ENGINE OPERATION PROBLEMS.............................................................................................................75
TESTING...................................................................................................................................................... 77
ENGINE KNOCKS .......................................................................................................................................77
ENGINE OVERHEATS ................................................................................................................................77
SURGES OR RUNS UNEVENLY ................................................................................................................77
ENGINE MISFIRES......................................................................................................................................77
ENGINE VIBRATES EXCESSIVELY ...........................................................................................................78
BREATHER PASSING OIL ..........................................................................................................................78
EXCESSIVE OIL CONSUMPTION ...................................................................................................... ........78
LACKS POWER ...........................................................................................................................................78
SERVICE .....................................................................................................................................................79
DISASSEMBLY PROCEDURE ....................................................................................................................79
CYLINDERS.................................................................................................................................................81
CYLINDER HEADS......................................................................................................................................82
PISTONS, RINGS AND CONNECTING RODS ...........................................................................................82
CRANKSHAFTS AND CAMSHAFTS ...........................................................................................................84
VALVES .......................................................................................................................................................85
CRANKCASE BREATHERS ........................................................................................................................86
CYLINDER COVER, OIL SEAL, AND BEARING SERVICE ........................................................................87
CRANKSHAFT BEARING SERVICE ...........................................................................................................88
COUNTERBALANCE SERVICE ..................................................................................................................89
FLYWHEEL SERVICE .................................................................................................................................89
CHAPTER 10 ENGINE SPECIFICATIONS .................................................................................................90
FOUR CYCLE TORQUE SPECIFICATIONS ...............................................................................................91
ENGINE SPECIFICATIONS STANDARD POINT IGNITION .......................................................................93
SOLID STATE AND EXTERNAL IGNITION.................................................................................................97
CHAPTER 11 EDUCATION MATERIALS AND TOOLS...........................................................................102
DECIMAL / FRACTION CONVERSIONS................................................................................................. .. 105
SEARS CRAFTSMAN CROSS REFERENCE SUPPLEMENT INCLUDED IN BACK OF BOOK
iii
CHAPTER 1 GENERAL INFORMATION
ENGINE IDENTIFICATION
Tecumseh engine model, specification, and serial
numbers or (date of manufacture, DOM) are stamped
into the blower housing or located on a decal on the
engine in locations as illustrated (diag. 1 & 2).
NOTE: On some LEV engines, a cover bezel must be
removed to provide access to the identification decal
(diag. 1).
The engine identification decal also provides the
applicable warranty code and oil recommendations (diag.
3).
Emissionized engines that meet the California Air
Resource Board (C.A.R.B.) or the Environmental
Protection Agency (E.P.A.) standards will include
additional required engine information on the engine decal
(diag. 3).
INTERPRETATION OF MODEL NUMBER
The first letter designation in a model number indicates
basic type of engine.
V - Vertical Shaft
LAV - Lightweight Aluminum Vertical
VM - Vertical Medium Frame
TVM - Tecumseh Vertical (Medium Frame)
VH - Vertical Heavy Duty (Cast Iron)
TVS - Tecumseh Vertical Styled
TNT - Toro N’ Tecumseh
ECV - Exclusive Craftsman Vertical
TVXL - Tecumseh Vertical Extra Life
LEV - Low Emissions Vertical
H - Horizontal Shaft
HS - Horizontal Small Frame
HM - Horizontal Medium Frame
HHM - Horizontal Heavy Duty (Cast Iron) Medium Frame
HH - Horizontal Heavy Duty (Cast Iron)
ECH - Exclusive Craftsman Horizontal
HSK - Horizontal Snow King
COVER BEZEL
MODEL AND
D.O.M. NUMBER
DECAL
LOCATED
UNDER COVER
(IF SO EQUIPPED)
PRESS IN AND LIFT
HERE TO RELEASE
COVER
Ç
1
HS50 67355H SER 4091D
2
1
The number designations following the letters indicate
the horsepower or cubic inch displacement.
The number following the model number is the
specification number. The last three numbers of the
specification number indicate a variation to the basic
engine specification.
The serial number or D.O.M. indicates the production
date.
Using model LEV115-57010B, serial 8105C as an
example, interpretation is as follows:
LEV115-57010B is the model and specification number
LEV Low Emissions Vertical
115 Indicates a 11.5 cubic inch displacement
57010B is the specification number used for properly
identifying the parts of the engine
8105C is the serial number or D.O.M. (Date of
Manufacture)
8 first digit is the year of manufacture (1998)
105 indicates calendar day of that year (105th day
or April 15, 1998)
C represents the line and shift on which the
engine was built at the factory.
FUEL REGULAR UNLEADED
OIL, SAE 30 (BELOW 32oF SAE 5W30)
LEV115 57010B (D)
STP185U1G1RA
8105C
THIS ENGINE MEETS 1995-1998
CALIF. EMISSION REGULATOR FOR
ULGE ENGINES AS APPLICBLE
FUEL: REGULAR UNLEADED OIL: USE SEA30
LEV115 57010B (D)
STP185U1G1RA
8105C
Engine Family: Engine Tracking Information
3
SHORT BLOCKS
SHORT BLOCK IDENTIFICATION TAG
New short blocks are identified by a tag marked S.B.H.
(Short Block Horizontal) or S.B.V. (Short Block Vertical).
Original model identification numbers of an engine should
SBV OR SBH IDENTIFICATION NUMBER
always be transferred to a new short block for correct
parts identification (diag. 4).
THIS SYMBOL POINTS OUT IMPORTANT
SAFETY INSTRUCTIONS WHICH IF NOT
SBV-2316
SER 4291
FOLLOWED COULD ENDANGER THE
PERSONAL SAFETY OF YOURSELF AND
OTHERS. FOLLOW ALL INSTRUCTIONS.
SERIAL NUMBER
4
FUEL
Tecumseh strongly recommends the use of fresh clean unleaded regular gasoline in all engines. Unleaded gasoline
burns cleaner, extends engine life and promotes better starting by reducing build-up of combustion chamber deposits.
REFORMULATED AND OXYGENATED FUELS
Reformulated fuels containing no more than 10% Ethanol, 15% MTBE, 15% ETBE or premium gasoline can be used
if unleaded regular gasoline is not available. Leaded fuel may be used in countries where unleaded fuel is not available.
NEVER USE FUEL CONTAINING METHANOL.
2
ENGINE OIL
Use a clean, high quality detergent oil. Be sure original container is marked: A.P.I. service SF thru SJ. The use of
multigrade oil may increase oil consumption under high temperature, high load applications.
NOTE: DO NOT USE SAE10W40 OIL.
For summer (above 32°F, 0oC) use SAE 30 oil part # 730225 (1 quart, .946 liter container) in high temperature, high
load applications.
S.A.E.10W30 is an acceptable substitute.
For winter (below 32°F, 0oC) use S.A.E. 5W30 oil part # 730226 (1 quart, .946 liter container)
S.A.E.10W is an acceptable substitute.
S.A.E. 0W30 should only be used when ambient temperature is below 0oF, -18oC.
CAPACITIES: EUROPA MODELS
Engine Model Oz. mL. Oz. mL.
LAV30-50, TVS75-120, LEV80-120 21 630 Vantage 21 630
ECV100-120, TNT100-120 21 630 Prisma 21 630
V & VH50, 60, 70 27 810 Synergy 21 630
TVM 125, 140 27 810 Synergy "55" 27 810
TVM & TVXL 170, 195, 220 32 960 Spectra 21 630
VM70, 80, 100 32 960 Futura 21 630
VH100 50 1500 Centura 21 630
H & HSK30, 35, HS & HSSK40, 50 21 630 HTL 21 630
H, HH & HSK50, 60, 70 19 570 BVS 21 630
HM & HMSK70, 80, 100 26 720 BH Series 21 630
Geo Tech Series 35-50 21 630
Oil Change Intervals. Change the oil after the first two (2) hours of operation and every 25 hours thereafter, or more
often if operated under dusty or dirty conditions, extreme temperature, or high load conditions.
Oil Check. Check the oil each time the equipment is used or every 5 hours. Position the equipment so the engine is
level when checking the oil.
CAUTION: REMOVE THE SPARK PLUG WIRE BEFORE DOING ANY SERVICE WORK ON THE ENGINE.
Oil Change Procedure: Locate the oil drain plug. On some units this plug is located below the deck through the
bottom of the mounting flange. Other units drain at the base of the engine above the deck or frame. If access to the
drain plug is restricted by the equipment it may be necessary to drain the oil by tipping the mower in a position that
would allow the oil to drain out of the fill tube.
On units that the drain plug is accessible, remove the plug and allow the oil to drain into a proper receptacle. Always
make sure that drain oil is disposed of properly.
Once the oil is drained, reinstall the plug and fill the engine with new oil to the proper capacity.
TUNE-UP PROCEDURE.
The following is a minor tune-up procedure. When this procedure is completed, the engine should operate properly.
Further repairs may be necessary if the engine's performance remains poor.
CAUTION: REMOVE THE SPARK PLUG WIRE BEFORE DOING ANY SERVICE WORK ON THE ENGINE.
1. Service or replace the air cleaner as needed.
2. Inspect the level and condition of the oil and change or add oil as required.
3. Remove the blower housing and clean all dirt, grass or debris from the intake screen, cylinder head, cylinder
cooling fins, carburetor, governor levers and linkage.
4. Make sure the fuel tank, fuel filter and fuel line are clean. Replace any worn or damaged governor springs or
linkage. Make the proper governor adjustments and carburetor presets where required.
3
5. When replacing the spark plug, consult the parts breakdown for the proper spark plug to be used in the engine
being serviced. Set the spark plug gap to .030" (.762 mm) and install the spark plug in the engine. Tighten the
spark plug to 15 foot pounds of torque (20.4 Nm). If a torque wrench isn’t available, screw the spark plug in as far
as possible by hand, and use a spark plug wrench to turn the spark plug 1/8 to 1/4 turn further if using the old spark
plug, or 1/2 turn further if using a new spark plug.
6. Make sure all ignition wires are free of abrasions or breaks and are properly routed so they will not rub on the
flywheel.
7. Properly reinstall the blower housing, gas tank, fuel line and air cleaner assembly if removed.
8. Make sure all remote cables are properly adjusted for proper operation. See chapter 4 under "Speed Controls and
Linkage".
9. Reinstall the spark plug wire, add fuel and oil as necessary, and start the engine.
STORAGE: (IF THE ENGINE IS TO BE UNUSED FOR 30 DAYS OR MORE)
CAUTION: NEVER STORE THE ENGINE WITH FUEL IN THE TANK INDOORS , IN ENCLOSED POORLY
VENTILATED AREAS WHERE FUEL FUMES MAY REACH AN OPEN FLAME, SPARK OR PILOT LIGHT
AS ON A FURNACE, WATER HEATER, CLOTHES DRYER OR OTHER GAS APPLIANCE.
Gasoline can become stale in less than 30 days and form deposits that can impede proper fuel flow and engine
operation. To prevent deposits from forming, all gasoline must be removed from the fuel tank and the carburetor. An
acceptable alternative to removing all gasoline is adding a fuel stabilizer to the gasoline. Fuel stabilizer (such as
Tecumseh's Part No. 730245) is added to the fuel tank or storage container. Always follow the mix ratio found on the
stabilizer container. Run the engine at least 10 minutes after adding the stabilizer to allow it to reach the carburetor.
CAUTION: THE USE OF SOME ANTI-ICING ADDITIVES MAY CREATE A METHANOL FUEL BLEND. DO
NOT USE ADDITIVES THAT CONTAIN METHANOL. FUEL CONDITIONERS THAT CONTAIN ISOPROPYL
ALCOHOL IS RECOMMENDED.
Draining the Fuel System:
CAUTION: DRAIN THE FUEL INTO AN APPROVED CONTAINER OUTDOORS, AND AWAY FROM ANY
OPEN FLAME OR COMBUSTION SOURCE. BE SURE THE ENGINE IS COOL.
1. Remove all gasoline from the fuel tank by running the engine until the engine stops, or by draining the fuel tank by
removing the fuel line at the carburetor or fuel tank. Be careful not to damage the fuel line, fittings, or fuel tank.
2. Drain the carburetor by pressing upward on the bowl drain (if equipped) which is located on the bottom of the
carburetor bowl. On carburetors without a bowl drain, the carburetor may be drained by loosening the bowl nut on
the bottom carburetor one full turn. Allow to completely drain and retighten the bowl nut being careful not to
damage the bowl gasket when tightening.
3. If "Gasohol" has been used, complete the above procedure and then put one half pint of unleaded gasoline into
the fuel tank and repeat the above procedure. If Gasohol is allowed to remain in the fuel system during storage,
the alcohol content will cause rubber gaskets and seals to deteriorate.
Change Oil: If the oil has not been changed recently, this is a good time to do it.
Oil Cylinder Bore:
1. Disconnect the spark plug wire and ground the wire to the engine. Remove the spark plug and put 1/2 ounce
(14 ml) of clean engine oil into the spark plug hole.
2. Cover the spark plug hole with a shop towel.
3. Crank the engine over slowly several times.
CAUTION: AVOID SPRAY FROM SPARK PLUG HOLE WHEN SLOWLY CRANKING ENGINE OVER.
4. Install the spark plug and connect the spark plug wire.
Clean Engine: Remove the blower housing and clean all dirt, grass or debris from the intake screen, cylinder head,
cylinder cooling fins, carburetor, governor levers and linkage.
4
CHAPTER 2 AIR CLEANERS
GENERAL INFORMA TION
The air cleaner is the device used to eliminate dust and dirt
from the air supply . Filtered air is necessary to assure that
abrasive particles are removed before entering the carburetor
and combustion chamber. Dirt allowed into the engine will
quickly wear the internal components and shorten the life
of the engine.
Tecumseh engines use either a polyurethane or a papertype air filter system. A polyurethane pre-cleaner or a flocked
screen may be used in conjunction with the main filter.
Snow King® engines do not use an air filter.
Extremely dirty conditions may require more frequent filter
cleaning or replacement.
OPERATION
The outer cover encapsulates the air filter element(s) and
prevents large particles from entering the filter box. Air is
filtered through the pre-cleaner or flocked screen (if equipped)
and the polyurethane or paper filter element. Pre-cleaners
or flocked screens provide additional air cleaning capacity .
In T ecumseh's Kleen Aire® system, air is drawn in through
a rotating screen or recoil cover to be centrifugally cleaned
by the flywheel before the air is drawn into the air filter.
COMPONENTS
The cover holds the filter element and prevents large debris
from entering the filter element.
The polyurethane wrap pre-filter is used on XL or XL/C
engine models with paper filter elements.
(diag 1 & 2)
COVER
POLYURETHANE
WRAP
SEALING NUTS
PAPER
ELEMENT
AIR CLEANER
BODY
1
The paper or polyurethane filter element is the main
filter to trap dust and dirt. Dry-type paper elements have
treated paper folded for increased surface area and rubberlike sealing edges. The polyurethane filter uses an oil film
to trap fine particles found in dust.
The flocked screen is used as an additional filter on XL or
XL/C engine models that use a polyurethane filter element.
TROUBLESHOOTING OR TESTING
If the engine's performance is unsatisfactory (needs
excessive carburetor adjustments, starts smoking
abnormally , loses power), the first engine component to be
checked is the air cleaner. A dirt restricted or an oil soaked
element will cause noticeable performance problems. A
polyurethane element may be cleaned following the service
procedure listed under "Service" in this chapter. A papertype air filter should only be replaced. A paper-type element
cannot have an oil film present on the paper. Follow the
procedure listed in the "Service" section of this chapter for
replacement. Re-try the engine after filter replacement or
service. If the problem persists after filter service, see
Chapter 9 under "Engine Operation Problems" for additional
causes.
COVER
AIR CLEANER
BODY
FOAM
ELEMENT
FLOCKED SCREEN
2
5
SERVICE
Service on the polyurethane element (cleaning and oiling) is recommended every three months or every twenty five
operating hours, whichever comes first. Extremely dirty or dusty conditions may require daily cleanings.
The paper filter element should be replaced at least once a year or more frequently if operated in dusty or dirty conditions.
NOTE: NEVER RUN THE ENGINE WITHOUT THE COMPLETE AIR CLEANER ASSEMBLY INSTALLED ON THE
ENGINE. AL WA YS REPLACE THE FIL TER ELEMENT WITH THE PROPER TECUMSEH ORIGINAL REPLACEMENT
PART.
DISASSEMBLY PROCEDURE
1. Unlock the tabs or remove the screws, wingnuts or
snaps holding the air cleaner cover in place.
2. Remove the hex nuts holding the element down if
equipped. New nuts are supplied with a new filter and
MUST be used for proper sealing.
3. Clean the excess contaminants out of the air cleaner
body before removing the old element.
4. Remove the old element and the polyurethane pre-
cleaner if equipped.
5. On air cleaners that use a flocked screen under the
polyurethane element, remove the air cleaner assembly
from the carburetor before removing the flocked screen.
This prevents dirt from entering the carburetor (diag 3).
FOAM
ELEMENT
1/2" (12.7 mm)
FOAM
WITH FLOCKED
SCREEN
ATTACHED
6. Clean the inside of the cover and body , remove the old
gasket between the carburetor and the air cleaner
assembly.
7. Reinstall the air cleaner assembly using a new gasket.
8. Use the reverse procedure for reassembly. When
installing the foam polyurethane pre-cleaner, make sure
the seam is installed to the outside to prevent gaps
AIR CLEANER
BODY
between the paper element and the pre-cleaner.
3
POLYURETHANE-TYPE FILTER ELEMENT
This type of air filter can be serviced when restricted with dust or dirt. Wash the filter or pre-cleaner in a liquid detergent
and water solution until all the dirt is removed. Rinse in clear water to remove the detergent solution. Squeeze the
element (do not twist) to remove the excess water. W rap the element in a clean cloth and squeeze it (do not twist) until
completely dry .
Re-oil the element by applying engine oil and squeezing it vigorously to distribute the oil. Roll the element in a cloth and
squeeze it (do not twist) to remove the excess oil.
Clean the air cleaner housing and cover being careful not to allow dirt to fall into the carburetor or intake pipe.
PAPER -TYPE FILTER ELEMENT
Paper type air filter elements can only be serviced by replacement. Do not attempt to clean a paper filter element.
6
CHAPTER 3 CARBURETORS AND FUEL SYSTEMS
GENERAL INFORMA TION
Tecumseh uses two basic types of carburetors, float and diaphragm type carburetors. Float type carburetors use a
hollow float to maintain the operating level of fuel in the carburetor. Diaphragm type carburetors use a rubber-like diaphragm.
One side is exposed to intake manifold pressure and the other side to atmospheric pressure. The diaphragm provides the
same basic function (maintaining the proper fuel level in the carburetor) as the float.
An advantage of the diaphragm carburetor over the float style is that the diaphragm carburetor will allow the engine to
operate at a greater degree of tiltability .
T ecumseh carburetors are identified by a manufacturing number and date code stamped on the carburetor as illustrated
(diag. 1).
When servicing carburetors, use the engine model and
specification number to obtain the correct carburetor part
number. An alternate method of finding the correct
carburetor part number is to use the manufacturing number
stamped on the carburetor and convert this number to a
part number. In the carburetor section of the Master Parts
ALTERNATE LOCATION
FOR MANUFACTURING
NUMBER
8
9
4
F
5
Manual, Microfiche Catalog or computer parts look-up
system, a cross reference chart will convert a carburetor
manufacturing number to a T ecumseh part number .
Complete carburetor replacement may be accomplished
89 4F5
with a standard service carburetor. A standard service
carburetor is a basic carburetor that may require the use
of original carburetor parts or additional new parts to adapt
to the specification. An instruction sheet is provided with
the new service carburetor or see “SERVICE” in this chapter .
MANUFACTURING
NUMBER
CARBURETOR
DATE CODE
1
CAUTION: DRAIN THE FUEL INTO AN APPROVED CONT AINER OUTDOORS, AND AW A Y FROM ANY OPEN
FLAME OR COMBUSTION SOURCE. BE SURE THE ENGINE IS COOL.
NOTE: Todays fuels can cause many problems in an engines performance, due to the fuels quality and short shelf life.
Always check fuel as a primary cause of engine performance.
1. Remove the air filter, heater box, or air cleaner assembly if applicable to visually check that the choke shutter
completely closes or check to see if fuel comes out of the main nozzle during priming.
2. If the fuel flow from the tank is adequate and no fuel is evident during priming, the carburetor will need to be
removed for service. See “Service” in this chapter or consult the “Carburetion Troubleshooting” chart to diagnose
carburetor symptoms. Improper fuel flow indicates the fuel, fuel line, filter or tank require cleaning or replacement.
3. Check the engine compression using a commercially available compression tester and follow the tester’s
recommended procedure. Low compression, a dry spark plug, adequate fuel flow, and a known good functional
carburetor indicates an internal engine problem exists. See under “Troubleshooting.”
4. A wet spark plug indicates fuel is being supplied by the carburetor. The engine may be flooded by a restricted
air filter, carbon shorted or defective spark plug, excessive choking or over priming, improperly adjusted or
defective carburetor. With the spark plug removed and a shop towel over the spark plug hole, turn the engine
over slowly 3 or 4 times to remove excess gasoline from the engine cylinder.
CAUTION: KEEP ALL COMBUSTIVE SOURCES AWAY. AVOID THE SPRAY FROM THE SPARK PLUG
HOLE WHEN CRANKING THE ENGINE OVER.
5. Replace the air filter if restricted or oil soaked. Replace the spark plug if questionable. Install the spark plug and
high tension lead and try to start the engine.
6. If the engine floods and fails to start, the carburetor will require service. See the proceeding “Carburetion
Troubleshooting” chart for additional causes. If the carburetor is functioning properly the problem may be ignition
timing related. See “Troubleshooting" under "Ignition”.
7
OPERATION
In the “CHOKE” or “START” position, the choke shutter is closed and the only air entering the engine enters through
openings around the shutter. As the engine starts to rotate, downward piston travel creates a low air pressure area (or
vacuum) above the piston. Higher pressure (atmospheric) air rushes into the engine and fills this low pressure area. Since
the majority of the air passage is blocked by the choke shutter, a relatively small quantity of air enters the carburetor at
an increased speed. The main nozzle and both idle fuel discharge ports are supplying fuel due to the low air pressure in
the engine intake. Maximum fuel flow through the carburetor orifices combined with the reduced quantity of air that
passes through the carburetor, make a very rich fuel mixture which is needed to start a cold engine.
At engine IDLE speed, a relatively small amount of fuel is required to operate the engine. The throttle is almost completely
closed. Fuel is supplied through the primary idle-fuel discharge orifice.
NOTE: Dual system carburetors do not have an idle circuit.
During INTERMEDIA TE engine operation, a second orifice is uncovered as the throttle shutter opens, and more fuel is
allowed to mix with the air flowing into the engine.
During HIGH SPEED engine operation, the throttle shutter is fully opened. Air flows through the carburetor at high speed.
The venturi, which decreases the size of the air passage through the carburetor, further accelerates the air flow . This high
speed movement of the air decreases the air pressure at the main nozzle opening. Fuel is forced out the main nozzle
opening due to the difference in the air pressure on the fuel in the carburetor bowl and the reduced air pressure at the main
nozzle opening.
For the fuel to flow, the carburetor bowl must be either
vented externally or internally . Some internally vented float
style carburetors use a tygon tube and a vent within the air
intake. This tube must be present for the carburetor to
operate properly (diag. 2).
Air is bled into the main nozzle and through the air bleed
located in the air horn. This mixes the fuel and air prior to
the fuel leaving the main nozzle. Atomization occurs as
the fuel mixture contacts the fast moving air stream. This
mist then flows into the intake of the engine.
FUEL PRIMERS
Primers may be mounted remotely or as an integral part of
the carburetor. The basic function of the primer is to supply
a charge of air to the carburetor main well, or carburetor
bowl. On diaphragm carburetors it displaces fuel directly
into the carburetor venturi. This displaced fuel provides a
rich mixture necessary for engines to start easily on the
first or second attempt (diag. 3 & 4).
Primers must be vented either internally (a passage in the
carburetor air horn prior to the venturi) or externally (through
a hole in the primer bulb). The vent allows air to fill the
primer bulb after the primer bulb is released. On diaphragm
carburetors a one way valve in the body prevents the fuel
from being forced back into the fuel tank.
Two different methods are used to prime float style
carburetors, leg prime and bowl prime. The leg prime
system is used only on the dual system carburetor. Air is
forced into the center leg of the carburetor, which then forces
an enriched mixture of fuel up the main nozzle. The bowl
prime method is used on Series 6, 8, 9 and 10 carburetors
and is distinguished by a stepped or hour glass shaped
primer bulb. A good seal of the primer bulbs center lip is
critical to assure that a full charge of air reaches the bowl.
Also critical is a tight seal around the float bowl.
TYGON TUBE
LOCATION
BOWL PRIME
PRIMER BULB
3
PRIMER BULB
MAIN NOZZLE
EMULSION
TUBE
MAIN JET
2
4
NOTE: Never re-use a bowl gasket.
8
5
IMPULSE FUEL PUMPS
Impulse fuel pumps may either be mounted externally onto
the carburetor fuel inlet or remotely mounted. These pumps
are connected in the fuel line between the fuel supply and
the carburetor or directly to the fuel inlet.
Impulse fuel pumps are operated by crankcase impulses
created by the up and down movement of the piston. A
hose called a pulse line connects the fuel pump diaphragm
chamber to the crankcase and transmits these impulses
to the pump diaphragm. The impulses actuate the
diaphragm and flap valves to lift the fuel from the fuel tank
to the carburetor (diag. 6).
6
FLOAT STYLE CARBURETORS
A float is used to maintain the operating volume of fuel in
the carburetor bowl. As the fuel is used by the engine, the
fuel volume in the carburetor bowl drops and the float moves
downward. This allows the inlet needle valve to move off
the sealing seat. Fuel flows by gravity or a pulse pump into
the fuel bowl. As the fuel volume in the bowl again rises, it
raises the float. This upward float motion moves the inlet
needle valve to the closed position. When the needle
contacts the seat, the fuel flow is stopped. The tapered
end of the inlet needle varies the fuel flow rate so that the
fuel volume in the carburetor bowl will remain constant (diag.
7). The float height is set according to the service procedure.
DIAPHRAGM (PRESSURE DIFFERENTIAL)
CARBURETORS
This type of carburetor uses a rubber-like diaphragm which
is exposed to intake manifold pressure on one side and to
atmospheric pressure on the other. Tecumseh diaphragm
carburetors use the diaphragm as a metering device. As
the intake manifold pressure decreases due to downward
piston travel, the atmospheric pressure on the vented side
of the diaphragm moves the diaphragm against the inlet
needle. The diaphragm movement overcomes the spring
tension on the inlet needle and moves the inlet needle off
the seat. This permits the fuel to flow through the inlet
valve to maintain the correct fuel volume in the fuel chamber.
The inlet needle return spring closes the inlet valve when
the pressure on the diaphragm equalizes or a pressure
higher than atmospheric exists on the intake side (upward
piston travel). The diaphragm meters a correct fuel volume
in the fuel chamber to be delivered to the mixing passages
and discharge ports (diag. 8).
IDLE AND
PROGRESSION
HOLES
THROTTLE
SHUTTER
IDLE
ADJUSTMENT
MAIN NOZZLE
EMULSION
TUBE
THROTTLE
SHUTTER
IDLE
ADJUSTMENT
IDLE AIR
BLEED
MAIN
ADJUSTMENT
CHECK BALL
MAIN AIR
BLEED
CHOKE
SHUTTER
INLET NEEDLE
AND SEAT
FLOAT
7
CHOKE
SHUTTER
NEEDLE AND
SEAT ASSEMBLY
A main or idle adjustment needle may be replaced by an
internally fixed jet on some models.
The main nozzle contains a ball check valve. The main
purpose of this ball check is to eliminate air being drawn
down the main nozzle during idle speeds and leaning the
idle mixture.
An advantage of the diaphragm carburetor over the float
system is that the diaphragm carburetor increases the angle
that the engine may be operated at.
MAIN
ADJUSTMENT
DIAPHRAGM
8
9
COMPONENTS
Loosen screw until it just clears throttle
lever, then turn screw in 1 turn.
Place detent reference mark to proper
location.
Check spring for return action and binding.
Remove welch plug and blow air
through air passages.
Remove adjustment screw. T o adjust
20° slant engines, the engine must be
mounted in its normal 20° slant position.
Check ball is not serviceable on some
models.
*NON METALLIC ITEMS - CAN BE DAMAGED
BY HARSH CARBURETOR CLEANERS
Blow air through passage.
Check shaft for looseness or binding.
Shutter must be positioned with detent
reference marks on top parallel with
shaft and to the right or 3 o'clock position.
Check spring for return action
and binding.
Remove idle adjustment screw. Check
needle tip and condition of "O" ring.
Remove welch plug and blow out all
passages.
NOTE: On models which have metering
rods, do not install idle adjustment screw
with carburetors upside down, as pin
will obstruct movement of adjustment
screw causing damage
*NON METALLIC ITEMS - CAN BE DAMAGED
BY HARSH CARBURETOR CLEANERS
IDLE AND INTERMEDIATE
AIR BLEED
THROTTLE SHAFT AND LEVER
THROTTLE SHUTTER
DETENT
REFERENCE MARK
THROTTLE SHAFT
RETURN SPRING
IDLE AND INTERMEDIATE
ORIFICES
IDLE AND INTERMEDIATE
FUEL CHAMBER (COVERED
WITH WELCH PLUG)
IDLE AND INTERMEDIATE
FUEL MIXTURE PASSAGE
*IDLE ADJUSTMENT SCREW
AND "O" RING
ATMOSPHERIC VENT
SOFT BAFFLE PLUG
IDLE AND INTERMEDIATE
FUEL TRANSFER PASSAGE
METERING ROD OR PIN IN
FUEL TRANSFER PASSAGE
BALL PLUG
CUP PLUG
IDLE AND INTERMEDIATE
FUEL TRANSFER PASSAGE
IDLE AND MAIN FUEL PICK UP ORFICE
10
IDLE SPEED ADJUSTMENT SCREW
THROTTLE SHAFT AND LEVER
DETENT REFERENCE MARK
ON THROTTLE SHUTTER
THROTTLE SHUTTER
THROTTLE SHAFT
RETURN SPRING
IDLE PROGRESSION
HOLE
IDLE AIR BLEED
*IDLE MIXTURE
ADJUSTMENT
SCREW AND "O"
RING (If Present)
*MAIN MIXTURE
ADJUSTMENT
SCREW AND "O"
RING (If Present)
WELCH PLUG (If Present)
*MAIN NOZZLE CHECK BALL (If Present)
IDLE
(DO NOT REMOVE)
CHOKE SHAFT AND LEVER
CHOKE SHUTTER
MAIN NOZZLE
*INLET
FITTING
SCREEN
*INLET
FITTING
*INLET SEAT
GASKET
*INLET NEEDLE
SEAT AND
SPRING
ASSEMBLY
*DIAPHRAGM GASKET
*DIAPHRAGM
ATMOSPHERIC VENT HOLE
IDLE SPEED ADJUSTMENT
MAIN NOZZLE
(EMULSION TUBE)
CHOKE SHAFT
AND LEVER
CHOKE PLATE
HIGH SPEED
AIR BLEED
INLET
FITTING
*INLET NEEDLE
AND SEAT
*FLOAT BOWL
GASKET
FLOAT
SHAFT
NUT AND MAIN ADJUSTMENT SEAT
*MAIN ADJUSTMENT SCREW AND
"O" RING SEAL
INLET
NEEDLE CLIP
(If Present)
IDLE FUEL TRANSFER PASSAGE
AND ANNULAR GROOVE
FLOAT
FLOAT BOWL
*GASKET
Check shaft for binding. Position shutter opening towards inlet fitting side or
air horn.
Blow air through passage.
Part of inlet fitting. If fuel is restricted,
clean or replace fitting.
Bulb primer models have Viton* one
way valve, in or behind fitting.
Remove and replace.
Proper installation of assembly is important.
Gasket and diaphragm sequence may
be reversed on some models. Head of
rivet must touch inlet needle. Rivet is
hooked into inlet needle control lever on
some models.
Hole must be clean. On models with
bulb primer, vent hole is very small and
is located off center.
Loosen screw until it just clears throttle
lever, then turn screw in one turn.
Removable on emission carbs. nonmetallic only.
Check shaft for binding position opening to bottom of air horn.
Blow air through passage. Do not remove restrictor if present.
Proper installation is important.
Replace.
Must hook over float tab.
Check float for leaks or dents. Clean
bowl and adjust float level position gasket or gaskets.
If the carburetor is used on a 20° slant
engine, the engine must be in its normal
20° slanted position for adjustment.
Check needle for damage and "O" ring
for cracks. Clean all passages in nut
with compressed air.
9
10
CARBURETOR IDENTIFICATION
Tecumseh has a variety of carburetors. To help identify
these carburetors here are some simple procedures to
follow.
DUAL SYSTEM CARBURETORS
The easiest way to identify the dual system carburetor is
by the presence of a large primer bulb located on the side
of the carburetor. The absence of adjustment needles help
to identify the carb as well. The dual system carburetor is
used on 4-cycle vertical crankshaft rotary mower engines.
(diag. 1 1).
SERIES 1 CARBURETORS
Series 1 carburetors come in a variety of styles. They are
used on both 2 and 4 cycle vertical and horizontal shaft
engines in the 2 through 7 h.p. range. It is a float style
carburetor with a smaller venturi than the Series 3 and 4
carburetors. Some will have an adjustable idle and main
and others will have a fixed main with an adjustable idle.
There are also some fixed speed applications that will only
have a fixed main system and the idle system will not be
drilled. (diag. 12).
11
12
NOTE: Emissionized carburetors will have a fixed jet.
SERIES 3 & SERIES 4 CARBURETORS
Series 3 and 4 carburetors are generally used on 8 through
12.5 horsepower 4-cycle engines. The venturi size of these
carburetors are larger than Series 1 and Dual System
Carburetors. The quickest way to identify these carburetors
is by the presence of bosses on each side of the idle mixture
screw. To identify the Series 3 from a Series 4, view the
carburetor from the throttle end. The Series 3 has (1) screw
securing the throttle plate and the Series 4 uses (2) screws.
(diag. 13 - 15)
DIAPHRAGM CARBURETORS
The diaphragm carburetors are unique. These carburetors
can be operated at a more severe angle than float style
carburetors. They still require that the fuel supply be located
in a position that allows it to be gravity fed. Its most
distinctive feature is the lack of a fuel bowl. (diag. 16).
BOSSES
SERIES 3
14
SERIES 4
13
15
NOTE: Emissionized carburetors will have a fixed jet.
16
11
SERIES 6 CARBURETORS 4-CYCLE
Series 6 carburetors are used on 2 and 4-cycle engines.
They have a larger venturi than the dual system carburetor
and use a simple fixed idle system. Series 6 carburetors
used on both vertical and horizontal applications are
nonadjustable. The 4 cycle version pictured has a stepped
primer bulb. (diag. 17).
SERIES 8
The Series 8 carburetor has both a fixed main and idle
circuit. The fixed idle system uses a restricted jet that
meters the fuel. The idle restrictor jet will be capped to
prevent access unless removed. The fixed main jet is part
of the bowl nut. A ball plug is visible from the bottom, which
seals the metering passage. This carburetor also has a
serviceable main nozzle emulsion tube. It also has a
stepped primer bulb to assist in starting. (diag. 18)
SERIES 9
GREY
CAPPED FIXED
JET
MIXING WELL
CAST BUT NOT
MACHINED
17
18
The Series 9 carburetor uses the same body as the Series
8 but has a simple fixed idle system, identical to the one
used on the Series 6 carburetor. It has the idle discharge
port located at the 7 o'clock position on the throttle end of
the carburetor. Identify this carburetor by the stepped primer
bulb, the presence of a non-drilled idle mixing well and a
serviceable main nozzle emulsion tube. (diag. 19)
SERIES 10 (EMISSION)
The Series 10 carburetor is identical to the Series 8
carburetor with the addition of a choke to assist in cold
weather starts. It also has a fixed idle and main. The idle
restrictor jet is capped to prevent access unless the cap is
removed. The fixed main jet is part of the bowl nut. A ball
plug is visible from the bottom, which seals the metering
passage. This carburetor also has a serviceable main nozzle
emulsion tube and a stepped primer bulb to assist in
starting. (diag. 20)
SERIES 11
The Series 11 carburetor is used on most LEV model
engines. This carburetor contains a patented autoenrichment system for improved starting and performance
of a cold engine. The system contains a fuel well that is
filled as part of the priming procedure and emptied as the
engine runs in the first minute. This added fuel provides
smooth operation of today’s emission grade engines. The
carburetor can be identified externally by the BLACK
colored restrictor cap (diag. 21). Internally the standard
Series 1 1 is identified by the plugged passage as shown.
IDLE JET
CAST BUT NOT
MACHINED
BLACK CAP
19
20
12
HOLE PLUGGED
21
SERIES 11 BRIDGED
Externally this carburetor looks identical to the standard
series 11 with the black restrictor cap. The difference is
internal through the addition of a second idle feed passage
with a restrictor as shown. This extra passage improves
run quality during light load engine operation (diag. 22).
BLACK CAP
ADDED
RESTRICTOR
NON-TECUMSEH CARBURETORS
DELLORTO CARBURETOR
The Dellorto carburetor is similar to the dual system
carburetor. It has no adjustments and has a primer assist
start. It has a noncorrosive float and the needle is viton
tipped, eliminating the viton seat found in the dual system
carburetor. The angle of the fuel inlet is adjustable and
attached to the carburetor body with a banjo bolt. This
carburetor is used on some TVS rotary lawnmower
engines.
ENGINE
TROUBLESHOOTING
Engine Will Not Start
Check For Spark
22
23
Wet Dry
Check If Spark Plug Is Wet or Dry
Defective Spark Plug Check Fuel Supply and Fuel
Cap Vent
Restricted Air Filter Restriction in Fuel System
(filter, screen)
Improper or Stale Fuel Carburetion Problem
Sheared or Partially Sheared
Flywheel Key Poor Compression
Carburetion Problems Due to
Flooding, Over Priming, etc.
Ignition System
13
AIR SYSTEM
PROBLEMS
CARBURETION
TROUBLESHOOTING
START IDLE ACCELERATE HIGH SPEED
Will
Not
Run at
High
Speed
Low
Power
Hunts at
High
Speed
Runs with
Needle
Closed
Hard
Starting
Fuel Leak
at
Carburetor
Engine
Floods
Will Not
Idle
Rich Idle
Idles with
Needle
Closed
Hunts Erratic
Idle
Idles
Fast Lean
Will Not
Accelerate
Over Rich
Acceleration
Hesitates
Engine
Overspeeds
Plugged Air Filter
Leaky Carburetor
Gasket
Throttle or Choke
Shafts Worn
Choke Not
Functioning
Properly
Plugged
Atmospheric Vent
Air Bleed
Restricted
Damaged or
Leaky "O" Rings
DIAPHRAGM
SYSTEM
PROBLEM
Damaged
Diaphragm
Stuck or Dirty Ball
Check
Diaphragm
Upside Down
Á
Á
Á
Á
Á
ÁÁ
Á
Á
Á
Á
Á
Á
ÁÁ
Á
Á
Á
Á
Á
Á
Á
Á
ÁÁ Á Á
Á
ÁÁ
Á
Á
ÁÁÁÁ
ÁÁ
Á
Á
Á
Á
Á
Á
Á
Á
FUEL SYSTEM
PROBLEM
Plugged Tank
Filter or Vent
Fuel Pick-up
Restricted
Idle Port
Restricted
Damaged
Adjustment
Needles
Incorrect Float
Height
Main Nozzle
Restricted
Dirty, Stuck
Needle and Seat
Fuel Inlet Plugged
14
Á
ÁÁ
Á
Á
Á
Á
Á
Á
Á
Á
ÁÁ
Á
Á
Á
Á
Á
Á
ÁÁ
ÁÁ
Á
Á
Á
ÁÁÁ
ÁÁ
ÁÁ
Á
Á
Á
Á
Á
Á
Á
Á
Á
Á
Á
Á
Á
TESTING
1. After repeated efforts to start the engine using the procedure listed in the operator’s manual fail, check for spark by
removing the high tension lead and the spark plug. Install a commercially available spark plug tester and check for
spark. If spark is evident and acceptable, proceed to step 2. If no or weak spark, see Chapter 8 under "T esting".
2. Visually inspect the spark plug for a wet condition indicating the presence of gasoline in the cylinder .
3. If the spark plug is dry, check for restrictions in the fuel system before the carburetor. If the spark plug is wet,
continue with step # 7. Check to see if the fuel cap vent is open. With a proper draining receptacle, remove the fuel
line clamp on the carburetor fuel inlet and pull the fuel line off the fitting to examine the fuel flow and fuel condition.
4. Remove the air cleaner element or air cleaner assembly to visually check that the choke shutter completely closes
or check to see if fuel comes out from the main nozzle during priming.
5. If the fuel flow is adequate and no fuel is evident during priming, the carburetor will need to be removed for service. See
“Service” in this chapter or consult the “Carburetion Troubleshooting” chart if other problems exist. Improper fuel flow
indicates the fuel, fuel line, filter or tank require cleaning or replacement.
6. Check the engine compression using a commercially available compression tester and follow the tester’s recommended
procedure. Low compression, a dry spark plug, adequate fuel flow, and a known good functional carburetor indicates
an internal engine problem exists. See Chapter 9 under “Engine Operation Problems.”
7. A wet spark plug indicates fuel is being supplied by the carburetor. The engine may be flooded by a restricted air filter ,
carbon shorted or defective spark plug, excessive choking or over priming, improperly adjusted or defective carburetor,
or the wrong ignition timing. With the spark plug removed and a shop towel over the spark plug hole, turn the engine
over slowly 3 or 4 times to remove excess gasoline from the engine cylinder.
CAUTION: KEEP ALL COMBUSTIVE SOURCES AWAY. AVOID THE SPRAY FROM THE SPARK PLUG
HOLE WHEN CRANKING THE ENGINE OVER.
8. Replace the air filter if restricted or oil soaked. Replace the spark plug if questionable. Install the spark plug and high
tension lead and retry starting the engine.
9. If the engine floods and fails to start, the carburetor may require service. See the preceding “Carburetion Troubleshooting”
chart for additional causes. If the carburetor is functioning properly the problem may be ignition timing related. See
Chapter 8 under “Ignition Troubleshooting.”
SERVICE
CARBURETOR PRE-SETS AND ADJUSTMENT
NOTE: EMISSION GRADE CARBURETORS HA VE FIXED IDLE AND MAIN JETS. THE ABSENCE OF THE ADJUSTING
SCREW INDICA TES A FIXED JET OR RESTRICTOR AND NO ADJUSTMENT IS NECESSARY . THE IDLE RESTRICTOR
ON AN EMISSIONS CARBURETOR APPEARS AS AN ADJUST ABLE SCREW. THIS IS NOT ADJUSTABLE AND
MUST REMAIN TIGHT FOR PROPER OPERA TION.
The idle on an emission is metered using a threaded
restrictor (see Illustration). Proper torque of this screw is
critical and should be torqued to 5-8 in. lbs. or .5 to 1 nm,
if not, it may vibrate loose. When the restrictor is placed in
the idle circuit passage it is capped with a tamper resistant
plastic cap. Tampering is considered the rejetting or
modification through resizing of the jet. If the jet is
removed for cleaning it must be recapped to prevent
tampering when it is re-installed.
IDLE RESTRICTOR
CAP
Before adjusting any mixture screws the necessary carburetor presets should be made. Check for the proper governor
adjustments as outlined in Chapter 4. Identify the correct carburetor model and manufacturer to find locations of the high
and low speed adjustment screws. Check the throttle control bracket for proper adjustment allowing a full choke shutter
position. See Chapter 4 under "Speed Controls and Linkage". Check to see if the normal maintenance procedures have
been performed (oil changed, fresh fuel, air filter replaced or clean). Consult microfiche card #30 to find the correct R.P .M.
settings for the engine, or consult Service Bulletin #107 for the revised safety specification for rotary type power lawn
mowers. Start the engine and allow it to warm to operating temperature. The carburetor can now be adjusted.
15
PRE-SETS AND ADJUSTMENTS
(TECUMSEH AND WALBRO
CARBURETORS)
NOTE: OVERTIGHTENING WILL DAMAGE THE T APER
PORTION OF THE NEEDLE. All adjustments should be
made with the carburetor in the operating position.
Turn both the main and idle mixture adjusting screws in
(clockwise) until finger tight.
Now back the mixture screws out (counterclockwise) to
Engine Model
All models with float-type
carburetors
All models with diaphragm-type
carburetors
Carburetor Model Number
LMH
WHG & LME
LMK
Tecumseh Carburetors
Main Pre-set
1-1/2 turn 1 turn
1 turn 1 turn
Walbro Carburetors
1-1/2 turn
1-1/4 turn
Fixed
Idle Pre-set
1-1/2 turn
1-1/4 turn
1 turn
obtain the pre-set figure in the chart shown at right.
FINAL ADJUSTMENTS (NON EMISSION ENGINES)
Start the engine and allow it to warm up to normal operating temperature (3 - 5 minutes). Set the speed control to the
HIGH or FAST position. From the recommended preset position, turn the main mixture adjustment screw in (clockwise)
slowly until the engine begins to run erratic (lean). Note the position of the screw. Now , turn the screw out (counterclockwise)
until the engine begins to run erratic (rich). Turn the screw in (clockwise) midway between these two positions. This will
be the best setting. (diag. 24, 25 & 26).
Set the speed control to the IDLE or SLOW position. Adjust the idle mixture screw following the same procedure used to
adjust the main mixture adjustment screw.
TECUMSEH CARBURETORS
DIAPHRAGM
26
IDLE MIXTURE
SCREW
SERIES 1
MAIN MIXTURE
SCREW
24
IDLE MIXTURE
SCREW
SERIES 3 & 4
MAIN MIXTURE
SCREW
IDLE MIXTURE
25
SCREW
MAIN MIXTURE
SCREW
If further adjustment is required, the main adjustment should be made under a loaded condition.
If the engine stops or hesitates while engaging the load (lean), turn the main mixture adjusting screw out (counterclockwise)
1/8 turn at a time, testing each setting with the equipment under load, until this condition is corrected.
If the engine smokes excessively (rich), turn the main adjusting screw in (clockwise) 1/8 turn at a time, testing each
setting with the equipment under load, until this condition is corrected.
After the main mixture screw is set, move the speed control to the IDLE or SLOW position. If the engine does not idle
smoothly , turn the idle mixture screw 1/8 turn either in (clockwise) or out (counterclockwise) until engine idles smoothly .
Recheck the high and low R.P.M. setting and adjust as necessary.
NON-ADJUSTABLE CARBURETORS
DUAL SYSTEM AND SERIES 6
SERIES 8, 11 & BRIDGED 11
MIXING WELL
CAST BUT
NOT
MACHINED
SERIES 9
SERIES 10
CHOKE
NON-ADJUSTABLE
PRIMER NO CHOKE
16
CAPPED FIXED JET
27
28
CAST BUT NOT MACHINED
IDLE JET
29
CAPPED IDLE
RESTRICTOR
30
DISASSEMBLY PROCEDURE
NOTE: Engines which are identified as compliant with CARB (California Air Resources Board) or EPA (US
Environmental Protection Agency) regulations can NOT be changed from the factory settings unless specifically
authorized.
FLOAT STYLE CARBURETORS
1. Note or mark the high and low mixture adjusting screws
to aid in reassembly (if applicable). Remove the high
speed adjusting screw, bowl nut, and float bowl.
Remove the idle mixture screw assembly .
2. Note the position of the spring clip on the inlet needle
and float, the long end of the clip must face toward the
choke end of the carburetor. Remove the float hinge
pin with a needlenose pliers. Some carburetors use a
float dampening spring to aid the inlet valve in
maintaining a steady position during rough service
applications. Note the position of the hooks before
removing the float hinge pin (diag. 31).
3. Remove the float, clip, and inlet needle.
LONG END OF CLIP
TOWARD CHOKE
CHOKE
END
CLIP
OPEN END OF CLIP
THROTTLE
END
31
4. Remove the inlet needle seat using the Tecumseh
carburetor tool #670377 as shown. Push the hook
through the hole in the center of the seat to remove it.
(diag. 32).
5. Note or mark the action of the choke and throttle
shutters, and/or the hook points of the choke or throttle
return spring, or seal retainer springs located on the
top of the choke and/or throttle shaft. Remove the
throttle shutter, throttle shaft, choke shutter, springs
and choke shaft by removing the screw(s) that attach
the throttle or choke shutter to the shaft inside the air
horn.
6. Remove the primer bulb (if equipped) by grasping it
with a pliers and pulling and twisting out of the body .
Remove the retainer by prying and lifting it out with a
screwdriver. Do not re-use the old bulb or retainer (diag.
33).
7. Some T ecumseh float style carburetors have a damper
spring which is installed as shown. (diag. 34)
Use carb. tool
# 670377
32
33
34
17
8. Remove all welch plugs if cleaning the carburetor.
Secure the carburetor in a vise equipped with protective
jaws. Use a small chisel sharpened to a 1/8"
(3.175 mm) wide wedge point. Drive the chisel into the
plug to pierce the metal, then push down on the chisel
to pry the plug out of the hole (diag. 35).
NOTE: DO NOT REMOVE ANY BALL OR CUP PLUGS
(diag. 37).
SMALL CHISEL
PRY OUT
PLUG
DO NOT ALLOW
CHISEL POINT
TO STRIKE
CARBURETOR
BODY OR
CHANNEL
REDUCER
PIERCE PLUG WITH TIP
WELCH PLUG TO BE
SMALL CHISEL
REMOVED
ABOUT 1/8"
(3.175 mm)
WIDE
35
9. Note the direction of the inlet fitting. If necessary the
inlet fitting can be removed. (See page 24).
10. The main nozzle on Series 8 and Series 9 carburetors
can be removed by pressing the tube outward from the
venturi thru the center leg. This nozzle is non-metallic
and has an "O" ring seal on the top and bottom end of
the tube. Do not remove a main nozzle that is made of
brass from any Tecumseh carburetor. These are
pressed in at the factory to a specific depth. When
removing the nozzle, the top "O" ring may not come
out with the tube. The "O" ring must be removed and
placed on the nozzle before it is placed back into the
center leg or it will not seal properly . (diag. 38)
11. Servicing the standard series eleven and bridged
model.
When servicing the series eleven DO NOT soak it in
dipping type carburetor cleaners, use only spray
cleaner or standard solvent tank cleaners. Proper
cleaning requires removal of both welch plugs and
cleaning of the restictor(s) as equipped.
The standard series eleven has one restictor in the
extended prime well as shown (diag. 36). The Bridged
series eleven has an additional restrictor on the idle
leg of the carburetor as shown (diag. 37). Both are
cleaned using spray carburetor cleaner, compressed
air and soft tag wire no larger than .012 inch (.3mm) or
damage will occur.
WELCH PLUG
FUEL INLET
DO NOT REMOVE PLUGS
BRASS OR BALL PLUG
BALL PLUG
OR RESTRICTOR HOLE
IF BRIDGED SERIES 11
EXTENTED PRIME
FUEL PASSAGE
(SUPPLIES FUEL
AFTER ENGINE START)
EXTENDED
PRIME FUEL
CHAMBER
RESTRICTOR
WELCH PLUG
MAIN JET
IDLE FUEL PASSAGE
REDUCTION ROD INSIDE
NOT MACHINED ON SERIES 11
36
37
NOT USED ON SERIES 7
OR VECTOR CARBS.
"O" RING
ON TOP OF STEP
(IN GROOVE)
The main nozzle on some Walbro carburetors are
removable for service. If you remove it, a service nozzle
with the under cut fuel passage must be installed or
problems will occur (diag. 39).
18
"O" RING IN GROOVE
"O" RING
SERVICE MAIN NOZZLE
REUSABLE
UNDERCUT
ANNULAR
GROVE
ORIGINAL MAIN NOZZLE
DO NOT REUSE
38
39
Diaphragm Carburetors
1. Remove the screws holding the diaphragm cover on.
2. Remove the cover , gaskets, and diaphragm noting or
marking the sequence or location to aid in reassembly.
NOTE: If a "F" designation on the choke end of the
carburetor is present, place the diaphragm on first, then
the gasket and cover. If no "F" is present, the gasket
goes first.
3. Note or mark the high and low mixture adjustment
screws. Remove the screw assemblies.
4. Note or mark the action of the choke and throttle
shutters and the hook points of the choke or throttle
return spring or seal retainer springs located on the top
of the choke or throttle shaft. Remove the throttle
shutter, throttle shaft, choke shutter , springs and choke
shaft by removing the screw or screws that attach the
throttle or choke shutter to the shaft inside the air horn.
5. Use a 9/32" (7.144 mm) thin wall socket to unscrew
and remove the inlet needle and seat assembly (diag.
40).
6. Note and mark the direction of the inlet fitting. If
necessary the inlet fitting can be removed by pulling
with a pliers or vise. Some diaphragm carburetors have
a strainer as an integral part of the fuel fitting. If the
strainer is lacquered or cannot be cleaned, the fitting
must be replaced.
7. Remove all welch plugs if cleaning the carburetor.
Secure the carburetor in a vise equipped with protective
jaws. Use a small chisel sharpened to a
1/8" (3.175 mm) wide wedge point. Drive the chisel
into the plug to pierce the metal, then push down on
the chisel to pry the plug out of the hole.
NOTE: DO NOT REMOVE ANY BALL OR CUP PLUGS.
CRANKCASE PRESSURE
ê
ATMOSPHERIC PRESSURE ACTING ON
á
DAMPING DIAPHRAGM
FUEL FLOW
á
"F"
DIAPHRAGM FIRST NOT GASKET
VALVE CLOSED
ATMOSPHERIC
VENT
VALVE OPEN
FUEL SUPPLY
CRANKCASE SUCTION AND
ê
FLOW DIRECTION
ATMOSPHERIC PRESSURE
ACTING ON DAMPING
á
DIAPHRAGM
"F" DESIGNATION
CARBURETOR
FITTING
VALVE OPEN
DIAPHRAGM
FILTER
AIR BLEED
VALV E
CLOSED
PULSE LINE
TO CRANKCASE
SUCTION FUEL FLOW DIRECTION
á
ATMOSPHERIC PRESSURE CAUSED
FUEL FLOW
ê
40
41
IMPULSE FUEL PUMP
T o service, disassemble the pump by removing the four (4)
screws. Clean all parts with a solvent and install a new kit
which consists of a coil spring, gaskets and diaphragms
(diag. 41 & 42).
FLOAT ADJUSTING PROCEDURE
All T ecumseh carburetors with an adjustable float require
a specific float height adjustment to achieve proper
operation and easy engine starts. T o check the float height,
hold the carburetor in an upside down position. Remove
the bowl nut, float bowl, and "O" ring. Place the T ecumseh
carburetor tool #670377 with flat dimensions of 1 1/64" (4.36
mm) across the top of the carburetor casting on the opposite
side and parallel to the float hinge pin (diag. 43). The float
must just touch the carb tool. If the float is too high or too
low, adjust the height by bending the float tab accordingly .
If the required adjustment is minor, the tab adjustments
may be made without removing the float and carefully
inserting a small bladed screwdriver to bend the tab.
Float sticking can occur due to fuel deposits or when the
fuel tank is filled for the first time, this condition can be
quickly corrected by loosening the carburetor bowl nut one
full turn. Turn the bowl 1/4 turn in either direction, then
return the bowl to its original position and tighten the bowl
nut.
OLD STYLE
Carb. tool # 670377
NEW STYLE
RIM
42
43
19
INSPECTION
After careful disassembly of the carburetor and the removal of all non metallic parts, the carburetor body and all other
metallic parts should be cleaned with solvent, or commercial carburetor cleaner, no longer than 30 minutes. Use compressed
air and soft tag wire to clean internal carburetor passages. T o do a proper cleaning job, the welch plugs must be removed
to expose the drilled passages.
NOTE: The nylon check balls used in some diaphragm carburetors are not serviceable. Nylon can be damaged if subjected
to harsh cleaners for prolonged periods.
Throttle and Choke
Examine the throttle lever and shaft, choke lever and shaft, and carburetor body at the bearing points and holes into which
the linkage is fastened, and replace if worn or damaged. Any looseness in these areas can cause dirt to enter the engine
and cause premature wear. If dust seals are present, these should be positioned next to the carburetor body .
Idle and High Speed Mixture Adjusting Screw
RETAINER NUT
Examine the idle mixture needle tip and tapered surface
for damage. The tip and tapered surface of the needle must
not show any wear or damage at all. If either is worn or
damaged, replace the adjusting needle. Tension is
maintained on the screw with a coil spring. Examine and
replace the “O” ring seal if damaged (diag. 44).
Examine the tapered surface of the high speed mixture
needle. If the tapered surface is damaged or shows wear,
replace the needle (non-emissioned). Some Tecumseh
carburetors use serviceable jet main nozzles. These are
identified as being non-metallic.
FUEL-
Fuel Bowl Retaining Nut
METERING
PORT
ONE-HOLE TYPE
The retaining nut contains the transfer passage or metering
jet through which fuel is delivered to the high speed and
idle circuit of the carburetor. If a problem occurs with the
idle circuit, examine the small fuel passage in the annular groove in the retaining (metering) nut. This passage must be
clean for the proper transfer of fuel into the idle metering circuit. Torque retaining nut to 50 in. lbs. (5.65 Nm) when
reinstalling.
"O" RING
BRASS WASHER (used to protect the
"O" ring from the spring)
SPRING
HIGH SPEED
ADJUSTMENT SCREW
IDLE FUEL
TRANSFER
PASSAGE
TW0-HOLE TYPE
FUEL-INLET
PORTS
44
45
There are two different types of bowl nuts that are used on adjustable main, float style carburetors. One type has one fuel
metering port at the bottom of the nut, and the other has two fuel inlet ports at the bottom of the nut. This difference
relates to calibration changes to the carburetor and is dependent on the application (diag. 45).
NOTE: DO NOT INTERCHANGE BOWL NUTS.
The fuel inlet ports must be free of any debris to allow proper fuel flow.
Fuel Bowl, Float, Needle and Seat
The float bowl must be free of dirt and corrosion. Clean with solvent or carburetor cleaner.
Examine the float for damage. Check the float hinge bearing surfaces for wear, as well as the tab that contacts the inlet
needle. Replace any damaged or worn parts.
The needle and seat should be replaced if any fuel delivery problems are experienced (flooding or starvation). Sealing
problems with the inlet needle seat may not be visible, so replacement is recommended.
Diaphragms, Pulse Pumps, and Primer Bulbs
Inspect diaphragms, gaskets, and primer bulbs for cracks, tears, hardness or brittleness. Replace if necessary .
20
ASSEMBLY
Welch Plugs
To install a new welch plug after cleaning the carburetor,
secure the carburetor in a vise equipped with protective
jaws. Place the welch plug into the receptacle with the
raised portion up. With a punch equal to, or greater than
the size of the plug, merely flatten the plug. Do not dent or
drive the center of the plug below the top surface of the
carburetor. After installation of the welch plug, seal the
outer diameter with finger nail polish or equivalent (diag.
46).
Throttle Shaft and Plate
When reassembling, it is important that the lines or lettering
on the throttle plate are facing out when in the closed
position. Position throttle plate with two lines at 12 and 3
o’clock. If the throttle plate has only one line, the line should
be positioned in the 12 o’clock position on Series 1, 6, 8,
and 9 carburetors, and positioned in the 3 o’clock position
on Series 3 and 4 carburetors (diag. 47 & 48).
Test the operation of the throttle and return spring (if
equipped). If binding occurs, correct by loosening screws
and repositioning throttle plate.
NEW WELCH PLUG
THROTTLE
PLATE
FLAT END PUNCH
SAME OR LARGER
DIAMETER OF
PLUG
46
SERIES 1, 6, 8, 9, 10
THROTTLE LEVER
TWELVE O'CLOCK
POSITION
47
SERIES 3 AND 4
THREE O'CLOCK
POSITION
Always use a new screw(s) when reinstalling the throttle
shutter (Tecumseh screws are treated with dry-type
adhesive to secure them in place).
NOTE: NEVER REUSE OLD SCREWS.
Choke Shaft and Plate
The choke plate is inserted into the air horn of the carburetor
in such a position that the flat surface of the choke is down.
Choke plates will operate in either direction. Make sure it
is assembled properly for the engine. T est the operation of
the choke and return spring function if equipped (diag. 49).
Always use a new screw(s) when reinstalling the choke
shutter as the screws are treated with dry-type adhesive
to secure them in place.
NOTE: NEVER REUSE OLD SCREWS.
The choke shaft and plate must be in the closed position
prior to tightening the screws. Hard starting may be due to
insufficient choking action because of a misaligned choke
plate. Correct by readjusting the choke plate to close
completely. Note the cut-out position of choke shutter if
applicable.
CHOKE PLATE
FLAT
DOWN
48
49
CHOKE PLATE
Fuel Inlet Fitting
Support the carburetor body with a wood block to avoid
damage to other parts. Use a bench vise or press to install
the fitting squarely . Insert the tip into the carburetor body ,
coat the exposed portion of the shank with Loctite grade
A, then press it in until the shoulder contacts the carburetor
body .
FLAT SIDE DOWN
50
21
High and Low Speed Adjusting Screw, Main Nozzle
When reassembling, position the coil spring on the adjusting
screws, followed by the small brass washer and the “O”
ring seal. Turn the high speed adjustment screw in
approximately one turn into the bowl retainer nut to make
an assembly (diag. 51).
On 2-7 hp. engines that use carburetors which have the
metering rod in the idle circuit (carburetor should rattle when
shaking), make certain that the idle adjustment screw is
installed when the carburetor is in an upright position or
the needle will damage the metering rod, adjustment screw
and carburetor casting.
Some carburetors are of the fixed main type and would not
have a high speed adjusting screw.
Inlet Needle and Seat
On float type carburetors, make sure the seat cavity is
clean. Moisten the seat with oil and insert the seat with
the grooved side down and away from the inlet needle.
Press the seat into the cavity using the Tecumseh
carburetor tool #670377 making sure it is firmly seated
(diag. 52).
The inlet needle hooks onto the float tab by means of a
spring clip. T o prevent binding, the long, straight end of the
clip should face the air intake end of the carburetor as
shown (diag. 53).
On diaphragm carburetors the inlet needle and seat
assembly are installed by using a socket to tighten the
assembly until seated.
Needle and Seat Pop-Off Test
To test the pop-off pressure, remove the carburetor from
the engine. Be sure to drain any fuel into an approved
container. Invert the carburetor and remove the float bowl.
This test is best performed when the carburetor is placed
upside down and level in a soft jawed vice. Lift the float
and needle assembly off of the seat in order to place a
drop of WD-40 on the tip of the needle or on the seat surface.
Reposition the float and needle assembly. Using the
Tecumseh Leak Tester part # 670340, connect the high
pressure regulator to the low pressure regulator and attach
the clear low pressure air line to the carburetor fuel inlet.
Apply approximately 5-6 psi of compressed air, close the
gate valve and disconnect the low pressure guage from the
high pressure guage. Monitor the low pressure guage to
make sure the needle shouldn't drop below 1.5 psi before
1 minute of time elapses. If the minimum of 1.5 psi cannot
be maintained for this period of time, then replacement of
the needle and seat is required.
Float Installation
RETAINER NUT
TORQUE NUT TO
50 IN. LBS. (5.65 Nm)
PRESS IN UNTIL
SEAT RESTS ON
BODY SHOULDER
INLET NEEDLE MAKES
CONTACT HERE
LONG END
OF CLIP
CHOKE
END
FLOAT
"O" RING
BRASS WASHER
SPRING
HIGH SPEED
ADJUSTMENT SCREW
51
CARB TOOL #670377
SEAT
INSERT THIS
FACE FIRST
52
CLIP
OPEN END
OF CLIP
THROTTLE
END
53
INLET NEEDLE
FLOAT SPRING
HINGE PIN
54
Reinstall the inlet needle and float into the carburetor. The long end of the spring or clip on the inlet needle must point
toward the air intake end of the carburetor. If a float dampening spring is used, reassemble using the following steps (diag.
54).
1. Place the float upside down.
2. Position the spring on the float with the long end around and to the back side of the float’s center back tang. The ends
must point toward the choke end of the carburetor. Hook the inlet needle clip on the inside float tang so the clip end
points to the choke end of the carburetor (diag. 54).
3. Place the float, float spring, clip and inlet needle in position between the hinge legs of the carburetor. As the float
assembly nears the hinge legs, wind the outside end of the spring so it goes to the outside of the leg (counterclockwise
looking from the choke end).
22
4. Install the hinge pin from the opposite hinge leg. The
bowl gasket must be positioned over the end of the
spring (diag. 55).
5. Set the proper float height. See “Float Adjusting
Procedure” in this chapter.
GASKET GOES
OVER SPRING
Diaphragm Assembly
The rivet head on the diaphragm must always face toward
the inlet needle valve. On carburetors with an “F” cast into
the carburetor flange as illustrated, the diaphragm goes
next to the carburetor body . Other diaphragm carburetors
have the gasket located between the diaphragm and
carburetor body. Install the cover retaining screws and
tighten (diag. 56).
Fuel Bowl And Bowl Nut
Whenever a carburetor bowl is removed for service, the
fuel bowl “O” ring must be replaced. For easier installation,
lubricate the “O” ring with a small amount oil.
Install the float bowl by placing the detent portion opposite
of the hinge pin. Make sure the deepest end of the bowl is
opposite of the inlet needle. The bowl has a small dimple
located in the deepest part. The purpose of this dimple is
to minimize the chances of the float sticking to the bottom
of the bowl caused by stale fuel (diag. 57).
On some fixed jet (non-adjustable) and adjustable
carburetors, a fibered washer is required between the
carburetor bowl and the bowl retaining nut.
RIDGE AND
RIVET
HEAD UP
DETENT
GASKET
CHOKE END OF
CARBURETOR
ENDS OF SPRING POINT
TOWARD CHOKE END
OF CARBURETOR
55
RIDGE AND
RIVET HEAD
UP
GASKET
56
Occasionally, on engines equipped with the dual system
carburetor, some rich starting conditions have occurred
when the engine is warm. This condition can be corrected
by inserting a non-metallic spacer in the center leg of the
carburetor, as shown (part # 632158). This spacer is
designed to reduce the amount of prime charge in the main
nozzle area for better starting under warm engine
conditions. It can only be used on Dual System carburetors
and does not lean out the carburetor mixture. (diag. 58)
This spacer must be reinstalled if originally equipped in
the carburetor.
Impulse Fuel Pump
The diaphragms must be installed against the center body
with the gaskets against the outside covers. The parts are
designed so they cannot be misassembled without damage
(diag. 58).
To test the unit, assemble the carburetor to the engine,
leaving the fuel line from the pump off. Use a different fuel
tank remotely placed above the carburetor to provide gravity
fuel flow to the carburetor inlet to run the engine while testing
the pump. Make sure fuel is available in both fuel tanks
and that the original fuel tank's fuel line is connected to the
fuel pump inlet. Place the pump outlet line in a proper
draining receptacle. With the pulse line connected from
the engine crankcase to the pump and the engine running,
a definite fuel flow should result at the pump outlet.
57
NON-METALLIC
SPACER
58
If the flow is erratic or intermittent, the pump needs repair
or replacement.
23
Primer Bulb
To install, start the retainer and bulb into the casting with
the retainer tabs pointed out. Firmly push the bulb and
retainer into position using a 3/4'’ (19.05 mm) deep well
socket (diag. 59).
Final Checks
Before reinstalling a newly overhauled carburetor, pre-set
the main mixture adjustment screw, the idle mixture
adjustment screw and the idle speed adjustment screw.
See “Pre-sets and Adjustments” in this chapter.
59
STANDARD SERVICE CARBURETORS
T ecumseh supplies some replacement carburetors on which parts from the old carburetors can be reused or new parts
added. This Standard Service Carburetor helps to reduce dealer inventories.
Standard Service Carburetors are built in both float and diaphragm versions.
The parts from the original carburetor that are necessary to make a standard service carburetor are: choke shaft, shutter
and spring, throttle lever and spring, fuel fitting, idle adjustment screw and spring. If any or all of these old parts are worn
or damaged, replace each part with a new service part to assure proper function and prevent engine damage. Use the
diagrams on the next page as a guide to facilitate the correct installation of parts (diag. 61 & 62).
Fuel Fitting
NOTE: MOST SERVICE CARBURETORS ARE MARKED “SVC CARB NF” IN THE PRICE LIST. THIS MEANS THAT
THE CARBURETOR COMES WITH NO FUEL FITTING.
Use the parts manual to obtain the same fuel inlet fitting that was installed in the original carburetor. Install the fuel fitting
in the new carburetor body in the same position as on the original carburetor. Support the carburetor body with a wood
block to avoid damage to other parts. Use a bench vise or press to install the fitting squarely . Press it in until it bottoms
out.
NOTE: PRESS FUEL FITTING IN SQUARELY USING CAUTION SO THA T THE CARBURETOR BODY IS NOT DAMAGED.
Inlet Fuel Fitting
To remove a leaking or damaged fuel inlet fitting, use a
1/4"(6 mm) bolt, 1/4" (6 mm) nut and 1/4" (6 mm) washer,
along with a 1/2" (12 mm) nut. Use a pliers or vise to
remove the plastic part of the inlet fitting. Tap the inside
of the remaining metal portion of the fitting using a
1/4"- 20 (6 mm) tap. Place a 1/2" (12 mm) nut over the
fuel fitting (it may be necessary to guide one side of the
nut to seat it squarely to the carburetor). Next thread the
1/4" (6 mm) nut on the bolt until it contacts the shank,
add the washer, and thread the bolt into the fitting until
snug. Tighten the 1/4"- 20 (6 mm) nut until the fitting is
removed. (diag. 60)
60
Choke Shaft
NOTE: Never reuse choke or throttle shutter screws, always replace with new T ecumseh service screws.
Remove the choke shutter screw from the original carburetor and remove the choke shaft. Observe the position of the
ends of the choke return spring if one is present. Also observe the position of the cut-out and/or holes in choke shutter.
Some chokes turn clockwise and some turn counterclockwise, note the position of the choke shaft prior to removal from
the old carburetor.
If a choke stop spring is present on the new carburetor and is not used on the old carburetor, cut it of f with a side cutter
or pull it out using a pliers.
T est the action of choke shaft to make sure it moves freely and easily and does not bind in either open or closed position.
If binding occurs, loosen the shutter screw; reposition the shutter and tighten the screw.
24
Throttle Lever
Remove the throttle lever and spring and file off the peened end of the throttle shaft until the lever can be removed. Install
the throttle spring and lever on the new carburetor with the self-tapping screw furnished. If dust seals are furnished, install
them under the return spring.
Idle Speed Adjustment Screw
Remove the screw assembly from the original carburetor and install it in the new carburetor. T urn it in until it contacts the
throttle lever. Then an additional 1-1/2 turns for a static setting.
Final Checks
Consult the service section under “Pre-sets and Adjustments” and follow the adjustment procedures before placing the
carburetor on the engine.
FLOAT TYPE CARBURETOR DIAPHRAGM TYPE CARBURETOR
CHOKE SHAFT
SELF TAPPING SCREW
THROTTLE LEVER
AND SHAFT
IDLE CRACK
SCREW AND
SPRING
WASHER
FELT SEAL
CHOKE STOP
SPRING
SHUTTER
SCREW
FLOAT
SPRING
LEVER
SPRING
WASHER
FELT SEAL
THROTTLE SHAFT
SHANK
FUEL FITTING
"O" RING
SEAT AND CLIP
INLET NEEDLE
SPRING CLIP
FLOAT SHAFT
FELT SEAL
THROTTLE SHUTTER
SHUTTER SCREW
IDLE
ADJUSTMENT
SCREW
SEAL
WASHER
SPRING
LOW SPEED
ADJUSTMENT
SCREW
SPRING
WASHER
HIGH SPEED
ADJUSTMENT
SCREW
CHOKE LEVER
AND SHAFT
FUEL INLET
CHOKE
SHUTTER
SHUTTER
SCREW
DIAPHRAGM
DIAPHRAGM
GASKET
DIAPHRAGM
COVER
FLOAT BOWL
BOWL NUT WASHER
HIGH SPEED BOWL NUT
61
PRIMER FITTING
DIAPHRAGM
COVER SCREW
62
25
CHAPTER 4 GOVERNORS AND LINKAGE
GENERAL INFORMA TION
This chapter includes governor assembly and linkage illustrations to aid in governor or speed control assembly .
Tecumseh 4 cycle engines are equipped with mechanical type governors. The governor ’s function is to maintain a
constant R.P.M. setting when engine loads are added or taken away. Mechanical type governors are driven off the
engine’s camshaft gear . Changes in engine R.P .M. cause the governor to move the solid link that is connected from the
governor lever to the throttle in the carburetor. The throttle is opened when the engine R.P.M. drops and closes as the
engine load is removed.
OPERATION
As the speed of the engine increases, the governor weights
(on the governor gear) move outward by centrifugal force.
The shape of the governor weights force the governor spool
to lift. The governor rod maintains contact with the governor
spool due to the governor spring tension. As the spool
rises, the governor rod rotates, causing the attached outer
governor lever to pull the solid link and close the throttle
opening. When the engine speed decreases, the lower
centrifugal force allows the governor weights to be pulled
in by the governor spring. As the spool lowers, the governor
rod rotates and the solid link pushes the throttle to a more
open position (diag. 1).
INTERNAL COMPONENTS (VARIOUS STYLES)
RETAINING
RING
SPOOL
RETAINING
RING
GEAR ASSY.
(GOV.)
WASHER
SHAFT
SPOOL
UPSET
NO RETAINING
RING
SHAFT
GEAR ASSY.
(GOV.)
WASHER
RETAINING
RING
WASHER
RETAINING
WASHER
SHAFT
THROTTLE
SPOOL
RING
GEAR ASSY.
(GOV.)
SPACER
GOVERNOR SHAFT
WEIGHTS
GOVERNOR GEAR
SHAFT
ROD
ASSY
(GOV.)
WASHER
BRACKET
RETAINING
SPRING
SPOOL
RING
GEAR
ASSY.
(GOV)
GOVERNOR
SPOOL
SPOOL
SHAFT
GEAR ASSY.
(GOV.)
WASHER
1
SCREWS
TVS STANDARD
2
TVS UPSET HORIZONTAL LEV
3
MEDIUM FRAME
4
5
6
TROUBLESHOOTING
Engine problems where the governor is suspected to be the cause, may actually be the result of other engine system
problems. Hunting (engine R.P .M. surging up and down) indicates that the engine is incapable of maintaining a constant
R.P .M. with or without an engine load. Engine overspeeding (either with or without throttle movement) must be corrected
immediately before serious engine damage occurs. Use the following procedure to diagnose a suspected governor
problems.
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