Kohler CH980, CH960, CH1000, CH940 User Manual

COMMAND PRO

CH940-CH980

HORIZONTAL CRANKSHAFT

SERVICE MANUAL

Section 1. Safety and General Information ............................................................................

Section 2. T ools & Aids ............................................................................................................

Section 3. Troubleshooting .....................................................................................................

Section 4. Air Cleaner and Air Intake System ........................................................................

Section 5. Fuel System and Governor....................................................................................

Section 6. Lubrication System ................................................................................................

Section 7. Electrical System and Components......................................................................

Section 8. Disassembly............................................................................................................

Section 9. Inspection and Reconditioning .............................................................................

Section 10. Reassembly ..........................................................................................................

Section 1

Safety and General Information

Section 1

Safety and General Information

Safety Precautions

To ensure safe operation please read the following statements and understand their meaning. Also refer to your equipment manufacturer's manual for other important safety information. This manual contains safety precautions which are explained below. Please read carefully.

WARNING

Warning is used to indicate the presence of a hazard that can cause severe personal injury, death, or substantial property damage if the warning is ignored.

CAUTION

Caution is used to indicate the presence of a hazard that will or can cause minor personal injury or property damage if the caution is ignored.

NOTE

Note is used to notify people of installation, operation, or maintenance information that is important but not hazard-related.

For Y our Safety!

These precautions should be followed at all times. Failure to follow these precautions could result in injury to yourself and others.

WARNING

Accidental Starts can cause severe injury or death.

Disconnect and ground spark plug leads before servicing.

Accidental Starts!

Disabling engine. Accidental starting can cause severe injury or death.

Before working on the engine or equipment, disable the engine as follows:

1) Disconnect the spark plug lead(s).

2) Disconnect negative (-) battery cable from battery.

WARNING

Rotating Parts can cause severe injury.

Stay away while engine is in operation.

Rotating Parts!

Keep hands, feet, hair, and clothing away from all moving parts to prevent injury. Never operate the engine with covers, shrouds, or guards removed.

Hot Parts can cause severe burns.

Do not touch engine while operating or just after stopping.

Hot Parts!

Engine components can get extremely hot from operation. To prevent severe burns, do not touch these areas while the engine is running - or immediately after it is turned off. Never operate the engine with heat shields or guards removed.

WARNING

1.1

Section 1 Safety and General Information

WARNING

Explosive Fuel can cause fires and severe burns.

Do not fill the fuel tank while the engine is hot or running.

Explosive Fuel!

Gasoline is extremely flammable and its vapors can explode if ignited. Store gasoline only in approved containers, in well ventilated, unoccupied buildings, away from sparks or flames. Do not fill the fuel tank while the engine is hot or running, since spilled fuel could ignite if it comes in contact with hot parts or sparks from ignition. Do not start the engine near spilled fuel. Never use gasoline as a cleaning agent.

WARNING

WARNING WARNING

Carbon Monoxide can cause severe nausea, fainting or death.

Avoid inhaling exhaust fumes, and never run the engine in a closed building or confined area.

Lethal Exhaust Gases!

Engine exhaust gases contain poisonous carbon monoxide. Carbon monoxide is odorless, colorless, and can cause death if inhaled. Avoid inhaling exhaust fumes, and never run the engine in a closed building or confined area.

Explosive Gas can cause fires and severe acid burns.

Charge battery only in a well ventilated area. Keep sources of ignition away.

Explosive Gas!

Batteries produce explosive hydrogen gas while being charged. To prevent a fire or explosion, charge batteries only in well ventilated areas. Keep sparks, open flames, and other sources of ignition away from the battery at all times. Keep batteries out of the reach of children. Remove all jewelry when servicing batteries.

Before disconnecting the negative (-) ground cable, make sure all switches are OFF. If ON, a spark will occur at the ground cable terminal which could cause an explosion if hydrogen gas or gasoline vapors are present.

Cleaning Solvents can cause severe injury or death.

Use only in well ventilated areas away from ignition sources.

Flammable Solvents!

Carburetor cleaners and solvents are extremely flammable. Keep sparks, flames, and other sources of ignition away from the area. Follow the cleaner manufacturer’s warnings and instructions on its proper and safe use. Never use gasoline as a cleaning agent.

CAUTION

Electrical Shock can cause injury.

Do not touch wires while engine is running.

Electrical Shock!

Never touch electrical wires or components while the engine is running. They can be sources of electrical shock.

1.2

Engine Identification Numbers

When ordering parts, or in any communication involving an engine, always give the Model, Specification, and Serial Numbers, including letter suffixes if there are any.

The engine identification numbers appear on a decal, or decals, affixed to the engine shrouding. See Figure 1-1. An explanation of these numbers is shown in Figure 1-2.

Section 1

Safety and General Information

Identification Decal

Figure 1-1. Engine Identification Decal Location.

A . Model No.

Command Engine Horizontal Crankshaft Numerical Designation

B. Spec. No.

C. Serial No.

Year Manufactured Code Code Year

37 2007 38 2008

C H 980 S

Version Code

S = Electric Start

CH940-0001 CH960-0001 CH980- 0001

Complete Spec. Number (Incorporating Model No. with V ariation No. of Basic Spec.)

3705810334

Factory Code

Figure 1-2. Explanation of Engine Identification Numbers.

1.3

Section 1 Safety and General Information

Oil Recommendations

Using the proper type and weight of oil in the crankcase is extremely important. So is checking oil daily and changing oil regularly. It is also recommended that a consistent brand of oil be used. Failure to use the correct oil, or using dirty oil, causes premature engine wear and failure.

Oil Type

Use high-quality detergent oil of API (American Petroleum Institute) Service Class SG, SH, SJ or higher. Select the viscosity based on the air

temperature at the time of operation as shown in the following table.

RECOMMENDED SAE VISCOSITY GRADES

10W-30

5W-20, 5W-30

°F -20 0 20 32 40 60 80 100

°C -30 -20 -10 0 10 20 30 40

TEMPERATURE RANGE EXPECTED BEFORE NEXT OIL CHANGE

* Use of synthetic oil having 5W-20 or 5W-30 rating is acceptable,

up to 4°C (40°F)

** Synthetic oils will provide better starting in extreme cold below

23°C (-10°F)

NOTE: Using other than service class SG, SH, SJ or

higher oil or extending oil change intervals longer than recommended can cause engine damage.

NOTE: Synthetic oils meeting the listed

classifications may be used with oil changes performed at the recommended intervals. However, to allow piston rings to properly seat, a new or rebuilt engine should be operated for at least 50 hours using standard petroleum based oil before switching to synthetic oil.

A logo or symbol on oil containers identifies the API service class and SAE viscosity grade. See Figure 1-3.

Kohler 10W-30

Refer to Section 6 - Lubrication System for detailed procedures on checking the oil, changing the oil and changing the oil filter.

Fuel Recommendations

WARNING: Explosive Fuel!

Gasoline is extremely flammable and its vapors can explode if ignited. Before servicing the fuel system, make sure there are no sparks, open flames or other sources of ignition nearby as these can ignite gasoline vapors. Disconnect and ground the spark plug leads to prevent the possibility of sparks from the ignition system.

General Recommendations

Purchase gasoline in small quantities that can be used within 30 days, and store only in clean, approved containers. Do not use gasoline left over from the previous season, unless treated with a fuel stabilizer (see Storage), to minimize gum deposits and ensure easy starting. Do not use gasoline containing Methanol, or add oil to the gasoline.

Do not overfill the fuel tank. Leave room for the fuel to expand.

Fuel Type

For best results, use only clean, fresh, unleaded gasoline with a pump sticker octane rating of 87 or higher. In countries using the Research method, it should be 90 octane minimum.

Unleaded gasoline is recommended as it leaves less combustion chamber deposits and reduces harmful exhaust emissions. Leaded gasoline is not recommended and must not be used on EFI engines, or on other models where exhaust emissions are regulated.

Gasoline/Alcohol Blends

Gasohol (up to 10% ethyl alcohol, 90% unleaded gasoline by volume) is approved as a fuel for Kohler engines. Other gasoline/alcohol blends including E20 and E85 are not to be used and not approved. Any failures resulting from use of these fuels will not be warranted.

Figure 1-3. Oil Container Logo.

1.4

Gasoline/Ether Blends

Methyl Tertiary Butyl Ether (MTBE) and unleaded gasoline blends (up to a maximum of 15% MTBE by volume) are approved as a fuel for Kohler engines. Other gasoline/ether blends are not approved.

Periodic Maintenance Instructions

Section 1

Safety and General Information

WARNING: Accident al St arts!

Disabling engine. Accidental starting can cause severe injury or death. Before working on the engine or equipment, disable the engine as follows: 1) Disconnect the spark plug lead(s). 2) Disconnect negative (-) battery cable from battery.

Maintenance Schedule

These required maintenance procedures should be performed at the frequency stated in the table. They should also be included as part of any seasonal tune-up.

Frequency

Daily or Before

Starting Engine

Weekly

Seasonally or

Every 150 Hours

Every 200 Hours

Seasonally or

Every 300 Hours

Yearly or

Every 500 Hours

Every 600 Hours

¹Perform these maintenance procedures more frequently under extremely dusty, dirty conditions.

Have a Kohler Engine Service Dealer perform this service.

Maintenance Refer to:

• Fill fuel tank. Section 5

• Check oil level. Section 6

• Check air cleaner for dirty1, loose, or damaged parts. Section 4

• Check air intake and cooling areas, clean as necessary. Section 4

• Check filter minder or air cleaner element. Section 4

• Check air cleaner element. Section 4

• Replace fuel filter. Section 5

• Change oil. Oil filter is recommended. (More frequently under severe conditions.) Section 6

• Remove cooling shrouds and clean cooling areas1. Section 4

• Check oil cooler fins, clean as necessary. Section 6

• Check spark plug condition and gap. Section 7

• Change oil filter. Section 6

• Replace air cleaner element. Section 4

• Have solenoid shift starter disassembled and cleaned2. Section 7

• Have crankshaft splines lubricated2.

• Replace inner air cleaner element. Section 4

• Replace spark plugs. Section 7

Storage

If the engine will be out of service for 30 days or more, use the following storage procedure.

1. Clean the exterior surfaces of the engine. Avoid spraying water at the wiring harness or any of the electrical components.

2. Change the oil and oil filter while the engine is still warm from operation. See Changing Oil and Oil Filter in Section 6.

3. The fuel system must be completely emptied, or the gasoline must be treated with a stabilizer to prevent deterioration. If you choose to use a stabilizer, follow the manufacturer’s recommendations, and add the correct amount for the capacity of the fuel system.

Fill the fuel tank with clean, fresh gasoline. Run the engine for 2 to 3 minutes to get stabilized fuel into the rest of the system. Close the fuel shut-off valve when the unit is being stored or transported.

To empty the system, run the engine until the tank and the system are empty.

4. Remove the spark plugs and add one tablespoon of engine oil into each spark plug hole. Install the spark plugs, but do not connect the plug leads. Crank the engine two or three revolutions.

5. Disconnect the battery or use a battery minder to keep the battery charged during storage.

6. Store the engine in a clean, dry place.

1.5

Section 1 Safety and General Information

Dimensions in millimeters. Inch equivalents shown in [ ].

Figure 1-4. T ypical CH PRO Series Engine Dimensions with Heavy-Duty Air Cleaner.

1.6

Safety and General Information

General Specifications¹

Power (@ 3600 RPM, exceeds Society of Automotive Engineers-Small Engine Test Code J1940.)

CH940 ........................................................................................................25.4 kW (34 HP)

CH960 ........................................................................................................26.9 kW (36 HP)

CH980 ........................................................................................................28.3 kW (38 HP)

Bore ...................................................................................................................90 mm (3.54 in.)

Stroke ................................................................................................................ 78.5 mm (3.1 in.)

Displacement ...................................................................................................999 cc (61 cu. in.)

Compression Ratio ......................................................................................... 8.8:1

Dry Weight ......................................................................................................59.8 kg (132 lb.)

Oil Capacity (w/filter) - approximate,

determined by oil filter used ........................................................................ 2.7 L (2.9 U.S. qt.)

Angle of Operation - Maximum (At Full Oil Level) All Directions ......... 25°

Section 1

Blower Housing and Sheet Metal

M6 Shoulder Screw Torque

New, Untapped Hole (casting) .............................................................. 10.7 N·m (95 in. lb.)

Used, Tapped Hole (casting) ................................................................... 7.3 N·m (65 in. lb.)

New, Extruded Hole (sheet metal) ........................................................ 4.0 N·m (35 in. lb.)

Used, Extruded Hole (sheet metal) ........................................................ 2.0 N·m (17.7 in. lb.)

Mounting Clip (valley baffle)................................................................. 2.5 N·m (22.1 in. lb.)

M6 Screw Torque

New, Untapped Hole (casting) .............................................................. 10.7 N·m (95 in. lb)

Used, Tapped Hole (casting) ...................................................................7.3 N·m (65 in. lb)

Rectifier-Regulator Fastener Torque ........................................................... 2.0 N·m (18 in. lb.)

Oil Cooler Fastener Torque ............................................................................ 2.2 N·m (20 in. lb.)

Camshaft

End Play ...........................................................................................................0.3/1.3 mm (0.011/0.051 in.)

Running Clearance ......................................................................................... 0.025/0.063 mm (0.0010/0.0025 in.)

Bore I.D.

New ........................................................................................................... 20.000/20.025 mm (0.7874/0.7884 in.)

Max. Wear Limit ...................................................................................... 20.038 mm (0.7889 in.)

Camshaft Bearing Surface O.D.

New ........................................................................................................... 19.962/19.975 mm (0.7859/0.7864 in.)

Max. Wear Limit ...................................................................................... 19.959 mm (0.7858 in.)

Cam Lobe Profile (Minimum Dimension, Measured From Base Circle To Top Of Lobe)

Exhaust ............................................................................................................. 35 mm (1.3779 in.)

Intake ................................................................................................................35 mm (1.3779 in.)

¹Values are in Metric units. Values in parentheses are English equivalents. Lubricate threads with engine oil

prior to assembly.

1.7

Section 1 Safety and General Information

Carburetor, Intake Manifold, and Air Cleaner

Intake Manifold Mounting Fastener Torque

Torque (Using Sequence) in Two Stages ...............................................first to 16.9 N·m (150 in. lb.)

finally to 22.6 N·m (200 in. lb.)

Carburetor/Air Cleaner Mounting Nut Torque .........................................7.9 N·m (70 in. lb.)

Air Cleaner Mounting Screw Torque (Into Intake Manifold) ...................9.9 N·m (88 in. lb.)

Control Bracket

Mounting Screw (Into Intake Manifold from Air Cleaner) Torque ......... 9.9 N·m (88 in. lb.)

Connecting Rod

Cap Fastener Torque (Torque In Increments) ............................................. 11.3 N·m (100 in. lb.)

Crankpin End I.D. @ 70°F

New ........................................................................................................... 44.030/44.037 mm (1.7334/1.7337 in.)

Max. Wear Limit ...................................................................................... 0.070 mm (0.0028 in.)

Connecting Rod-to-Crankpin Running Clearance

New ........................................................................................................... 0.030/0.055 mm (0.0012/0.0022 in.)

Max. Wear Limit ...................................................................................... 0.070 mm (0.0028 in.)

Connecting Rod-to-Crankpin Side Clearance ............................................ 0.30/0.59 mm (0.0118/0.0232 in.)

Connecting Rod-to-Piston Pin Running Clearance................................... 0.015/0.028 mm (0.0006/0.0011 in.)

Piston Pin End I.D. @ 70°F

New ........................................................................................................... 19.023/19.015 mm (0.7489/0.7486 in.)

Max. Wear Limit ...................................................................................... 19.036 mm (0.7494 in.)

Crankcase

Governor Cross Shaft Bore I.D.

New ........................................................................................................... 8.025/8.050 mm (0.3159/0.3169 in.)

Max. Wear Limit ...................................................................................... 8.088 mm (0.3184 in.)

Breather Cover Fastener Torque .................................................................. 5.7 N·m (51 in. lb.)

Oil Drain Plug Torque .................................................................................... 21.4 N·m (15.7 ft. lb.)

Closure Plate

Closure Plate Fastener Torque ...................................................................... 24.4 N·m (216 in. lb.)

Reservoir (Oil)

Mounting Screw Torque ................................................................................ 24.4 N·m (216 in. lb.)

Crankshaft

End Play (Free) ................................................................................................ 0.30/1.50 mm (0.011/0.059 in.)

Crankshaft Bore (In Crankcase)

New, Without Main Bearing ................................................................. 50.00/50.025 mm (1.9685/1.969 in.)

With Main Bearing Installed .................................................................45.040/45.145 mm (1.7732/1.7773 in.)

Max. Wear Limit ...................................................................................... 45.158 mm (1.7778 in.)

Crankshaft to Sleeve Bearing (In Crankcase)

Running Clearance - New ...................................................................... 0.040/0.167 mm (0.0015/0.0065 in.)

1.8

Section 1

Safety and General Information

Crankshaft Bore (In Closure Plate) - New, Without Bearing ................... 50.025/50.00 mm (1.9694/1.9685 in.)

Crankshaft to Sleeve Bearing (In Closure Plate)

Running Clearance - New ...................................................................... 0.040/0.167 mm (0.0015/0.0065 in.)

Flywheel End Main Bearing Journal

O.D. - New ................................................................................................ 44.978/45.00 mm (1.770/1.771 in.)

O.D. - Max. Wear Limit ........................................................................... 44.90 mm (1.767 in.)

Max. Taper ................................................................................................0.022 mm (0.0009 in.)

Max. Out-of-Round ................................................................................. 0.025 mm (0.0010 in.)

Closure Plate End Main Bearing Journal

O.D. - New ................................................................................................ 44.978/45.00 mm (1.770/1.771 in.)

O.D. - Max. Wear Limit ........................................................................... 44.90 mm (1.767 in.)

Max. Taper ................................................................................................0.022 mm (0.0009 in.)

Max. Out-of-Round ................................................................................. 0.025 mm (0.0010 in.)

Connecting Rod Journal

O.D. - New ................................................................................................ 43.982/44.000 mm (1.731/1.732 in.)

O.D. - Max. Wear Limit ........................................................................... 43.97 mm (1.731 in.)

Max. Taper ................................................................................................0.018 mm (0.0007 in.)

Max. Out-of-Round ................................................................................. 0.025 mm (0.0010 in.)

Width ........................................................................................................53.00/53.09 mm (2.0866/2.0901 in.)

Crankshaft T .I.R.

PTO End, Crank in Engine ......................................................................0.279 mm (0.0110 in.)

Entire Crank, in V-Blocks ....................................................................... 0.10 mm (0.0039 in.)

Cylinder Bore

Cylinder Bore I.D.

New ........................................................................................................... 90.000/90.025 mm (3.543/3.544 in.)

Max. Wear Limit ...................................................................................... 90.075 mm (3.546 in.)

Max. Out-of-Round ................................................................................. 0.013 mm (0.00051 in.)

Max. Taper ................................................................................................ 0.013 mm (0.00051 in.)

Main Bearing I.D. (Crankcase/Closure Plate)

New (Installed) ........................................................................................ 45.040/45.145 mm (1.773/1.777 in.)

Max. Wear Limit ......................................................................................45.158 mm

Cylinder Head

Cylinder Head Fastener Torque

Head Bolt - Torque in Two Stages ......................................................... first to 22.6 N·m (200 in. lb.)

finally to 45.2 N·m (400 in. lb.)

Max. Out-of-Flatness ...................................................................................... 0.076 mm (0.003 in.)

Pipe Plug (3/4") Torque ................................................................................... 28.25 N·m (250 in. lb.)

Rocker Arm Screw Torque ............................................................................ 14.6 N·m (130 in. lb.)

Fan/Flywheel

Fan Fastener Torque .......................................................................................9.9 N·m (88 in. lb.)

Flywheel Retaining Screw Torque ............................................................... 67.8 N·m (50 ft. lb.)

1.9

Section 1 Safety and General Information

Grass Screen

Hex Stud Torque .............................................................................................. 9.9 N·m (88 in. lb.)

Mounting Screw Torque ................................................................................ 9.9 N·m (88 in. lb.)

Front Drive Shaft Screw Torque (Into Flywheel) ....................................... 24.4 N·m (216 in. lb.)

Governor

Governor Cross Shaft-to-Crankcase Running Clearance ........................ 0.025/0.087 mm (0.0009/0.0034 in.)

Governor Cross Shaft O.D.

New ........................................................................................................... 7.963/8.000 mm (0.3135/0.3149 in.)

Max. Wear Limit ...................................................................................... 7.936 mm (0.3124 in.)

Governor Gear Shaft-to-Governor Gear Running Clearance .................0.070/0.160 mm (0.0027/0.0063 in.)

Governor Gear Shaft O.D.

New ........................................................................................................... 5.990/6.000 mm (0.2358/0.2362 in.)

Max. Wear Limit ...................................................................................... 5.977 mm (0.2353 in.)

Governor Lever Nut Torque ......................................................................... 7.3 N·m (65 in. lb.)

Ignition

Spark Plug Type (Champion® or Equivalent) ............................................. XC10YC

Spark Plug Gap ............................................................................................... 0.76 mm (0.030 in.)

Spark Plug Torque .......................................................................................... 24.4-29.8 N·m (18-22 ft. lb.)

Ignition Module Air Gap ...............................................................................0.28/0.33 mm (0.011/0.013 in.)

Ignition Module Fastener Torque ................................................................. 6.2 N·m (55 in. lb.) into new holes, or

4.0 N·m (35 in. lb.) into used holes

Lifter Feed Chamber

Cover/Baffle Screw Torque ............................................................................ 6.2 N·m (55 in. lb.)

Muffler

Muffler Retaining Nut Torque ...................................................................... 24.4 N·m (216 in. lb.)

Oil Cooler

Mounting Screws Torque .............................................................................. 3.9 N·m (35 in. lb.)

Oil Filter

Oil Filter Torque .............................................................................................. 3/4-1 turn after gasket contact

Oil Filter Adapter/Housing

Mounting Screw Torque ................................................................................ 24.4 N·m (216 in. lb.)

Piston, Piston Rings, and Piston Pin

Piston-to-Piston Pin Running Clearance .................................................... 0.006/0.018 mm (0.0002/0.0007 in.)

Piston Pin Bore I.D.

New ........................................................................................................... 19.006/17.013 mm (0.7482/0.7485 in.)

Max. Wear Limit ...................................................................................... 19.025 mm (0.7490 in.)

Piston Pin O.D.

New ........................................................................................................... 18.995/19.000 mm (0.7478/0.7480 in.)

Max. Wear Limit ...................................................................................... 18.994 mm (0.7478 in.)

1.10

Section 1

Safety and General Information

Top Compression Ring-to-Groove Side Clearance .................................... 0.04/0.08 mm (0.0015/0.0031 in.)

Middle Compression Ring-to-Groove Side Clearance .............................. 0.04/0.08 mm (0.0015/0.0031 in.)

Oil Control Ring-to-Groove Side Clearance ...............................................0.03/0.19 mm (0.0011/0.0074 in.)

Top and Center Compression Ring End Gap

New Bore ..................................................................................................0.30/0.55 mm (0.011/0.021 in.)

Used Bore (Max.) ...................................................................................... 0.94 mm (0.037 in.)

Piston Thrust Face O.D.²

New ........................................................................................................... 89.953/89.967 mm (3.5414/3.5420 in.)

Max. Wear Limit ...................................................................................... 89.925 mm (3.540 in.)

Piston Thrust Face-to-Cylinder Bore² Running Clearance

New ........................................................................................................... 0.033/0.72 mm (0.0013/0.0028 in.)

Starter Assembly

Thru Bolt Torque

Delco-Remy (Solenoid Shift) .................................................................. 5.6-9.0 N·m (49-79 in. lb.)

Mounting Screw Torque ................................................................................ 15.3 N·m (135 in. lb.)

Brush Holder Mounting Screw Torque

Delco-Remy Starter ................................................................................. 2.5-3.3 N·m (22-29 in. lb.)

Solenoid (Starter)

Mounting Hardware Torque

Delco-Remy Starter ................................................................................. 4.0-6.0 N·m (35-53 in. lb.)

Nut, Positive (+) Brush Lead Torque

Delco-Remy Starter ................................................................................. 8.0-11.0 N·m (71-97 in. lb.)

Stator

Mounting Screw Torque ................................................................................ 6.2 N·m (55 in. lb.)

Throttle/Choke Control Bracket

Fastener Torque ............................................................................................... 9.9 N·m (88 in. lb.)

Valve Cover

Valve Cover Fastener Torque ........................................................................ 7.9 N·m (70 in. lb.)

Valves and Valve Lifters

Hydraulic Valve Lifter to Crankcase Running Clearance ........................ 0.012/0.050 mm (0.0004/0.0019 in.)

Intake Valve Stem-to-Valve Guide Running Clearance ........................... 0.038/0.076 mm (0.0015/0.0030 in.)

Exhaust Valve Stem-to-Valve Guide Running Clearance ........................0.050/0.088 mm (0.0020/0.0035 in.)

Intake Valve Guide I.D.

New ........................................................................................................... 7.038/7.058 mm (0.2771/0.2779 in.)

Max. Wear Limit ...................................................................................... 7.135 mm (0.2809 in.)

Exhaust Valve Guide I.D.

New ........................................................................................................... 7.038/7.058 mm (0.2771/0.2779 in.)

Max. Wear Limit ...................................................................................... 7.159 mm (0.2819 in.)

²Measure 11 mm (0.433 in.) above the bottom of the piston skirt at right angles to the piston pin.

1.11

Section 1 Safety and General Information

Valve Guide Reamer Size

Standard ...................................................................................................7.048 mm (0.2775 in.)

0.25 mm O.S. ............................................................................................. 7.298 mm (0.2873 in.)

Nominal Valve Face Angle ............................................................................45°

General Torque Values

Metric Fastener T orque Recommendations for S tandard Applications

Tightening Torque: N·m (in. lb.) + or - 10%

Property Class

Noncritical

Fasteners

4.8

Size M4 1.2 (11) 1.7 (15) 2.9 (26) 4.1 (36) 5.0 (44) 2.0 (18) M5 2.5 (22) 3.2 (28) 5.8 (51) 8.1 (72) 9.7 (86) 4.0 (35) M6 4.3 (38) 5.7 (50) 9.9 (88) 14.0 (124) 16.5 (146) 6.8 (60) M8 10.5 (93) 13.6 (120) 24.4 (216) 33.9 (300) 40.7 (360) 17.0 (150)

5.8

8.8 10.9 12.9

Into Aluminum

Tightening Torque: N·m (ft. lb.) + or - 10%

Property Class

Noncritical

Fasteners

4.8

M10 21.7 (16) 27.1 (20) 47.5 (35) 66.4 (49) 81.4 (60) 33.9 (25) M12 36.6 (27) 47.5 (35) 82.7 (61) 116.6 (86) 139.7 (103) 61.0 (45) M14 58.3 (43) 76.4 (55) 131.5 (97) 184.4 (136) 219.7 (162) 94.9 (70)

5.8

8.8

10.9

12.9

Into Aluminum

1.12

Safety and General Information

English Fastener T orque Recommendations for St andard Applications

Section 1

Tightening Torque: N·m (in. lb.) + or - 20%

Bolts, Screws, Nuts and Fasteners Assembled Into Cast Iron or Steel

Grade 2 Grade 5 Grade 8

Size 8-32 2.3 (20) 2.8 (25) --------- 2.3 (20) 10-24 3.6 (32) 4.5 (40) --------- 3.6 (32) 10-32 3.6 (32) 4.5 (40) --------- --------- 1/4-20 7.9 (70) 13.0 (115) 18.7 (165) 7.9 (70) 1/4-28 9.6 (85) 15.8 (140) 22.6 (200) --------- 5/16-18 17.0 (150) 28.3 (250) 39.6 (350) 17.0 (150) 5/16-24 18.7 (165) 30.5 (270) --------- --------- 3/8-16 29.4 (260) --------- --------- --------- 3/8-24 33.9 (300) --------- --------- ---------

Grade 2 or 5 Fasteners Into Aluminum

Tightening Torque: N·m (ft. lb.) + or - 20%

Size 5/16-24 --------- ---------- 40.7 (30) --------3/8-16 --------- 47.5 (35) 67.8 (50) --------3/8-24 --------- 54.2 (40) 81.4 (60) --------7/16-14 47.5 (35) 74.6 (55) 108.5 (80) --------7/16-20 61.0 (45) 101.7 (75) 142.4 (105) --------1/2-13 67.8 (50) 108.5 (80) 155.9 (115) --------1/2-20 94.9 (70) 142.4 (105) 223.7 (165) --------9/16-12 101.7 (75) 169.5 (125) 237.3 (175) --------9/16-18 135.6 (100) 223.7 (165) 311.9 (230) --------5/8-11 149.2 (110) 244.1 (180) 352.6 (260) --------5/8-18 189.8 (140) 311.9 (230) 447.5 (330) --------3/4-10 199.3 (150) 332.2 (245) 474.6 (350) --------3/4-16 271.2 (200) 440.7 (325) 637.3 (470) ---------

Torque

Conversions

N·m = in. lb. x 0.113 N·m = ft. lb. x 1.356 in. lb. = N·m x 8.85 ft. lb. = N·m x 0.737

1.13

Section 2

Tools & Aids

Section 2

Tools & Aids

Certain quality tools are designed to help you perform specific disassembly, repair, and reassembly procedures. By using tools designed for the job, you can properly service engines easier, faster, and safer! In addition, you’ll increase your service capabilities and customer satisfaction by decreasing engine downtime.

Here is the list of tools and their source.

Separate Tool Suppliers:

Kohler Tools Contact your source of supply.

SE Tools 415 Howard St. Lapeer, MI 48446 Phone 810-664-2981 Toll Free 800-664-2981 Fax 810-664-8181

Design Technology Inc. 768 Burr Oak Drive Westmont, IL 60559 Phone 630-920-1300

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2.3

Section 2 Tools & Aids

Special Tools You Can Make

Flywheel Holding Tool

A flywheel holding tool can be made out of an old junk flywheel ring gear as shown in Figure 2-1, and used in place of a strap wrench.

1. Using an abrasive cut-off wheel, cut out a six tooth segment of the ring gear as shown.

2. Grind off any burrs or sharp edges.

3. Invert the segment and place it between the ignition bosses on the crankcase so the tool teeth engage the flywheel ring gear teeth. The bosses will lock the tool and flywheel in position for loosening, tightening, or removing with a puller.

2. Remove the studs of a Posi-Lock rod or grind off the aligning steps of a Command rod, so the joint surface is flat.

3. Find a 1 in. long capscrew with the correct thread size to match the threads in the connecting rod.

4. Use a flat washer with the correct I.D. to slip on the capscrew and approximately 1” O.D. (Kohler Part No. 12 468 05-S). Assemble the capscrew and washer to the joint surface of the rod, as shown in Figure 2-2.

Figure 2-1. Flywheel Holding Tool.

Rocker Arm/Crankshaft Tool

A spanner wrench to lift the rocker arms or turn the crankshaft may be made out of an old junk connecting rod.

1. Find a used connecting rod from a 10 HP or larger engine. Remove and discard the rod cap.

Figure 2-2. Rocker Arm/Crankshaf t T ool.

2.4

Section 3

Troubleshooting

Section 3

Troubleshooting

Troubleshooting Guide

When troubles occur, be sure to check the simple causes which, at first, may seem too obvious to be considered. For example, a starting problem could be caused by an empty fuel tank.

Some general common causes of engine troubles are listed below. Use these to locate the causing factors. Refer to the specific section(s) within this service manual for more detailed information.

Engine Cranks But Will Not Start

1. Empty fuel tank.

2. Fuel shut-off valve closed.

3. Poor fuel, dirt, or water in the fuel system.

4. Clogged fuel line.

5. Spark plug lead(s) disconnected.

6. Kill switch in off position.

7. Faulty spark plugs.

8. Faulty ignition module(s).

9. Carburetor solenoid malfunction.

10. Battery connected backwards.

11. Safety interlock system engaged.

11. Quality of fuel.

12. Flywheel key sheared.

13. Intake system leak.

Engine Will Not Crank

1. PTO drive is engaged.

2. Battery is discharged.

3. Safety interlock switch is engaged.

4. Loose or faulty wires or connections.

5. Faulty key switch or ignition switch.

6. Faulty electric starter or solenoid.

7. Seized internal engine components.

Engine Runs But Misses

1. Dirt or water in the fuel system.

2. Spark plug lead disconnected.

3. Poor quality of fuel.

4. Faulty spark plug(s).

5. Loose wires or connections that intermittently ground the ignition kill circuit.

6. Engine overheated.

7. Faulty ignition module or incorrect air gap.

8. Carburetor adjusted incorrectly.

Engine Starts But Does Not Keep Running

1. Restricted fuel tank cap vent.

2. Poor fuel, dirt, or water in the fuel system.

3. Faulty or misadjusted choke or throttle controls.

4. Loose wires or connections that short the kill terminal of ignition module to ground.

5. Faulty cylinder head gasket.

6. Faulty carburetor.

7. Intake system leak.

Engine Starts Hard

1. PTO drive is engaged.

2. Dirt or water in the fuel system.

3. Clogged fuel line.

4. Loose or faulty wires or connections.

5. Faulty or misadjusted choke or throttle controls.

6. Faulty spark plugs.

7. Low compression.

8. Weak spark.

9. Fuel pump malfunction causing lack of fuel.

10. Engine overheated-cooling/air circulation restricted.

Engine Will Not Idle

1. Dirt or water in the fuel system.

2. Stale fuel and/or gum in carburetor.

3. Faulty spark plugs.

4. Fuel supply inadequate.

5. Idle fuel adjusting needles improperly set.

6. Idle speed adjusting screw improperly set.

7. Low compression.

8. Restricted fuel tank cap vent.

9. Engine overheated-cooling system/air circulation problem.

Engine Overheats

1. Air intake/grass screen, cooling fins, or cooling shrouds clogged.

2. Excessive engine load.

3. Low crankcase oil level.

4. High crankcase oil level.

5. Faulty carburetor.

6. Lean fuel mixture.

3.1

Section 3 Troubleshooting

Engine Knocks

1. Excessive engine load.

2. Low crankcase oil level.

3. Old or improper fuel.

4. Internal wear or damage.

5. Hydraulic lifter malfunction.

6. Quality of fuel.

7. Incorrect grade of oil.

Engine Loses Power

1. Low crankcase oil level.

2. High crankcase oil level.

3. Dirty air cleaner element.

4. Dirt or water in the fuel system.

5. Excessive engine load.

6. Engine overheated.

7. Faulty spark plugs.

8. Low compression.

9. Exhaust restriction.

10. Low battery.

11. Incorrect governor setting.

Engine Uses Excessive Amount of Oil

1. Incorrect oil viscosity/type.

2. Clogged, broken, or inoperative crankcase breather.

3. Worn or broken piston rings.

4. Worn cylinder bore.

5. Worn valve stems/valve guides.

6. Crankcase overfilled.

7. Blown head gasket/overheated.

Oil Leaks from Oil Seals, Gaskets

1. Clogged, broken or inoperative crankcase breather.

2. Loose or improperly torqued fasteners.

3. Piston blowby, or leaky valves.

4. Restricted exhaust.

External Engine Inspection

Before cleaning or disassembling the engine, make a thorough inspection of its external appearance and condition. This inspection can give clues to what might be found inside the engine (and the cause) when it is disassembled.

• Check for buildup of dirt and debris on the crankcase, cooling fins, grass screen, and other external surfaces. Dirt or debris on these areas are causes of higher operating temperatures and overheating.

• Check the air cleaner cover and base for damage or indications of improper fit and seal.

• Check the air cleaner element. Look for holes, tears, cracked or damaged sealing surfaces, or other damage that could allow unfiltered air into the engine. Also note if the element is dirty or clogged. These could indicate that the engine has been under serviced.

• Check the carburetor throat for dirt. Dirt in the throat is further indication that the air cleaner is not functioning properly.

• Check the oil level. Note if the oil level is within the operating range on the dipstick, or if it is low or overfilled.

• Check the condition of the oil. Drain the oil into a container - the oil should flow freely. Check for metal chips and other foreign particles.

Sludge is a natural by-product of combustion; a small accumulation is normal. Excessive sludge formation could indicate overrich carburetion, weak ignition, overextended oil change intervals or wrong weight or type of oil was used, to name a few.

NOTE: It is good practice to drain oil at a

location away from the workbench. Be sure to allow ample time for complete drainage.

Cleaning the Engine

After inspecting the external condition of the engine, clean the engine thoroughly before disassembling it. Also clean individual components as the engine is disassembled. Only clean parts can be accurately inspected and gauged for wear or damage. There are many commercially available cleaners that will quickly remove grease, oil, and grime from engine parts. When such a cleaner is used, follow the manufacturer’s instructions and safety precautions carefully.

Make sure all traces of the cleaner are removed before the engine is reassembled and placed into operation. Even small amounts of these cleaners can quickly break down the lubricating properties of engine oil.

• Check for obvious fuel and oil leaks, and damaged components. Excessive oil leakage can indicate a clogged or improperly-assembled breather, worn/damaged seals and gaskets, or loose or improperly-torqued fasteners.

3.2

Section 3

Troubleshooting

Basic Engine Tests

Crankcase Vacuum T est

A partial vacuum should be present in the crankcase when the engine is operating. Pressure in the crankcase (normally caused by a clogged or improperly assembled breather) can cause oil to be forced out at oil seals, gaskets, or other available spots.

Crankcase vacuum is best measured with either a water manometer or a vacuum gauge (see Section 2). Complete instructions are provided in the kits.

To test the crankcase vacuum with the manometer:

1. Insert the stopper/hose into the oil fill hole. Leave the other tube of manometer open to atmosphere. Make sure the shut off clamp is closed.

2. Start the engine and run at no-load high speed (3200 to 3750 RPM).

3. Open the clamp and note the water level in the tube.

The level in the engine side should be a minimum of 10.2 cm (4 in.) above the level in the open side.

If the level in the engine side is less than specified (low/no vacuum), or the level in the engine side is lower than the level in the open side (pressure), check for the conditions in the table below.

4. Close the shut-off clamp before stopping the

engine.

To test the crankcase vacuum with the Vacuum/ Pressure Gauge Kit (see Section 2):

1. Remove the dipstick or oil fill plug/cap.

2. Install the adapter into the oil fill/dipstick tube opening.

3. Push the barbed fitting on the gauge solidly into the hole in the adapter.

4. Start the engine and bring it up to operating speed (3200-3600 RPM).

5. Check the reading on the gauge. If the reading is to the left of 0 on the gauge, vacuum or negative pressure is indicated. If the reading is to the right of 0 on the gauge, positive pressure is present.

Crankcase vacuum should be a minimum of 4 inches of water. If the reading is below the specification, or if pressure is present, check the table below for possible causes and remedies.

No Crankcase Vacuum/Pressure in Crankcase

Possible Cause

1. Crankcase breather clogged or inoperative.

2. Seals and/or gaskets leaking. Loose or improperly torqued fasteners.

3. Piston blow by or leaky valves (confirm by inspecting components).

4. Restricted exhaust.

Solution

1. Disassemble breather, clean parts thoroughly, reassemble, and recheck pressure.

2. Replace all worn or damaged seals and gaskets. Make sure all fasteners are tightened securely. Use appropriate torque values and sequences when necessary.

3. Recondition piston, rings, cylinder bore, valves, and valve guides.

4. Repair/replace restricted muffler/exhaust system.

3.3

Section 3 Troubleshooting

Compression T est

A compression test is best performed on a warm engine. Clean any dirt or debris away from the base of the spark plugs before removing them. Be sure the choke is off, and the throttle is wide open during the test. Compression should be at least 160 psi and should not vary more than 15% between cylinders.

Cylinder Leakdown T est

A cylinder leakdown test can be a valuable alternative to a compression test. By pressurizing the combustion chamber from an external air source, you can determine if the valves or rings are leaking and how badly.

The Cylinder Leakdown Tester (see Section 2) is a relatively simple, inexpensive leakdown tester for small engines. The tester includes a quick disconnect for attaching the adapter hose, and a holding tool.

Leakdown T est Instructions

1. Run the engine for 3-5 minutes to warm it up.

2. Remove the spark plug(s) and the air filter from engine.

3. Rotate the crankshaft until the piston (of cylinder being tested) is at top dead center (TDC) of the compression stroke. Hold the engine in this position while testing. The holding tool supplied with the tester can be used if the PTO end of the crankshaft is accessible. Lock the holding tool onto the crankshaft. Install a 3/8" breaker bar into the hole/slot of the holding tool, so it is perpendicular to both the holding tool and crankshaft PTO.

If the flywheel end is more accessible, use a breaker bar and socket on the flywheel nut/screw to hold it in position. An assistant may be needed to hold the breaker bar during testing. If the engine is mounted in a piece of equipment, it may be possible to hold it by clamping or wedging a driven component. Just be certain that the engine cannot rotate off of TDC in either direction.

4. Install the adapter into the spark plug hole, but do not attach it to the tester at this time.

5. Connect an air source of at least 50 psi to the tester.

6. Turn the regulator knob in the increase direction (clockwise) until the gauge needle is in the yellow set area at the low end of the scale.

7. Connect the tester quick-disconnect to the adapter hose while firmly holding the engine at TDC. Note the gauge reading and listen for escaping air at the carburetor intake, exhaust outlet, and crankcase breather.

8. Check the test results against the following table:

Leakdown Test Results

Air escaping from crankcase breather ......................................................Rings or cylinder worn.

Air escaping from exhaust system ............................................................Defective exhaust valve/improper seating.

Air escaping from carburetor .....................................................................Defective intake valve/improper seating.

Gauge reading in low (green) zone ............................................................ Piston rings and cylinder in good

condition.

Gauge reading in moderate (yellow) zone ...............................................Engine is still usable, but there is some

wear present. Customer should start planning for overhaul or replacement.

Gauge reading in high (red) zone ...............................................................Rings and/or cylinder have considerable

wear. Engine should be reconditioned or replaced.

3.4

Air Cleaner and Air Intake System

Section 4

Air Cleaner and Air Intake System

Section 4

Air Cleaners

General

These engines use a heavy-duty style air cleaner as shown in Figure 4-1, consisting of a cylindrical housing attached to the carburetor and intake manifold. The air cleaner housing contains a paper element and inner element, designed for longer service intervals. The system is CARB/EPA certified and the components should not be altered or modified in any way.

Heavy-Duty Style Air Cleaner

2. Check and clean the screen area on the inlet side. Pull the air cleaner paper element out of the housing on opposite side. See Figures 4-2 and 4-3.

Inlet Screen

Figure 4-2. Accessing Inlet Screen.

Paper Element

Figure 4-1. Heavy-Duty Style Air Cleaner.

Service

Weekly and every 150 hours: Check filter minder (if equipped), unhook the two retaining clips on each end and remove the end caps. Perform inspection of the paper element and inlet screen area.

Seasonally or every 300 hours of operation (more often under extremely dusty or dirty conditions), replace the paper element and check the inner element. Follow these steps.

1. Unhook the two retaining clips on each end and remove the end caps from the air cleaner housing.

Inner Element

Figure 4-3. Removing Elements.

3. After the paper element is removed, check the condition of the inner element. It should be replaced whenever it appears dirty, typically every other time the paper element is replaced or every 600 hours. Clean the area around the base of the inner element before removing it, so dirt does not get into the engine.

4.1

Section 4 Air Cleaner and Air Intake System

4. Do not wash the paper element and inner

element or use compressed air, this will damage the elements. Replace dirty, bent, or damaged elements with new genuine Kohler elements as required. Handle the new elements carefully; do not use if the sealing surfaces are bent or damaged.

5. Check all parts for wear, cracks, or damage, and that ejector area is clean. See Figure 4-4. Replace any damaged components.

Ejector Area

Air Intake/Cooling System

To ensure proper cooling, make sure the grass screen, cooling fan fins, and external surfaces of the engine are kept clean at all times.

Seasonally or every 150 hours of operation (more often under extremely dusty or dirty conditions), remove the cylinder shrouds and blower housing. Clean the cooling fins and external surfaces as necessary. Make sure all shrouds are reinstalled.

Cylinder Shroud

Figure 4-4. Ejector Area.

6. Install the new inner element, followed by the paper element. Slide each fully into place in the air cleaner housing.

7. Reinstall the end caps and secure with the retaining clips. See Figure 4-1.

Air Cleaner Components

Whenever the air cleaner cover is removed, or the paper element or inner element are serviced, check the following:

Air Cleaner Housing - Make sure the housing is not damaged or broken and properly secured.

Air Cleaner Inlet - Make sure the air cleaner inlet is secured tightly to the carburetor and not cracked or damaged.

Breather Tube - Make sure the tube is attached to the air cleaner base and the breather cover.

Figure 4-5. Removing Shrouds for Cleaning.

NOTE: Damaged, worn or loose air cleaner

components can allow unfiltered air into the engine causing premature wear and failure. Tighten or replace all loose or damaged components.

4.2

Fuel System and Governor

Section 5

Fuel System and Governor

Section 5

Description

This section covers the standard carbureted fuel system used on these engines. The governor system used is covered at the end of this section.

WARNING: Explosive Fuel!

Fuel System Components

The typical carbureted fuel system and related components include the following:

• Fuel Tank and Valve

• Fuel Lines

• In-line Fuel Filter

• Fuel Pump

• Carburetor

Operation

The fuel from the tank is moved through the in-line filter and fuel lines by the fuel pump. On engines not equipped with a fuel pump, the fuel tank outlet is located above the carburetor inlet allowing gravity to feed fuel to the carburetor.

Fuel then enters the carburetor float bowl and is drawn into the carburetor body. There, the fuel is mixed with air. This fuel-air mixture is then burned in the engine combustion chamber.

Fuel Recommendations

General Recommendations

Purchase gasoline in small quantities that can be used within 30 days and store only in clean, approved containers. Do not use gasoline left over from the previous season, unless treated with a fuel stabilizer (see Storage in Section 1), to minimize gum deposits and ensure easy starting. Do not use gasoline containing Methanol, or add oil to the gasoline.

Do not overfill the fuel tank. Leave room for the fuel to expand.

Fuel Type

For best results, use only clean, fresh, unleaded gasoline with a pump sticker octane rating of 87 or higher. In countries using the Research fuel rating method, it should be 90 octane minimum.

Unleaded gasoline is recommended as it leaves less combustion chamber deposits and reduces harmful exhaust emissions. Leaded gasoline is not recommended .

Gasoline/Alcohol blends

Gasoline/Ether blends

Methyl Tertiary Butyl Ether (MTBE) and unleaded gasoline blends (up to a maximum of 15% MTBE by volume) are approved as a fuel for Kohler engines. Other gasoline/ether blends are not approved.

Fuel Filter

Most engines are equipped with an in-line fuel filter. Periodically inspect the filter and replace with a genuine Kohler filter seasonally or every 150 operating hours.

Fuel Line

These engines use Low Permeation SAE 30 R7 rated fuel line; certified to meet emission requirements. Standard fuel line may not be used. Order replacement hose by part number through a Kohler Engine Service Dealer.

5.1

Section 5 Fuel System and Governor

Fuel System T ests

When the engine starts hard, or turns over but will not start, it is possible that the problem is in the fuel system. To find out if the fuel system is causing the problem, perform the following tests.

Troubleshooting – Fuel System Related Causes

T e st Conclusion

1. Check the following:

a. Make sure the fuel tank contains clean, fresh,

proper fuel.

b. Make sure the vent in fuel tank cap is open.

c. Make sure the fuel valve is open.

d. Make sure the fuel lines to fuel pump are

secured and in good condition.

2. Check for fuel in the combustion chamber.

a. Disconnect and ground spark plug leads.

b. Close the choke on the carburetor.

c. Crank the engine several times.

d. Remove the spark plug and check for fuel at

the tip.

3. Check for fuel flow from the tank to the fuel pump.

a. Remove the fuel line from the inlet fitting of

the fuel pump.

b. Hold the line below the bottom of the tank.

Open the shut-off valve (if so equipped) and observe flow.

4. Check the operation of the fuel pump.

a. Remove the fuel line from the inlet fitting of

the carburetor.

b. Crank the engine several times and observe

flow.

2. If there is fuel at the tip of the spark plug, fuel is

reaching the combustion chamber.

If there is no fuel at the tip of the spark plug, check for fuel flow from the fuel tank (Test 3).

3. If fuel does flow from the line, check for faulty

fuel pump (Test 4).

If fuel does not flow from the line, check the fuel tank cap vent, fuel pickup screen, in-line filter, shut-off valve, and fuel line. Correct any observed problem and reconnect the line.

4. If fuel does flow from the line, check for faulty

carburetor. (Refer to the Carburetor portions of this section.)

If fuel does not flow from the line, check for a clogged fuel line. If the fuel line is unobstructed, check for overfilled crankcase and/or oil in pulse line. If none of the checks reveal the cause of the problem, replace the pump.

Fuel Pump

General

These engines use either a mechanical fuel pump, or optional remote-mounted electric fuel pump assembly. See Figures 5-1 and 5-2. Operation of the mechanical fuel pump occurs by direct lever/pump actuation off rocker arm movement. The pumping action causes the diaphragm on the inside of the pump to pull fuel in on its downward stroke and to push it into the carburetor on its upward stroke, internal check valves prevent fuel from going backward through the pump.

5.2

Fuel Pump

Figure 5-1. Mechanical Fuel Pump.

Section 5

Fuel System and Governor

Figure 5-2. Optional Electric Fuel Pump.

Fuel Pump - Replacement

Replacing the Mechanical Fuel Pump

The mechanical fuel pump is an integral part of the valve cover assembly and not serviced separately. See Figure 5-1.

1. Disconnect the fuel lines from the inlet and outlet fittings. Note orientation.

Self-Relieving Choke

Figure 5-3. Keihin Two-Barrel Carburetor.

Troubleshooting Checklist

When the engine starts hard, runs roughly, or stalls at low idle speed, check the following areas before adjusting or disassembling the carburetor.

• Make sure the fuel tank is filled with clean, fresh gasoline.

• Make sure the fuel tank cap vent is not blocked and that it is operating properly.

Low Idle Fuel Adjustments (With Limiters)

Slow Jets Bowl Vent

Fuel Shut-Off Solenoid

2. Follow the procedure for replacing the valve cover (see Sections 8 and 10).

3. Reconnect the fuel lines to the inlet and outlet fittings and secure with the clamps.

Carburetor

General

Engines in this series are equipped with a Keihin BK two-barrel, side-draft carburetor with fixed main jets on a matching intake manifold. The carburetor features a self-relieving choke, serviceable slow jets, main jets, bowl drain and a fuel shutdown solenoid. See Figure 5-3.

WARNING: Explosive Fuel

• Make sure fuel is reaching the carburetor. This includes checking the fuel shut-off valve, fuel tank filter screen, in-line fuel filter, fuel lines and fuel pump for restrictions or faulty components as necessary.

• Make sure the air cleaner base and carburetor are securely fastened to the engine using gaskets in good condition.

• Make sure the air cleaner element (including precleaner if equipped) is clean and all air cleaner components are fastened securely.

• Make sure the ignition system, governor system, exhaust system, and throttle and choke controls are operating properly.

If the engine is hard-starting, runs roughly, or stalls at low idle speed, it may be necessary to adjust or service the carburetor.

5.3

Section 5 Fuel System and Governor

Troubleshooting – Carburetor Related Causes

Condition

1. Engine starts hard, runs roughly, or stalls at idle speed.

2. Engine runs rich (indicated by black, sooty exhaust smoke, misfiring, loss of speed and power, governor hunting, or excessive throttle opening).

Possible Cause/Probable Remedy

1. Low idle fuel mixture (some models)/speed improperly adjusted. Adjust the low idle speed tab, then adjust the low idle fuel needle.

2a. Clogged air cleaner. Clean or replace.

b. Choke partially closed during operation. Check the choke lever/

linkage to ensure choke is operating properly.

c. Low idle fuel mixture is improperly adjusted. Adjust low idle

fuel needle (some models).

d. Float level is set too high. Adjust float according to Float

Replacement Procedure.

e. Dirt under the fuel inlet needle. Remove needle; clean needle and

seat and blow with compressed air.

f. Bowl vent or air bleeds plugged. Remove low idle fuel adjusting

needle. Clean vent, ports, and air bleeds. Blow out all passages with compressed air.

g. Leaky, cracked or damaged float. Submerge float to check for

leaks.

3. Engine runs lean (indicated by misfiring, loss of speed and power, governor hunting, or excessive throttle opening).

4. Fuel leaks from carburetor. 4a. Float level set too high. See Remedy 2d.

High Altitude Operation

When operating the engine at altitudes of 1500 m (5000 ft.) and above, the fuel mixture tends to get over-rich. This can cause conditions such as black, sooty exhaust smoke, misfiring, loss of speed and power, poor fuel economy, and poor or slow governor response.

To compensate for the effects of high altitude, special high altitude jet kits are available. The kits include new main jets, slow jets (where applicable), necessary gaskets, and O-Rings. Refer to the parts manual for the correct kit number.

3a. Low idle fuel mixture is improperly adjusted. Adjust low idle

fuel needle (some models).

b. Float level is set too low. Adjust float according to Float

Replacement Procedure.

c. Idle holes plugged; dirt in fuel delivery channels. Remove low

idle fuel adjusting needle. Clean main fuel jet and all passages; blow out with compressed air.

b. Dirt under fuel inlet needle. See Remedy 2e.

c. Bowl vents plugged. Blow out with compressed air.

d. Carburetor bowl gasket leaks. Replace gasket.

Fuel Shut-Off

Solenoid

Fuel Shut-off Solenoid

Most carburetors are equipped with a fuel shut-off solenoid. The solenoid is attached to the fuel bowl. See Figure 5-4. The solenoid has a spring-loaded pin that retracts when 12 volts is applied to the lead, allowing fuel flow to the main jets. When current is removed the pin extends blocking the fuel flow.

5.4

Figure 5-4. Fuel Shut-off Solenoid.

Below is a simple test, made with the engine off, that can determine if the solenoid is functioning properly:

1. Shut off fuel and remove the solenoid from the carburetor. When the solenoid is loosened and removed, gas will leak out of the carburetor.

Section 5

Fuel System and Governor

Have a container ready to catch the fuel.

2. Wipe the tip of the solenoid with a shop towel or blow it off with compressed air, to remove any remaining fuel. Take the solenoid to a location with good ventilation and no fuel vapors present. You will also need a 12 volt power source that can be switched on and off.

3. Be sure the power source is switched off. Connect the positive power source lead to the red lead of the solenoid. Connect the negative power source lead to the solenoid body.

4. Turn the power source on and observe the pin in the center of the solenoid. The pin should retract with the power on and return to its original position with the power off. Test several times to verify operation.

Carburetor Details

The Keihin BK two-barrel carburetor is a side-draft design. The circuits within the carburetor function as described following:

Float Circuit:

The fuel level in the bowl is maintained by the float and fuel inlet needle. The buoyant force of the float stops fuel flow when the engine is at rest. When fuel is being consumed, the float will drop and fuel pressure will push the inlet needle away from the seat, allowing more fuel to enter the bowl. When demand ceases, the buoyant force of the float will again overcome the fuel pressure, rising to the predetermined setting and stop the flow.

Slow & Mid-Range Circuit:

At low speeds the engine operates only on the slow circuit. As a metered amount of air is drawn through the slow air bleed jets, fuel is drawn through the two main jets and further metered through the slow jets. Air and fuel are mixed in the body of the slow jet and exit to the transfer port. From the transfer port the air fuel mixture is delivered to the idle progression chamber. From the idle progression chamber the air fuel mixture is metered through the idle port passages. At low idle when the vacuum signal is weak, the air/fuel mixture is controlled by the setting of the idle fuel adjusting screws. This mixture is then mixed with the main body of air and delivered to the engine. As the throttle plate opening increases, greater amounts of air/fuel mixture are drawn in through the fixed and metered idle progression holes. As the throttle plate opens further the vacuum signal becomes great enough so the main circuit begins to work.

Main (High-Speed) Circuit:

At high speeds/loads the engine operates on the main circuit. As a metered amount of air is drawn through the four air jets, fuel is drawn through the main jets. The air and fuel are mixed in the main nozzles and then enter the main body of airflow, where further mixing of the fuel and air occurs. This mixture is then delivered to the combustion chamber. The carburetor has a fixed main circuit; no adjustment is possible.

Carburetor Adjustments

Adjustment

NOTE: Carburetor adjustments should be made

only after the engine has warmed up.

The carburetor is designed to deliver the correct fuelto-air mixture to the engine under all operating conditions. The main fuel jet is calibrated at the factory and is not adjustable*. The idle fuel adjusting needles are also set at the factory and normally do not need adjustment.

*NOTE: Engines operating at altitudes above

approximately 1500 m (5000 ft.) may require a special high altitude main jet. Refer to High Altitude Operation later in this section.

If, however, the engine is hard-starting or does not operate properly, it may be necessary to adjust or service the carburetor.

Low Idle Speed (RPM) Adjustment

1. Low Idle Speed (RPM) Setting: Place the throttle control in the idle or slow position. Set the low idle speed approximately 300 RPM* less than the intended or specified Governed Idle Speed, by turning the low idle speed adjusting screw in or out. Check the speed using a tachometer.

IMPORTANT: The Governed Idle Speed Adjustment must follow any resetting of the Low Idle Speed.

*NOTE: The actual low idle speed depends on

the application. Refer to the equipment manufacturer’s recommendations. The low idle speed for basic engines is 1200 RPM. To ensure best results when setting the low idle fuel needle, the low idle speed should be 1200 RPM (± 75 RPM).

5.5

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Kohler CH980, CH960, CH1000, CH940 User Manual

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