Tecumseh Carburetor Manual

Tecumseh Carburetor Manual
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Tecumseh Power

Service Dealer’s and Technician’s Training and Informational Series

Carburetor Identification, Troubleshooting and Service

TecumsehPower

ENGINES & TRANSMISSIONS

Table of Contents

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Engine Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Fuel Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 High Altitude Jet for Emissionized Carburetors . . . . . . . . . . . . . . . . 3 High Altitude Carburetor Kits for Fixed Main Carburetors. . . . . . . . . . . 4 Throttle Control Brackets, Governors, and RPM Adjustments . . . . . . . . 5 How to Identify a TecumsehPower Carburetor . . . . . . . . . . . . . 5 - 10 Non-TecumsehPower Carburetors . . . . . . . . . . . . . . . . . . . . . 10 Diaphragm Carburetors . . . . . . . . . . . . . . . . . . . . . . . . . 10 - 11 Carburetor Cleaning Series 8 - 11 . . . . . . . . . . . . . . . . . . . 12 - 16 Emission Carburetors . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Pre-Sets and Adjustments (Non-Emission) . . . . . . . . . . . . . . . 18 - 20 Troubleshooting Carburetion Chart . . . . . . . . . . . . . . . . . . . 21 - 22 Troubleshooting TecumsehPower Carburetors . . . . . . . . . . . . . . . .. 23. Troubleshooting Carburetion TC Series Chart . . . . . . . . . . . . . 24 - 25 Troubleshooting Walbro and Tillotson . . . . . . . . . . . . . . . . . . . . 26 Metering System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 Service Carburetor Information . . . . . . . . . . . . . . . . . . . . . 27 - 28 Using the Computer Parts Look Up System. . . . . . . . . . . . . . . . . 29 Float Adjustment Procedure . . . . . . . . . . . . . . . . . . . . . . . . . 29 Carburetor Service Tips . . . . . . . . . . . . . . . . . . . . . . . . . 30 - 33 Primer Bulb Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 Fuel Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 Internal Atmospheric Vent Passage . . . . . . . . . . . . . . . . . . . . . 35 Failure Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 - 38

I

INTRODUCTION

This troubleshooting book is designed as a quick reference for carburetion problems and an aid in identifying failures and their possible causes. It also directs the user to other publications and printed material that assist in properly resolving problems or making adjustments not related to carburetion but could affect carburetion.

Listed below are some basic DO’S and DON’TS to be followed when making carburetor repairs.

PLEASE DO:

Follow all instructions carefully.

Use new service replacement screws (650506 Torx 8) for the choke and throttle shutters (screws are treated with a dry-type adhesive to secure them in place).

Use TecumsehPower float tool 670377 or an 11/64 drill bit to set the proper float height. Remove the bowl gasket and measure from the casting surface. The gasket should be replaced or poor starting may result.

Use only genuine TecumsehPower service parts.

Remove all welch plugs, o-rings and non-metallic main nozzles before cleaning carburetor in cleaner.

DO NOT:

Use drill bits to clean passages.

Enlarge passages.

Soak carburetor in a cleaner over 30 minutes.

Reuse original choke and throttle shutter screws.

Interchange bowl nuts.

Reuse gaskets and “O” rings.

ENGINE TROUBLESHOOTING

When troubleshooting a carburetor, other areas such as valves, fuel tank venting or gaskets should not be overlooked. The carburetor is dependent on the proper operation of the engine to do its job. The first step in troubleshooting is to determine if you have a carburetor or an engine problem.

In order for the engine to operate properly, the following items need to be checked first:

1.Make sure there is a sufficient amount of clean, fresh fuel in the tank.

2.Check spark plug for proper reach, gap and condition. Replace, if needed, or in question. Perform an ignition test using spark tester part number 670366 to assure that you have a crisp spark.

NOTE

On older point ignitions models check for proper ignition timing according to the Technician's handbook.

3.Check for fuel flow restrictions into the carburetor. Deteriorated fuel line, and fuel cap venting are some of the more common restrictions. TecumsehPower uses a stainless steel 75 micron filter screen molded into most tanks. It is extremely rare for this area to become restricted and should be checked last.

4.Check compression by first disconnecting the spark plug lead and ground it to prevent start-up. Next, turn the engine over by hand. A definite resistance should be noticed on the compression stroke. Using a cylinder leak down tester is also possible.

After these basic checks have been performed and you are satisfied with the engine's condition, attempt to start it. If it does not start, remove the spark plug and check its condition. If it is dry, you can assume there is a problem with the carburetor or the fuel system. Continue by troubleshooting the carburetor.

1

FUEL RECOMMENDATIONS

FUEL

TecumsehPower 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 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.

STORAGE

IF THE ENGINE IS TO BE UNUSED FOR 30 DAYS OR MORE

WARNING Gasoline (Fuel) vapors are highly flammable and can explode. Fuel vapors can spread and be ignited by a spark or flame many feet away from the engine. To prevent injury or death from fuel

fires, follow these instructions:

Never store the engine with fuel in the fuel tank inside a building with potential sources of ignition such as hot water and space heaters, clothes dryer, electric motors, etc.

Gasoline can become unstable 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 such as TecumsehPower Ultra-Fresh part number 730245 to the gasoline. Fuel stabilizer should be 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.

Draining the Fuel System

WARNING Do not attempt to pour fuel from engine or siphon fuel by mouth. Empty fuel tank by using a commercially available suction device designed for use with gasoline. Then run the engine until

any remaining fuel is consumed. Doing so may result in death or serious injury.

CAUTION Drain the fuel into an approved container outdoors, and away from any open flame or combustion source. Be sure the engine is cool.

NOTE

If gasohol has been used, put a small amount of unleaded gasoline into fuel tank and repeat preceding instructions, then run engine until fuel is used up.

Oil Cylinder Bore

1.Remove the spark plug wire from the spark plug. NOTE: Always ground the plug wire when disconnected. Pull the starter handle slowly until resistance is felt from compression pressure, then stop. Slowly release starter tension to prevent the engine from reversing due to compression pressure.

2.Remove the spark plug, squirt 1/2 ounce (15 ml.) of clean engine oil into the spark plug hole.

3.Cover the spark plug hole with a shop towel and crank the engine over slowly, several times.

4.Replace the spark plug and tighten. Pull the starter handle as performed in step #1. The piston position blocks the cylinder ports on 2 cycle engines or closes the valves on 4 cycle engines, preventing air from entering and oil from leaving the cylinder bore during storage.

5.Re-connect the spark plug wire on the spark plug.

2

HIGH ALTITUDE JET

FOR EMISSIONIZED CARBURETORS

The following list of altitude compensation jets is being provided for use with emission grade carburetors at elevations between 6,000 and 11,000 feet (1,824 - 3,344 meters).

This list applies only to engines which are identified as compliant with CARB (California Air Resource Board) or EPA US Environmental Protection Agency) regulations.

To determine the proper jet for your carburetor, simply locate the number stamped into the original bowl nut. Then use the chart below to identify and install the proper jet.

NOTE: Installation of altitude compensation jets is NOT WARRANTY

STANDARD JET

SERVICE

NUMBER

NUMBER

148

640181

152

640011

157

640032

158

640008

162

640024

166

640015

176

640059

181

640106

183

640114

184

640128

188

640170

190

640163

191

640162

202

640184

205

640208

206

640209

207

640210

USE

HIGH ALT. JET

SERVICE

BETWEEN 6,000 TO 11,000 FT

NUMBER

(1,824 TO 3,455 M)

 

203

640206

183

640114

169

640087

175

640062

149

640185

158

640008

170

640089

167

640188

184

640128

206

640209

163

640187

152

640011

158

640008

205

640186

203

640206

148

640181

206

640209

3

HIGH ALTITUDE CARBURETOR KITS

FOR FIXED MAIN CARBURETORS

NOTE

This list applies only to products built prior to emissions regulation. Engines which are identified as compliant with CARB (California Air Resources Board) or EPA (US Environmental Protection Agency) regulations can NOT be changed from their factory setting unless specifically authorized.

Engines built to O.E.M. specifications may experience starting and operating problems when used in areas where the altitude is 4,000 feet (1220 meters) above sea level or higher.A leaner fuel/air mixture is desirable at higher elevations to sustain good engine startability and operating characteristics. Engines built with adjustable idle and main circuit carburetors can be adjusted to optimize performance.

The following will assist you in selecting the correct high altitude/leaner jetted bowl nut for engines equipped with fixed main or dual system carburetors. Order parts from your Authorized TecumsehPower Distributor or Dealer.

4 CYCLE

STANDARD BOWL/NUT

 

 

 

ENGINE

STAMPED

Over 4,000 Ft.

TVS90-120/ECV90,100/TNT100

64, 65, 75, 79, 103,-

 

 

108, 126, 127, 137

632455

TVS90-120 / OHH50 / 55

158, 161, 164, 165, 166, 171, 172, 177

632737

TVS90 -120, OVRM40-60

124, 125,133, 135, 136

631026

OVM & OVXL120, OHV11-13 (Formula)

120, 141

632239

Dellorto

69

633017

VLV40, 50, 55, 60

Jet

632648

VLV40, 50, 55, 60

Nozzle

632638

TVM170-195

83, 132

632239

TVM220

109, 131

631973

OHV15 - Walbro LMK26

Jet

632688

2 CYCLE

 

 

AH/AV520 & 600, HSK600

101

632368

TVS/TVXL840

L118, L119

632463

HSK840, 845, 850/HXL840

124, 125

631026

TC200/TC300 Tillotson carburetor only.

Jet

632940

TC200/TC300 Tillotson HU112 and HU114

Jet

N/A

Do not install leaner jetted bowl nuts on engines used below four thousand feet as starting and operating problems will occur. DOING SO WILL VOID THE ENGINE WARRANTY.

4

THROTTLE CONTROL BRACKETS,

GOVERNORS AND RPM ADJUSTMENTS

Before adjusting any mixture screws, reset the screws to the recommended carburetor presets. Check for proper governor adjustments as outlined in the appropriate Technician's Handbook. Identify the locations of your high speed and low speed RPM adjustment screws. Check to make sure that the throttle control brackets are adjusted properly to allow for full choke. Always make sure that normal maintenance procedures (ie., oil, fuel, air cleaner, etc.) have been checked. Consult microfiche card #30, the computer parts look up system or Service Bulletin #107 for C.P.S.C. specifications to determine the proper RPM settings. Start the engine, allow it to warm up, the carburetor can then be adjusted for optimum performance by using the information outlined in this book. Now the low and high speed screws can be adjusted to the recommended RPM's.

HOW TO IDENTIFYA TecumsehPower CARBURETOR

TecumsehPower 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.

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.

SERIES 1 EMISSION

This carburetor is similar to the standard Series 1 carburetor. The emission equivalent has a fixed idle and main. The idle restrictor jet will be capped to prevent access unless the cap is removed. The fixed main jet is part of the bowl nut. Aball plug is visible from the bottom, which seals the passage. This carburetor also has a serviceable main nozzle emulsion tube.

5

HOW TO IDENTIFYA TecumsehPower CARBURETOR

(CONTINUED)

SERIES 2 CARBURETORS

Series 2 carburetors were used on outboard engines. This carburetor is the same as the Series 1 with the exception of the remote adjustable idle mixture screw, and a built in fuel pump.

Series 2 carburetors have a built-in fuel pump consisting of a fuel pump element which inflates and deflates with crankcase pulsations which opens and closes two flap valves in the fuel pump, thereby pumping fuel from a remote tank to the carburetor float bowl.

When replacing the fuel pump element, install with the slot opening at a 45o angle as illustrated. Installation in any other position will damage the diaphragm.

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.

SERIES 3 & SERIES 4 EMISSION

 

This carburetor is similar to the standard Series 3 & 4

 

carburetor with a few subtle differences. The emission

 

equivalent has a fixed idle and main. The idle restrictor

 

jet will be capped to prevent access unless the cap is

 

removed. The fixed main jet is part of the bowl nut. Aball

 

plug is visible from the bottom, which seals the passage.

 

This carburetor also has a serviceable main nozzle

FIXED IDLE

emulsion tube.

 

FIXED MAIN

6

HOW TO IDENTIFY A TecumsehPower CARBURETOR

(CONTINUED)

To determine whether the carburetor is a Series 3 or Series 4, look at the throttle or choke end of the carburetor.

Series 3 will have one screw on the throttle and choke plates.

The Series 4 will have two screws on the throttle and choke plates.

VECTOR CARBURETORS

The Vector carburetor is a float feed, nonadjustable carburetor, with a one piece extruded aluminum body. The float bowl, float, nozzle, and venturi are nonmetallic, which eliminates the corrosion and varnishing problems associated with similar metallic parts. Common service areas of the carburetor are contained in the fuel bowl, which include the float, needle, seat and main nozzle emulsion tube. All of these parts can be serviced without removing the carburetor body from the engine.

NOTE

If the unit was run with poor filter maintenance the venturi should be removed and the air bleeds cleaned with solvent.

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.

SERIES 3

SERIES 4

7

HOW TO IDENTIFY A TecumsehPower CARBURETOR

(CONTINUED)

SERIES 6 CARBURETORS - 2-CYCLE

Series 6 carburetors used on TVS/TVXL840 engines are similar in appearance and operation to the carburetors used on 4-cycle engines with the following differences:

1.The bowl nut is left-hand thread. This bowl nut is identified by an "L" stamped on the nut and the international left thread notches across the points.

2.A dampening spring is installed on the float hinge pin to reduce erratic float travel.

3.The two mounting bosses extend out from the carburetor body.

CUTLINE

SERIES 7 CARBURETORS (EMISSION)

The Series 7 carburetor is an emissions grade carburetor used on medium frame vertical shaft overhead valve engines. It has a non-metallic bowl and a snap-on bowl retainer to connect it to the carburetor body. This model has a fixed main jet and a fixed idle jet; both are located in the carburetor bowl. The float bowl, float, nozzle, and venturi are non-metallic, which eliminates the corrosion and varnishing problems associated with similar metallic parts. Common service areas of the carburetor are contained in the fuel bowl, which include the float, needle, seat and main nozzle emulsion tube. All of these parts can be serviced without removing the carburetor body from the engine.

SERIES 8 CARBURETOR (EMISSION)

The Series 8 carburetor has both a fixed main and idle circuit. The fixed idle system is achieved by a restrictor jet that meters the fuel for the idle circuit. The idle restrictor jet will be cappe