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.
Section 1
1
NOTE
Note is used to notify people of installation, operation, or maintenance information that is important
but not hazard-related.
For Your 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!
ȱǯȱȱ
ȱȱȱȱ¢ȱȱ
ǯȱBefore working on the engine
or equipment, disable the engine as
follows: 1) Disconnect the spark plug
lead(s). 2) Disconnect negative (-)
baery cable from baery.
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 aer 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
aer it is turned off. Never operate
the engine with heat shields or guards
removed.
WARNING
1.1
Page 6
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
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.
WARNING
Explosive Gas can cause fires and
severe acid burns.
Charge baery only in a well
ventilated area. Keep sources of
ignition away.
Explosive Gas!
Baeries produce explosive hydrogen
gas while being charged. To prevent a
fire or explosion, charge baeries only
in well ventilated areas. Keep
sparks, open flames, and other sources
of ignition away from the baery at all
times. Keep baeries out of the reach
of children. Remove all jewelry when
servicing baeries.
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.
1.2
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.
Page 7
Engine Identification Numbers
When ordering parts, or in any communication
involving an engine, always give the Model, Specification, and Serial Numbers of the engine.
The engine identification numbers appear on a decal
affixed to the engine shrouding. See Figure 1-1. An
explanation of these numbers is shown in Figure 1-2.
Figure 1-2. Explanation of Engine Identification Numbers.
1.3
Page 8
Section 1
Safety and General Information
Oil Recommendations
Using the proper type and weight of oil in the
crankcase is extremely important, as is checking oil
daily and changing oil regularly. 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 SJ or higher. Select
the viscosity based on the air temperature at the time
of operation as shown below.
RECOMMENDED SAE VISCOSITY GRADES
10W-30
**
5W-20, 5W-30
°F -2002032 406080100
°C -30-20-10010203040
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 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.
Figure 1-3. Oil Container Logo.
*
E
S
I
P
A
SAE
10W-30
V
R
I
Kohler 10W-30
C
E
S
J
Refer to Section 6 - Lubrication System for detailed
oil check, oil change, and oil filter change procedures.
Fuel Recommendations
WARNING: 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.
General Recommendations
Purchase gasoline in small quantities and store
in clean, approved containers. A container with a
capacity of 2 gallons or less with a pouring spout is
recommended. Such a container is easier to handle
and helps eliminate spillage during refueling.
Do not use gasoline le over from the previous
season, to minimize gum deposits in your fuel
system and to ensure easy starting.
Do not 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
(R+M)/2 or higher. In countries using the Research
Octane Number (RON), it should be 90 octane
minimum. 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.
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.
1.4
Page 9
Periodic Maintenance
Section 1
Safety and General Information
WARNING: Accidental Starts!
ȱǯȱȱȱȱȱȱ¢ȱȱǯȱBefore working on the engine or equipment,
disable the engine as follows: 1) Disconnect the spark plug lead(s). 2) Disconnect negative (-) baery cable from baery.
Maintenance Schedule
Normal maintenance, replacement or repair of emission control devices and systems may be performed by any
repair establishment or individual; however, warranty repairs must be performed by a Kohler authorized
service center.
Maintenance RequiredFrequency
• Fill fuel tank.
Daily or Before
Starting Engine
Annually
or Every 25 Hours
Annually or
Every 100 Hours
Every 200 Hours
• Check oil level.
• Check air cleaner for dirty¹, loose, or damaged parts.
• Check air intake and cooling areas, clean as necessary¹.
• Service precleaner element¹ (if equipped).
• Service air cleaner element¹ (if not equipped with precleaner).
• Replace air cleaner element¹ (if equipped with precleaner).
• Change oil and filter (more frequently under severe conditions).
• Remove cooling shroud and clean cooling areas.
• Check that all fasteners are in place and components are properly secured.
• Replace fuel filter.
• Check spark plug condition and gap.
• Have valve lash checked/adjusted2.
1
Every 500 Hours
¹Perform these maintenance procedures more frequently under extremely dusty, dirty conditions.
²Have a Kohler Engine Service Dealer perform this service.
Storage
If the engine will be out of service for two months or
more, use the following storage procedure:
1. Clean the exterior surfaces of the engine.
2. Change the oil and oil filter while the engine is
still warm from operation. See Change 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 2-3 minutes to get stabilized fuel into the
carburetor.
• Have bendix starter drive serviced².
• Replace spark plug.
To empty the system, run the engine until the
tank and system are empty.
4. Due to the deep recess around the spark plug,
blow out the cavity with compressed air. Remove
the spark plug. The spark plug is most accessible
when the blower housing is removed for
cleaning.
Add one tablespoon of engine oil into the spark
plug hole. Install the plug, but do not connect
the plug lead. Crank the engine two or three
revolutions. Connect the plug lead.
5. Reinstall the blower housing, if removed
previously, and torque the blower housing screws
to 7.5 N·m (65 in. lb.).
6. Store the engine in a clean, dry place.
1.5
Page 10
Section 1
Safety and General Information
VALVE COVER VIEW
Dimensions in millimeters. Inch equivalents shown in ().
Figure 1-4. Typical Engine Dimensions.
1.6
Page 11
Safety and General Information
General Specifications¹
Power (@ 3600 RPM, exceeds Society of Automotive Engineers-Small Engine Test Code J1940)
Values are in metric units. Values in parentheses are English equivalents. Lubricate threads with engine oil prior
to assembly, EXCEPT for air cleaner base thread forming screw - install dry.
1.7
Page 12
Section 1
Safety and General Information
Closure Plate
Closure Plate Fastener Torque ........................................................................ 24.5 N·m (216 in. lb.)
Balance Weight Guide Channel Width
New .............................................................................................................. 17.95/18.05 mm (0.707/0.711 in.)
Max. Wear Limit ......................................................................................... 18.13 mm (0.714 in.)
Connecting Rod
Cap Fastener Torque (torque in 2 increments).............................................. 5.5, 11.5 N·m (50, 100 in. lb.)
Connecting Rod-to-Crankpin Running Clearance
New ............................................................................................................... 0.03/0.055 mm (0.0012/0.0022 in.)
Max. Wear Limit .......................................................................................... 0.07 mm (0.0025 in.)
Connecting Rod-to-Crankpin Side Clearance ................................................ 0.25/0.59 mm (0.0098/0.0232 in.)
Connecting Rod-to-Piston Pin Running Clearance ....................................... 0.015/0.028 mm (0.0006/0.0011 in.)
Piston Pin End I.D.
New ............................................................................................................... 22.015/22.023 mm (0.8667/0.8670 in.)
Max. Wear Limit .......................................................................................... 22.036 mm (0.8675 in.)
Crankcase
Governor Cross Sha Bore I.D.
New ............................................................................................................... 6.025/6.05 mm (0.2372/0.2382 in.)
Max. Wear Limit .......................................................................................... 6.063 mm (0.2387 in.)
Oil Drain Plug Torque ....................................................................................... 14.0 N·m (125 in. lb.)
Crankshaft
End Play (free) .................................................................................................... 0.225/1.025 mm (0.0089/0.040 in.)
Cranksha Bore in Crankcase I.D.
New .............................................................................................................. 41.965/41.990 mm (1.6521/1.6531 in.)
Max. Wear Limit ......................................................................................... 42.016 mm (1.654 in.)
Cranksha Bore in Closure Plate I.D.
New .............................................................................................................. 44.965/44.990 mm (1.7703/1.7713 in.)
Max. Wear Limit ......................................................................................... 45.016 mm (1.7723 in.)
Flywheel End Main Bearing Journal O.D.
New - Before Serial No. 3703200003 ....................................................... 44.913/44.935 mm (1.7682/1.7691 in.)
New - Aer Serial No. 3703200013 ......................................................... 44.870/44.895 mm (1.7665/1.7675 in.)
O.D. - Max. Wear Limit ............................................................................. 44.84 mm (1.765 in.)
Max. Taper .................................................................................................. 0.0220 mm (0.0009 in.)
Max. Out of Round .................................................................................... 0.025 mm (0.001 in.)
PTO End Main Bearing Journal O.D.
New - Before Serial No. 3703200003 ........................................................ 41.913/41.935 mm (1.6501/1.6510 in.)
New - Aer Serial No. 3703200013 .......................................................... 41.855/41.880 mm (1.6478/1.6488 in.)
O.D. - Max. Wear Limit ............................................................................. 41.83 mm (1.647 in.)
Max. Taper .................................................................................................. 0.020 mm (0.0008 in.)
Max. Out of Round .................................................................................... 0.025 mm (0.001 in.)
1.8
Page 13
Section 1
Safety and General Information
Crankshaft (Continued)
Cranksha Bore in Closure Plate Running Clearance
New - Before Serial No. 3703200003 ........................................................ 0.030/0.077 mm (0.0012/0.0030 in.)
New - Aer Serial No. 3703200013 .......................................................... 0.070/0.120 mm (0.0027/0.0047 in.)
Cranksha Bore in Crankcase Running Clearance
New - Before Serial No. 3703200003 ........................................................ 0.030/0.077 mm (0.0012/0.0030 in.)
New - Aer Serial No. 3703200013 .......................................................... 0.085/0.135 mm (0.0033/0.0053 in.)
Connecting Rod Journal O.D.
New .............................................................................................................. 40.982/41.000 mm (1.6134/1.6141 in.)
Max. Wear Limit ......................................................................................... 40.964 mm (1.612 in.)
Max. Taper .................................................................................................. 0.012 mm (0.0005 in.)
Max. Out of Round .................................................................................... 0.025 mm (0.001 in.)
Cranksha T.I.R.
PTO End, Cranksha in Engine ............................................................... 0.15 mm (0.0059 in.)
Entire Cranksha, in V-Blocks ................................................................. 0.10 mm (0.0039 in.)
Cranksha Eccentrics O.D.
New .............................................................................................................. 66.940/66.970 mm (2.6354/2.6366 in.)
Max. Wear Limit ......................................................................................... 66.89 mm (2.633 in.)
1
Balance Weight
Balance Weight Bearing Surface I.D.
New .............................................................................................................. 67.011/67.086 mm (2.6382/2.6412 in.)
Max. Wear Limit ......................................................................................... 67.140 mm (2.6430 in.)
Balance Weight Pin O.D.
New .............................................................................................................. 11.950/11.975 mm (0.4705/0.4715 in.)
Max. Wear Limit ......................................................................................... 11.900 mm (0.4685 in.)
Guide Shoe Width - Before Serial No. 3618000003
New ............................................................................................................. 17.85/17.90 mm (0.703/0.705 in.)
Max. Wear Limit ......................................................................................... 17.75 mm (0.6988 in.)
Guide Shoe Hole I.D.
New .............................................................................................................. 12.000/12.025 mm (0.4724/0.4734 in.)
Max. Wear Limit ......................................................................................... 12.050 mm (0.4744 in.)
Linkage Pin O.D. (Crankcase) - Aer Serial No. 3618000013
New .............................................................................................................. 11.964/11.975 mm (0.4710/0.4715 in.)
Max. Wear Limit ......................................................................................... 11.900 mm (0.4685 in.)
Balance Weight Linkage- Aer Serial No. 3618000013
New .............................................................................................................. 11.985/12.010 mm (0.4719/0.4728 in.)
Max. Wear Limit ......................................................................................... 12.035 mm (0.4738 in.)
Balance Weight Screw Torque ......................................................................... 10.9-13.2 N·m (95.0-115.0 in. lb.)
1.9
Page 14
Section 1
Safety and General Information
Cylinder Bore
Cylinder Bore I.D.
New
SV470, SV480-00XX .................................................................................. 84.000/84.025 mm (3.307/3.308 in.)
SV470, SV480-01XX .................................................................................. 89.000/89.025 mm (3.504/3.505 in.)
SV530, SV540 ............................................................................................. 89.000/89.025 mm (3.504/3.505 in.)
SV590, SV600, SV610, SV620 ................................................................... 94.010/94.035 mm (3.701/3.702 in.)
Max. Wear Limit
SV470, SV480-00XX .................................................................................. 84.073 mm (3.310 in.)
SV470, SV480-01XX .................................................................................. 84.073 mm (3.310 in.)
SV530, SV540 ............................................................................................. 89.073 mm (3.507 in.)
SV590, SV600, SV610, SV620 ................................................................... 94.073 mm (3.704 in.)
Max. Taper .................................................................................................. 0.05 mm (0.002 in.)
Max. Out of Round .................................................................................... 0.12 mm (0.0047 in.)
Cylinder Head
Cylinder Head Fastener Torque (torque in 2 increments) .......................... 20.5, 41.0 N·m (180, 360 in. lb.)
Max. Out-of-Flatness ........................................................................................ 0.8 mm (0.003 in.)
Rocker Arm Pivot Stud Torque ....................................................................... 13.5 N·m (120 in. lb.)
Rocker Arm Adjustment Nut Set Screw ........................................................ 5.5 N·m (50 in. lb.)
Electric Starter
Thru Bolt Torque ............................................................................................... 3.3-3.9 N·m (30-35 in. lb.)
Mounting Nut Torque ...................................................................................... 3.6 N·m (32 in. lb.)
Nut (Top) Positive (+) Brush Lead Terminal ................................................. 1.6-2.8 N·m (15-25 in. lb.)
Nut (Flange) Positive (+) Brush Lead Terminal ............................................ 2.2-4.5 N·m (20-40 in. lb.)
Ignition Module Air Gap ................................................................................ 0.203/0.305 mm (0.008/0.012 in.)
Ignition Module Fastener Torque ................................................................... 6.0 N·m (55 in. lb.) Into new as-cast hole
4.0 N·m (35 in. lb.) Into used hole
Muffler
Muffler Retaining Nuts Torque ...................................................................... 24.4 N·m (216 in. lb.)
Oil Filter
Oil Filter Torque ................................................................................................ refer to the oil filter for instructions.
Oil Filter Pad Pipe Plug
1/8” N.P.T.F. Torque .......................................................................................... 4.5-5.0 N·m (40-46 in. lb.)
Oil Pump
Mounting Screw Torque .............................................................5.0-7.5 N·m (44.4-66.0 in. lb.) Into new as-cast hole
3.8-4.6 N·m (33.3-40.3 in. lb.) Into used hole
Pump Gears-to-Crankcase Side Clearance .................................................... 0.165/0.315 mm (0.0065/0.0124 in.)
1
Oil Sentry
Pressure Switch Torque .................................................................................... 4.5-5.0 N·m (40-45 in. lb.)
Piston, Piston Rings, and Piston Pin
Piston Pin Bore I.D.
New .............................................................................................................. 22.006/22.012 mm (0.8685/0.8666 in.)
Max. Wear Limit ......................................................................................... 22.025 mm (0.8671 in.)
Piston Pin O.D.
New .............................................................................................................. 21.995/22.0 mm (0.8659/0.8661 in.)
Max. Wear Limit ......................................................................................... 21.994 mm (0.8658 in.)
Top Compression Ring-to-Groove Side Clearance ..................................... 0.04 mm (0.0016 in.)
Middle Compression Ring-to-Groove Side Clearance ............................... 0.04 mm (0.0016 in.)
Top and Middle Compression Ring End Gap
New Bore
Top Ring .................................................................................................... 0.15/0.40 mm (0.006/0.016 in.)
Middle Ring .............................................................................................. 0.30/0.55 mm (0.012/0.022 in.)
Used Bore (max.) ........................................................................................ 0.77 mm (0.030 in.)
Piston Thrust Face O.D.²
SV470, SV480-00XX
New ............................................................................................................ 83.948/83.962 mm (3.3050/3.3056 in.)
Max. Wear Limit ....................................................................................... 83.828 mm (3.3003 in.)
SV470, SV480-01XX
New ............................................................................................................ 88.948/88.962 mm (3.5018/3.5024 in.)
Max. Wear Limit ....................................................................................... 88.828 mm (3.4972 in.)
²Measure 8 mm (0.314 in.) above the boom of the piston skirt at right angles to the piston pin.
1.11
Page 16
Section 1
Safety and General Information
Piston, Piston Rings, and Piston Pin (Continued)
SV530, SV540
New ............................................................................................................ 88.948/88.962 mm (3.5018/3.5024 in.)
Max. Wear Limit ....................................................................................... 88.828 mm (3.4972 in.)
SV590, SV600, SV610, SV620
New ............................................................................................................ 93.928/93.942 mm (3.6980/3.6985 in.)
Max. Wear Limit ....................................................................................... 93.828 mm (3.6940 in.)
2
Piston Thrust Face-to-Cylinder Bore
SV470, SV480, SV530, SV540 .................................................................... 0.045 mm (0.0018 in.)
SV560, SV590, SV600, SV610, SV620 ....................................................... 0.0880 mm (0.0035 in.)
Rectifier-Regulator
Mounting Screw Torque ................................................................................... 6.0 N·m (55 in. lb.) Into new as cast hole
4.0 N·m (35 in. lb.) Into used hole
Speed Control
Speed Control Bracket Assembly Fastener Torque ......................................11.0 N·m (95 in. lb.) Into new as-cast hole
7.5 N·m (65 in. lb.) Into used hole
Stator
Stator Mounting Screw Torque ....................................................................... 6.0 N·m (55 in. lb.) Into new as-cast hole
4.0 N·m (35 in. lb.) Into used hole
Throttle/Choke Controls
Governor Control Lever Fastener Torque ..................................................... 7.0-8.5 N·m (60-75 in. lb.)
Running Clearance
Valve Cover
Valve Cover Fastener Torque........................................................................... 11.0 N·m (95 in. lb.) Into new as-cast hole
7.5 N·m (65 in. lb.) Into used hole
Valves and Valve Lifters
Intake Valve Lash3 ............................................................................................. 0.127 mm (0.005 in.)
Exhaust Valve Lash3 .......................................................................................... 0.178 mm (0.007 in.)
Intake Valve Minimum Li ............................................................................. 8.9 mm (0.350 in.)
Exhaust Valve Minimum Li .......................................................................... 8.9 mm (0.350 in.)
N·m = in. lb. x 0.113
N·m = . lb. x 1.356
in. lb. = N·m x 8.85
. lb. = N·m x 0.737
Noncritical
Fasteners
Into Aluminum
Torque
1.13
Page 18
Section 1
Safety and General Information
1.14
Page 19
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
2
Tools
DescriptionSource/Part No.
Balance Gear Timing Tool (K & M Series)
To hold balance gears in timed position when assembling engine.
Camsha Endplay Plate
For checking camsha endplay.
Camsha Seal Protector (Aegis)
To protect seal during camsha installation.
Cylinder Leakdown Tester
For checking combustion retention and if cylinder, piston, rings, or valves are worn.
Electric Starter Drive Lubricant (Inertia Drive) Kohler 52 357 01-S
Electric Starter Drive Lubricant (Solenoid Shi) Kohler 52 357 02-S
RTV Silicone Sealant
Loctite® 5900 Heavy Body in 4 oz aerosol dispenser.
Only oxime-based, oil resistant RTV sealants, such as those listed, are approved
for use. Loctite® Nos. 5900 or 5910 are recommended for best sealing characteristics.
Loctite® 5910
Loctite® Ultra Black 598
Loctite® Ultra Blue 587
Loctite® Ultra Copper
Spline Drive LubricantKohler 25 357 12-S
Kohler 25 597 07-S
2
2.3
Page 22
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 that 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 li the rocker arms or turn the
cranksha 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/Crankshaft Tool.
2.4
Page 23
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 common types of engine troubles are listed
below. Use these to help locate the possible cause(s).
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 disconnected.
6. Kill switch in off position.
7. Faulty spark plug.
8. Faulty ignition module.
9. Fuel solenoid malfunction.
10. Choke not closing.
11. Baery connected backwards.
12. Safety interlock system engaged.
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 throle 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. Poor fuel, dirt or water in the fuel system.
3. Clogged fuel line.
4. Loose or faulty wires or connections.
5. Faulty or misadjusted choke or throle controls.
6. Faulty spark plug.
7. Low compression.
8. Faulty ACR mechanism.
9. Weak spark.
10. Fuel pump malfunction causing lack of fuel.
Section 3
Troubleshooting
3
11. Engine overheated-cooling/air circulation
restricted.
12. Flywheel key sheared.
13. Intake system leak.
Engine Will Not Crank
1. PTO drive is engaged.
2. Baery 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.
7. Seized internal engine components.
Engine Runs But Misses
1. Dirt or water in the fuel system.
2. Spark plug faulty or fouled.
3. Poor quality of fuel.
4. Spark plug lead boot loose on plug.
5. Loose wires or connections that intermiently
short the kill terminal of ignition module to
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.
Engine Knocks
1. Excessive engine load.
2. Low crankcase oil level.
3. Old or improper fuel.
4. Internal wear or damage.
5. Quality of fuel.
6. 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 plug.
8. Low compression.
9. Exhaust restriction.
10. Low baery.
11. Incorrect governor seing.
Engine Uses Excessive Amount of Oil
1. Incorrect oil viscosity/type.
2. Clogged, broken, or inoperative 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.
• Check for buildup of dirt and debris on the
crankcase, cooling fins, grass screen and other
external surfaces. Dirt or debris on these areas
can cause overheating.
• Check for obvious oil leaks and damaged
components. Excessive oil leakage can indicate
a clogged or inoperative breather, worn or
damaged seals or gaskets, or loose fasteners.
• 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 improper
maintenance.
• Check the carburetor throat for dirt. Dirt in the
throat is further indication that the air cleaner
was not functioning properly.
• Check if the oil level is within the operating range
on the dipstick. If it is above, sniff for gasoline
odor.
• Check the condition of the oil. Drain the oil into
a container; it 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 the wrong type or weight of oil was
used, the oil was not changed at the recommended
intervals, an over-rich fuel mixture, or weak ignition,
to name a few possible causes.
Oil Leaks from Oil Seals, Gaskets
1. Clogged, broken, or inoperative breather.
2. Worn or broken piston rings.
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.
3.2
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
Aer 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.
Page 25
Section 3
Troubleshooting
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.
Basic Engine Tests
Crankcase Vacuum Test
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-operating breather) can cause oil to be
forced out at oil seals, gaskets, or other available spots.
Crankcase vacuum is best measured with a water
manometer or vacuum/pressure test gauge. See
Section 2. Complete instructions are provided with the
testers.
Test the crankcase vacuum with the manometer as
follows:
1. Insert the rubber stopper into the oil fill hole.
Be sure the pinch clamp is installed on the
hose and use the tapered adapters to connect
the hose between the stopper and one of the
manometer tubes. Leave the other tube open to
the atmosphere. Check that the water level in the
manometer is at the “0” line. Make sure the pinch
clamp is closed.
2. Start the engine and run at no-load high idle
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 the same as the
open side (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 pinch clamp before stopping the
engine.
To perform the test with the vacuum/pressure gauge:
1. Insert the stopper as in step 1.
2. Insert the barbed gauge fiing into the hole in the
stopper. Be sure the gauge needle is at “0”.
3. Run the engine, as in step 2, and observe the
gauge reading. Needle movement to the le
of “0” is a vacuum, and movement to the right
indicates a pressure. A minimum of 10.2 cm (4 in.)
of vacuum should be present.
3
Incorrect Vacuum in Crankcase
Possible CauseSolution
1. Crankcase breather clogged or inoperative.
2. Seals and/or gaskets leaking. Loose or
improperly torqued fasteners.
3. Piston blowby or leaky valves. Confirm with
cylinder leakdown test.
4. Restricted exhaust.
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.
compression release (ACR) mechanism. Because
of the ACR mechanism, it is difficult to obtain an
accurate compression reading. As an alternate, use the
leakdown test described below.
Cylinder Leakdown Test
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 is a relatively simple,
inexpensive leakdown tester for small engines.
The tester includes a quick disconnect coupling for
aaching the adapter hose and a holding tool.
Leakdown Test Instructions
1. Run the engine for 3-5 minutes to warm it up.
2. Remove the spark plug.
3. Rotate the cranksha until the piston is at top
dead center of the compression stroke. You
will need to hold the engine in this position
while testing. The holding tool supplied with
the tester can be used if the PTO end of the
cranksha is accessible. Slide the holding tool
onto the cranksha, align the slot with one of the
mounting holes on the PTO face, and tighten it
onto the cranksha. Install a 3/8" breaker bar into
the slot of the holding tool, so it is perpendicular
to both the holding tool and cranksha, or insert
a shoulder bolt through the slot and thread it into
the mounting hole. If the flywheel end is more
accessible, you can use a breaker bar and socket
on the flywheel nut/screw to hold it in position.
You may need an assistant to hold the breaker
bar during testing. If the engine is mounted in
a piece of equipment, you may be able 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 aach it to the tester at this time.
5. Connect an adequate air source (80-100 psi) to the
tester.
6. Turn the regulator knob in the increase
(clockwise) direction until the gauge needle is in
the yellow set area at the low (right) end of the
scale.
7. Connect the tester quick-disconnect to the
adapter. Note the gauge reading and listen for
escaping air at the carburetor inlet, exhaust
outlet, and/or crankcase breather.
8. Check your test results against the table below:
Leakdown Test Results
Air escaping from crankcase breather ................................................Defective rings or worn cylinder walls.
Air escaping from exhaust system ......................................................Defective exhaust valve.
Air escaping from carburetor ...............................................................Defective intake valve.
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
Page 27
Air Cleaner and Air Intake System
Section 4
Air Cleaner and Air Intake System
Section 4
Air Cleaner
These engines are equipped with a replaceable, high
density, paper air cleaner element. Some engines also
have an oiled, foam precleaner, located in the outer air
cleaner cover. See Figure 4-1.
Air Cleaner
Base
Optional Foam Precleaner
Intake air is drawn in through the upper opening from
the blower housing, passes through the precleaner
(if so equipped), the paper element and then into
the carburetor. The outer air cleaner cover is secured
by two knobs, and removed by turning the knobs
counterclockwise.
Air Cleaner Element
Air Cleaner Cover
4
Figure 4-1. Air Cleaner Assembly - Exploded View.
Check the air cleaner daily or before starting the
engine. Check for and correct any buildup of dirt and
debris, and loose or damaged components.
NOTE: Operating the engine with loose or
damaged air cleaner components could
allow unfiltered air into the engine causing
premature wear and failure.
Air
Cleaner
Cover
Knobs
Precleaner Service
If so equipped, wash and oil the precleaner annually
or every 25 hours of operation (more oen under
extremely dusty or dirty conditions).
1. Loosen the air cleaner cover knobs and remove
the cover.
2. Remove the precleaner.
4.1
Page 28
Section 4
Air Cleaner and Air Intake System
3. Wash the precleaner in warm water with
detergent. Rinse the precleaner thoroughly until
all traces of detergent are eliminated. Squeeze out
excess water (do not wring). Allow the precleaner
to air dry.
4. Saturate the precleaner with new engine oil.
Squeeze out all excess oil.
5. Reinstall the precleaner into the outer cover.
6. Install the air cleaner cover and secure with the
two knobs.
7. When precleaner replacement is necessary, order
Kohler Part No. 20 083 03-S.
Paper Element Service
Check the paper element annually or every 25 hours
of operation (more oen under extremely dusty or
dirty conditions). Clean or replace the element as
necessary. Replace the air cleaner element annually or every 100 hours.
1. Remove the air cleaner cover and the precleaner
(if so equipped), service as required.
2. Remove the air cleaner element with the integral
rubber seal.
8. When element replacement is necessary, order
Kohler Part No. 20 083 02-S.
Inspect Air Cleaner Components
Whenever the air cleaner cover is removed, or the
paper element or precleaner is serviced, check the
following areas/components:
Outer Air Cleaner Cover - Make sure the air cleaner
cover is in good condition, not cracked, damaged, or
missing a retaining knob, which can affect the sealing
ability of the air cleaner element.
Air Cleaner Base - Make sure the base is properly
secured and not cracked or damaged. Since the
air cleaner base and carburetor are secured to the
intake port with common hardware, it is extremely
important that the fasteners securing these
components are tight at all times. The air cleaner
base also provides the mounting points for the air
cleaner cover retaining studs. Make sure the bosses
are not cracked, broken or damaged, and the studs are
properly secured.
Before reinstalling an air cleaner base that has been
removed, make sure the metal bushings in the base
mounting holes are present. See Figure 4-2. The
bushings prevent damage to the base and maintain
the proper mounting torque.
3. Gently tap the pleated side of the paper element
to dislodge dirt. Do not wash the paper element
or use pressurized air, as this will damage the
element. Replace a dirty, bent, or damaged
element with a genuine Kohler element. Handle
new elements carefully; do not use if the rubber
seal is damaged.
4. Clean all air cleaner components of any
accumulated dirt or foreign material. Prevent any
dirt from entering the throat of the carburetor.
5. Install the air cleaner element with the pleated
side out and seat the rubber seal onto the edges
of the air cleaner base.
6. Reinstall the precleaner (if so equipped), into
the upper section of the air cleaner cover. Make
sure the hole in the precleaner is aligned with the
upper mounting knob. See Figure 4-1.
7. Reinstall the air cleaner cover and secure with the
two knobs.
Figure 4-2. Bushings in Air Cleaner Base.
Breather Hose - Make sure the hose is not cracked or
damaged, and aached to both the air cleaner base
and valve cover.
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
Page 29
Figure 4-3. Breather Hose.
Disassembly
The following procedure is for complete disassembly
of all air cleaner components. As the removal of the
air cleaner base also affects carburetor mounting and
governor adjustment, steps 3 and 4 should only be
performed if required. Detailed photos are provided
in Sections 5, 8, and 10 for the various individual
steps.
Section 4
Air Cleaner and Air Intake System
Reassembly
The following procedure is for complete assembly of
all air cleaner components. Steps 1-3 are necessary
only if the air cleaner base and/or the cover mounting
studs were removed in Section 8, Disassembly.
1. Install the mounting studs into the air cleaner
base if removed previously. Tighten the studs
until boomed, or to the end of threads (do not
force).
2. Install the air cleaner base gasket and air cleaner
base, with the two metal spacers, onto the
mounting stud(s) and/or alignment pin. Make
sure the upper mounting tab is located above the
closure plate. Install and finger tighten the hex
flange nut(s). When a long M6 thread forming
mounting screw is used, apply hand pressure
to keep the parts from shiing, then remove the
alignment pin and install the M6 thread forming
screw. DO NOT OIL. Torque the nut(s) to
5.5 N·m (48 in. lb.). Torque the screw to 8.0 N·m
(70 in. lb.) into a new hole, or 5.5 N·m (48 in. lb.)
into a used hole, do not over tighten.
4
1. Loosen the air cleaner cover retaining knobs and
remove the air cleaner cover.
2. Remove the foam precleaner (if so equipped),
and the air cleaner element with formed rubber
seal.
3. Disconnect the breather hose from the valve
cover or air cleaner base.
NOTE: The air cleaner base should be removed
only if necessary.
4. Remove the two hex flange nuts from the
mounting studs. If one stud and one thread
forming screw is used; first remove the thread
forming screw on the right side of the carburetor
inlet, which secures the air cleaner base,
carburetor and gaskets. Insert a 3/16” diameter
rod approximately 4” long, into the hole to serve
as a temporary alignment pin. Be careful not
to force the rod or damage the threads. Then
remove the hex flange nut from the stud on
the le side of the carburetor inlet. Carefully
remove the air cleaner base and gasket. The cover
mounting studs thread into the air cleaner base,
and they should only be removed if necessary.
3. Reconnect the breather hose and perform the
governor adjustment (Section 5, Initial Governor
Adjustment).
4. Install the air cleaner element with the pleated
side out and seat the rubber seal onto the edges
of the air cleaner base.
5. Install the serviced precleaner (if so equipped)
into the air cleaner cover. Make sure the hole
in the precleaner is aligned with the upper
mounting knob.
6. Reinstall the air cleaner cover and secure with the
two knobs.
4.3
Page 30
Section 4
Air Cleaner and Air Intake System
Air Intake/Cooling System
Clean Air Intake/Cooling Areas
To ensure proper cooling, make sure the grass screen,
cooling fins, and other external surfaces of the engine
are kept clean at all times.
Annually or every 100 hours of operation, (more oen
under extremely dusty, dirty conditions), remove the
blower housing and any other cooling shrouds. Clean
the cooling fins and external surfaces as necessary.
Make sure all parts are reinstalled. Torque the M6
blower housing fasteners to 7.7 N·m (68.3 in. lb.).
NOTE: Operating the engine with a blocked grass
screen, dirty or plugged cooling fins, and/or
cooling shrouds removed, will cause engine
damage due to overheating.
4.4
Page 31
Fuel System and Governor
Section 5
Fuel System and Governor
Section 5
Fuel Recommendations
WARNING: 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.
General Recommendations
Purchase gasoline in small quantities and store
in clean, approved containers. A container with a
capacity of 2 gallons or less with a pouring spout is
recommended. Such a container is easier to handle
and helps eliminate spillage during refueling.
• Do not use gasoline le over from the previous
season, to minimize gum deposits in your fuel
system and to ensure easy starting.
• Do not add oil to the gasoline.
• Do not overfill the fuel tank. Leave room for the
fuel to expand.
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 System
The typical fuel system and related components
include the fuel tank, in-line fuel filter, fuel pump,
carburetor, and fuel lines. Some applications use
gravity feed without a fuel pump.
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 and gravity moves
the fuel.
Fuel then enters the carburetor float bowl and is
moved into the carburetor body. There, the fuel is
mixed with air. This fuel-air mixture is then burned in
the engine combustion chamber.
Troubleshooting
Use the following procedure to check if fuel is
reaching the combustion chamber.
5
Fuel Type
For best results use only clean, fresh, unleaded
gasoline with a pump sticker octane rating of 87
(R+M)/2 or higher. In countries using the Research
Octane Number (RON), it should be 90 octane
minimum. 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.
5.1
Page 32
Section 5
Fuel System and Governor
Fuel System Troubleshooting Guide
TestConclusion
1. Check for the following:
a. Make sure the fuel tank contains clean, fresh,
proper fuel.
b. Make sure the vent in fuel cap is open.
c. Make sure the fuel valve is open.
2. Check for fuel in the combustion chamber.
a. Disconnect and ground spark plug lead.
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 fiing of
the fuel pump.
b. Hold the line below the boom of the tank.
Open the shutoff valve (if so equipped) and
observe flow.
4. Check the operation of fuel pump.
a. Remove the fuel line from the inlet fiing 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, reconnect line and
check for faulty fuel pump (Test 4).
If fuel does not flow from the line, check for
clogged fuel tank vent, fuel pickup screen, shutoff
valve, and fuel lines.
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
clogged fuel line. If the fuel line is unobstructed,
the fuel pump is faulty and must be replaced.
Fuel Filter
Some engines are equipped with an in-line fuel filter.
Periodically inspect the filter and replace when dirty.
Replacement is recommended annually or every 100 hours. Use a genuine Kohler filter.
Fuel Line
These engines use low permeation rated fuel lines,
certified to comply with California and U.S. EPA
evaporative emission requirements. Fuel lines that do
not meet these requirements may not be used. Order
replacement hose through a Kohler Service Center.
Fuel Pump
Some engines are equipped with an optional pulse
fuel pump. See Figure 5-1.
Operation
The fuel pump has two internal chambers separated
by a diaphragm. The air chamber is connected to the
engine crankcase by a rubber hose. The fuel chamber
has an inlet from the fuel tank, and an outlet to the
carburetor. The inlet and outlet each have an internal,
one-way check valve.
Alternating negative and positive pressures in the
crankcase activate the pump. When the piston moves
upward in the cylinder, negative pressure (vacuum)
is created in the crankcase and in the air chamber of
the pump. The diaphragm flexes toward the negative
pressure, and the suction draws fuel past the inlet
check valve, into the fuel chamber. Downward
movement of the piston causes a positive pressure
in the crankcase and air chamber, pushing the
diaphragm in the opposite direction, puing pressure
on the fuel. The inlet check valve has now closed, so
the fuel is forced past the outlet check valve, to the
carburetor.
Repair
Pulse fuel pumps are not serviceable and must be
replaced when faulty.
Removal
1. Disconnect the inlet, outlet, and pulse lines
from the fuel pump. Mark the lines for proper
reassembly.
2. Remove the hex flange screws aaching the fuel
pump.
5.2
Page 33
Installation
1. Install the new fuel pump, and secure with the
hex flange screws. Torque the hex flange screws
to 5.9 N·m (52 in. lb.). Do not over tighten.
2. Connect the inlet, outlet, and pulse lines to their
respective fiings on pump. Secure with the
clamps. See Figure 5-1.
Section 5
Fuel System and Governor
WARNING: 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.
Troubleshooting – Fuel System
If engine troubles are experienced that appear to be
fuel system related, check the following areas before
adjusting or disassembling the carburetor.
Figure 5-1. Pulse Fuel Pump.
Carburetor
These engines are equipped with a Walbro fixed main
jet carburetor. See Figure 5-2. The carburetors will
have a low idle speed adjustment screw, and either
fixed idle, or a limiter cap on the idle fuel adjustment
needle.
• Make sure the fuel tank is filled with clean, fresh
gasoline.
• Make sure the fuel cap vent is not blocked and
that it is operating properly.
• 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 (as equipped), for restrictions or faulty
components.
• 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 is clean, and all
air cleaner components are fastened securely.
• Make sure the ignition system, governor system,
exhaust system, and throle and choke controls
are operating properly.
If, aer checking the items listed above, starting
problems or conditions similar to those listed in the
following table exist, it may be necessary to adjust or
service the carburetor.
5
Figure 5-2. Carburetor.
5.3
Page 34
Section 5
Fuel System and Governor
Troubleshooting – Fuel System
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
throle opening).
3. Engine runs lean. (Indicated by
misfiring, loss of speed and power,
governor hunting, or excessive
throle opening).
4. Fuel leaks from carburetor. 4a. Float level set too high. See Remedy 2c.
1a. Low idle fuel mixture/speed improperly adjusted. Adjust the low
idle speed screw, then adjust the low idle fuel needle.
b. Improper choke adjustment.
2a. Choke partially closed during operation. Check the choke lever/
linkage to ensure choke is operating properly.
b. Low idle fuel mixture is improperly adjusted. Adjust low idle
fuel needle.
c. Float level is set too high. With fuel bowl removed and carburetor
inverted, the exposed surface of float must be parallel with the
bowl gasket surface of the carburetor body.
d. Dirt under fuel inlet needle. Remove needle; clean needle and
seat and blow with compressed air.
e. Bowl vent or air bleeds plugged. Remove fuel bowl, low idle
fuel adjusting needle, and welch plugs. Clean vent, ports, and air
bleeds. Blow out all passages with compressed air.
f. Fuel bowl gasket leaks. Remove fuel bowl and replace gasket.
g. Leaky, cracked, or damaged float. Submerge float to check for
fuel needle.
b. Float level is set too low. With fuel bowl removed and carburetor
inverted, the exposed surface of float must be parallel with the
bowl gasket surface of the carburetor body.
c. Idle holes plugged; dirt in fuel delivery channels. Remove fuel
bowl, low idle fuel adjusting needle, and welch plugs. Clean
main fuel jet and all passages; blow out with compressed air.
b. Dirt under fuel inlet needle. See Remedy 2d.
c. Bowl vent plugged. Remove fuel bowl and clean bowl vent. Blow
out with compressed air.
d. Float is cracked or damaged. Replace float.
e. Bowl retaining screw gasket damaged. Replace gasket.
f. Bowl retaining screw loose. Torque screw to specifications.
Possible Cause/Probable Remedy
Carburetor Adjustment
NOTE: Carburetor adjustments should be made only
aer the engine has warmed up.
The carburetor is designed to deliver the correct
fuel-to-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 adjustment
needle is also set at the factory and normally does not
need adjustment. If the engine is hard starting or does
not operate properly, however, it may be necessary to
adjust or service the carburetor.
5.4
Idle Speed (RPM)
Adjustment Screw
Idle Fuel
Mixture Needle
Figure 5-3. Fixed Main Jet Carburetor.
Page 35
Section 5
Fuel System and Governor
Low Idle Mixture Adjustment*
NOTE: Engines will have fixed idle (no adjustment
possible) or a limiter cap on the idle fuel
adjustment needle. Step 2 can only be
performed within the limits allowed by the
cap.
1. Start the engine and run at half throle for 5 to 10
minutes to warm up. The engine must be warm
before doing step 2.
2. Low Idle Fuel Needle Seing: Place the throle
into the idle or slow position.
Turn the low idle fuel adjustment needle out
(counterclockwise) from the preliminary seing
until engine speed decreases (rich). Note the
position of the needle.
Now turn the adjusting needle in (clockwise).
The engine speed may increase, then it will
decrease as the needle is turned in (lean). Note
the position of the needle.
Set the adjusting needle midway between the rich
and lean seings. See Figure 5-4.
Low Idle Speed Setting
1. Start the engine and run at half throle for 5 to 10
minutes to warm up. The engine must be warm
before doing step 2.
2. Low Idle Speed Seing: Place the throle
control into the idle orslow position. Set the
low idle speed by turning the low idle speed
adjusting screw in or out. Check the speed using
a tachometer.
NOTE: The actual low idle speed depends on
the application–refer to equipment
manufacturer’s recommendations. The
recommended low idle speed for basic
engines is 1500 RPM. To ensure best results
when seing the low idle fuel needle, the
low idle speed must not exceed 1500 RPM
(±75 RPM).
5
Lean
Adjust to Midpoint
Rich
Figure 5-4. Optimum Low Idle Fuel Setting.
*NOTE: If the engine is equipped with a governed idle
adjustment (See Figure 5-23), the governor
will compensate for speed changes due to the
low idle mixture adjustment. Disable the
governed idle control by backing out the
governed idle adjusting screw and seing a
fixed idle speed using the idle speed screw
on the carburetor. Make the low idle mixture
adjustment and then reset the governed idle
speed at the adjusting screw.
5.5
Page 36
Section 5
Fuel System and Governor
Disassembly
Throttle Lever and Shaft
Dust Seal
Throttle Plate Screw(s)
Throttle Plate
Low Idle Speed Adjusting
Screw and Spring
Low Idle Fuel Adjusting
Needle and Spring with
Limiter Cap
Choke Lever and Shaft
Choke Return Spring
Choke Plate
Fuel Inlet
Needle
Float
Float Shaft
Bowl Gasket
Fuel Bowl
Fuel Shut-off Solenoid
Figure 5-5. Carburetor - Exploded View.
1. Remove the bowl retaining screw or fuel shut-off
solenoid, retaining screw gasket, and fuel bowl.
2. Remove the bowl gasket, float sha, float, and
fuel inlet needle.
3. Do not aempt to remove the low idle fuel
adjustment needle if it has a limiter cap.
Further disassembly to remove the welch plugs,
main fuel jet, throle plate and sha, and choke
plate and sha is recommended only if these
parts are to be cleaned or replaced.
5.6
Bowl Retaining Screw Gasket
or
Welch Plug Removal
In order to clean the idle ports and bowl vent
thoroughly, remove the welch plugs covering these
areas.
Use SPX Tool No. KO-1018 and the following
procedure to remove the welch plugs. See Figure 5-6.
1. Pierce the welch plug with the tip of the tool.
NOTE: To prevent damage to the carburetor, do
not allow the tool to strike the carburetor
body.
2. Pry out the welch plug with the tip of the tool.
Bowl Retaining Screw
Page 37
Tool No. KO1018
Section 5
Fuel System and Governor
2. The choke plate is inserted into a slot in the
choke sha. Grasp the choke plate with pliers,
and pull it out of the slot. See Figure 5-8.
Do Not Allow
Tip to Strike
Carburetor Body
Figure 5-6. Removing Welch Plug.
Main Fuel Jet Removal
The main jet is pressed into the side of the tower
portion of the body. Removal is not recommended,
unless a high-altitude kit is being installed, in which
case the removal instructions will be included in the
kit.
Fuel Inlet Seat Removal
The fuel inlet seat is pressed into the carburetor body,
do not aempt to remove it. If necessary, clean it in
place with aerosol carburetor cleaner.
Choke Shaft Removal
1. Because the edges of the choke plate are beveled,
mark the choke plate and carburetor body, to
ensure correct reassembly. See Figure 5-7.
Also note the choke plate position in the bore,
and the position of the choke lever and choke
return spring.
Pierce Plug with Tip
Pry Out Plug
Welch Plug
Figure 5-8. Removing Choke Plate.
5
3. Remove the choke sha and choke return spring.
Throttle Shaft Removal
Do not aempt to remove the throle sha, as repair
kits are not available. Throle sha wear is normally
accompanied by corresponding wear to the carburetor
body, making it impractical to aempt a cost-effective
repair. Replace the entire carburetor if the throle
sha is worn.
Cleaning
WARNING: 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.
Figure 5-7. Marking Choke Plate and Carburetor
Body.
All parts should be cleaned thoroughly using a
commercial carburetor cleaner. Make sure all gum
deposits are removed from the following areas.
• Carburetor body and bore; especially the areas
where the throle plate, choke plate and shas
are seated.
• Idle fuel and idle ports in carburetor bore, main
jet, bowl vent, and fuel inlet needle and seat.
• Float and float hinge.
• Fuel bowl.
5.7
Page 38
Section 5
Fuel System and Governor
• Throle plate, choke plate, throle sha, and
choke sha.
NOTE: Do not submerge the carburetor in
cleaner or solvent when plastic, fiber,
rubber, foam seals or gaskets are
installed. The cleaner may damage these
components.
Inspection
Carefully inspect all components and replace those
that are worn or damaged.
• Inspect the carburetor body for cracks, holes, and
other wear or damage.
• Inspect the float for cracks, holes, and missing or
damaged float tabs. Check the float hinge and pin
for wear or damage.
• Inspect the fuel inlet needle and seat for wear or
damage.
• Inspect the tip of the low idle fuel adjustment
needle for wear or grooves.
• Inspect the throle and choke sha and plate
assemblies for wear or excessive play.
Repair
Always use new gaskets when servicing or
reinstalling carburetors. Repair kits are available
which include new gaskets and other components.
Always refer to the Parts Manual for the engine being
serviced to ensure the correct repair kits are ordered.
Reassembly
Choke Shaft Installation
1. Install the choke return spring to the choke sha.
Welch Plug Installation
Use SPX Tool No. KO1017 and install new plugs as
follows:
1. Position the carburetor body with the welch plug
cavities to the top.
2. Place a new welch plug into the cavity with the
raised surface up.
3. Use the end of the tool that is about the same size
as the plug and flaen the plug. Do not force the
plug below the surface of the cavity. See Figure
5-9.
Tool No. KO1017
Carburetor Body
Figure 5-9. Installing Welch Plugs.
4. Aer the plugs are installed, seal them with
Glyptal™ (or an equivalent sealant). Allow the
sealant to dry.
NOTE: If a commercial sealant is not available,
fingernail polish can be used.
Carburetor Reassembly
1. Install the low idle speed adjusting screw and
spring.
New Welch Plug
2. Insert the choke sha with the return spring into
the carburetor body.
3. Rotate the choke lever approximately 1/2 turn
counterclockwise. Make sure the choke return
spring hooks on the carburetor body.
4. Position the choke plate as marked during
disassembly. Insert the choke plate into the slot
in the choke sha. Make sure the choke sha is
locked between the tabs on the choke plate.
5.8
2. If the low idle fuel adjusting needle contains
a limiter, adjust to the midpoint within the
adjustment range.
3. Insert the fuel inlet needle into the float. Align the
needle with the seat and lower the float into the
carburetor body. See Figure 5-10. Install the float
sha.
Page 39
Section 5
Fuel System and Governor
Figure 5-10. Installing Float and Fuel Inlet Needle.
4. Install the bowl gasket, fuel bowl, bowl retaining
screw gasket, and bowl retaining screw or fuel
solenoid.
Torque the bowl retaining screw to 5.1-6.2 N·m
(45-55 in. lb.).
Fuel Shut-off Solenoid
Many engines are equipped with a fuel shut-off
solenoid installed in place of the bowl retaining screw
to eliminate backfiring when the engine is shut down.
If backfiring occurs on engines equipped with this
solenoid, verify that the correct shutdown procedure
is being used. In order for the solenoid to be effective,
the engine must be running between half and full throle when the key is turned off. Next, check the
baery to ensure that it is not discharged or faulty. A
minimum of 7.3 volts DC is required to activate the
solenoid. Also check to see that the ground lead from
the carburetor body to the air cleaner base mounting
screw is properly connected.
Figure 5-11. Fuel Shut-Off Solenoid.
High Altitude Operation
Operating the engine with the wrong engine
configuration at a given altitude may increase
its emissions and decrease fuel efficiency and
performance. To ensure correct engine operation
at altitudes above 1219 meters (4000 ), it may be
necessary to have an authorized Kohler dealer install
a special high altitude jet kit in the carburetor. If a
high altitude kit has been installed, the engine must
be reconverted to the original jet size, before it is
operated at lower altitudes, or overheating and engine
damage can result.
To obtain high altitude kit information or locate a
dealer near you, call 1-800-544-2444 to find the names
of the nearest Kohler Co. Service Centers or, access
our web site at: www.kohlerengines.com and click on
the “Service & Dealer Locator” located in the upper
right hand corner. The service center will need your
engine specification number which is found on your
Engine ID Label.
5
If these check out, the solenoid should be removed for
bench testing. Remember to shut off the fuel supply
and catch any fuel spilling from the carburetor as the
solenoid is removed.
Bench test the solenoid by grounding the solenoid
case and applying 12 volt DC to the spade terminal. If
the plunger does not retract, the solenoid is faulty and
must be replaced. Always use a new fuel bowl gasket
whenever the solenoid is installed. Refer to the wiring
diagram in Section 7 and connect the fuel shut-off
solenoid.
Unitized Throttle and Choke Control
Some engines are equipped with a unitized throle
and choke control. This assembly controls the choke
and engine speed with a single lever. See Figure 5-12.
5.9
Page 40
Section 5
Fuel System and Governor
Throttle Cable Adjustment
1. Loosen the control cable clamp. See Figure 5-12.
Cable
Clamp
Figure 5-12. Speed Control Bracket with Unitized
Throttle/Choke Control.
2. Place the throle control lever of the equipment
into the fast or high speed position. The actuating
tab+ of the choke lever should be just below the
end of the choke adjusting screw. See Figure 5-13.
Choke
Adjustment
Screw
Cold Engine
Figure 5-14. Typical Throttle/Choke Controls.
3. Early Models: Early models use a single
alignment hole to set the engine RPM. Align
the hole in the throle lever with the hole in the
speed control bracket by inserting a pencil or 6.35
mm (1/4 in.) drill bit. See Figure 5-15.
Alignment Hole
Figure 5-15. Alignment Hole in Speed Control
Bracket and Throttle Lever. (Early Models)
throle control slightly past the fast
position. If the throle control does not
have a designated choke on position, be
sure to leave sufficient throle control
travel past the fast position. This will
enable the choke to be placed on. See
Figure 5-14.
5.10
Later Models: Later models use a new control
assembly, identified by two opposing alignment
holes (close to the throle lever pivot), instead of
one. Based upon the intended high-speed (RPM)
seing, throle cable adjustment must be made
by matching the hole in the control lever with the
correct alignment hole. Use the lower (le side)
hole for high-speed seings above 3000 RPM. Use
the upper (right side) hole for high-speed seings
lower than 3000 RPM. Move the throle lever to
align the hole in the lever with the correct hole in
the control bracket. Insert a pencil or a 6.35 mm
(1/4 in.) drill bit to hold in position. See Figure
5-16.
Page 41
Section 5
Fuel System and Governor
4. Pull on the outer shield of the throle control
cable to remove any slack. Tighten the cable
clamp securely.
Alignment Hole
Alignment Hole
for 3000 RPM
and Higher
Figure 5-16. Alignment Holes in Speed Control
Bracket and Throttle Lever. (Later Models)
Starting an Engine Equipped with Unitized Throttle
and Choke Control
1. For a Cold or Warm Engine – Place the throle/
choke control into the fast/choke on position.
This will also place the choke into the on
position. See Figure 5-17.
for Less Than
3000 RPM
NOTE: If the engine develops sufficient speed
to disengage the starter but does not
keep running (a false start), engine
rotation must be allowed to come to
a complete stop before aempting
to restart the engine. If the starter is
engaged while the flywheel is rotating,
the starter pinion and flywheel ring gear
may clash, resulting in damage to the
starter.
If the starter does not turn the engine over, shut the
starter off immediately. Do not make further aempts
to start the engine until the condition is corrected. Do
not jump start using another baery (refer to Baery,
Section 7). See your Kohler Engine Service Dealer for
trouble analysis.
5
4. For Operation – Aer the engine starts, move
the throle/choke control from the fast/choke on position and set the desired engine operating
speed (between the slow and fast position).
High Speed (RPM) Adjustment
The recommended maximum no-load high speed
(RPM) for most engines is 3300 RPM. The actual high
speed (RPM) depends on the application. Refer to the
equipment manufacturer’s instructions for specific
information.
Figure 5-17. Throttle Position for Starting Engine.
2. Make sure the equipment is in neutral.
3. Activate the starter switch. Release the switch as
soon as the engine starts.
NOTE: Do not crank the engine continuously
for more than 10 seconds at a time.
If the engine does not start, allow a
60 second cool down period between
starting aempts. Failure to follow
these guidelines can burn out the starter
motor.
WARNING: Overspeed is Hazardous!
Do not tamper with the governor seing. Over speed is
hazardous and could cause personal injury.
1. Make sure the throle cable is adjusted properly
(see ‘Throle Cable Adjustment).
2. Start the engine and allow it to warm up. Place
the throle control lever into the fast or high
speed position. Turn the choke adjustment
screw (see Figure 5-13) out/counterclockwise, so
there is clearance from the choke lever, and that
contact cannot occur during Step 4. See Figure
5-13.
3. Early Models: Early models use a single
alignment hole to set the engine RPM. Align
the hole in the throle lever with the hole in the
speed control bracket by inserting a pencil or 6.35
mm (1/4 in.) drill bit. See Figure 5-15.
5.11
Page 42
Section 5
Fuel System and Governor
Later Models: Later models utilize a new design
control assembly, identified by two opposing
alignment holes (close to the throle lever pivot),
instead of one. Based upon the intended high
speed (RPM) seing, throle cable adjustment
must be made matching the hole in the control
lever with the appropriate alignment hole. Use
the lower (le side) hole for high-speed seings
3000 RPM and above. Use the upper (right side)
hole for high-speed seings less than 3000 RPM.
Move the throle lever to align the hole in the
lever with the appropriate hole in the control
bracket. Insert a pencil or a 6.35 mm (1/4 in) drill
bit to hold in position. See Figure 5-16.
4. Loosen the speed control bracket mounting
screws. Slide the bracket forward or backward,
until the desired high speed (RPM) is reached.
See Figure 5-18. Check the speed with a
tachometer.
Choke Adjustment
This procedure must follow the High Speed
Adjustment just described. If not already completed,
perform that operation first.
1. Turn the choke adjusting screw out
(counterclockwise), until it no longer contacts the
choke lever.
2. Then turn it back in (clockwise), until it just
makes contact.
3. While observing the choke link, move the throle
control lever to the low idle (slow) position, then
back to full throle (fast). The choke link should
not move as the throle moves through the
normal range. If it does, back the adjusting screw
out until it no longer moves.
4. Move the throle control lever to the choke
position. Check if the choke has fully closed by
placing your finger on the right side of the lower
end of the choke lever/choke link and applying
gentle pressure towards the carburetor. If the
controls have been properly set, the link should
not move.
Figure 5-18. Adjusting High Speed (RPM).
To increase the high speed (RPM), move the
bracket toward the carburetor.
To decrease the high speed (RPM), move the
bracket away from the carburetor.
5. Tighten the speed control bracket mounting
screws. Recheck the speed with a tachometer and
readjust if necessary.
Torque the mounting screws as follows:
Into new as-cast hole – 11.0 N·m (95 in. lb.).Into used hole – 7.5 N·m (65 in. lb.).
6. Adjust the choke (see Choke Adjustment which
follows).
Separate Throttle and Choke Control
Some engines are equipped with separate throle and
choke controls. This allows you to adjust the choke
and throle controls individually.
Install Separate Control Cables
Throttle Control Installation
1. Loosen the two cable clamp screws on the speed
control bracket assembly. See Figure 5-19.
2. Move the application throle control lever to the
maximum full (fast) throle position, and then
move it back 3/16" or 4.75 mm. Insert the cable
boden wire into the throle control lever on the
control plate.
3. Position the throle cable under the cable clamp.
5.12
Page 43
Choke
Cable Clamp
Section 5
Fuel System and Governor
5. Pull on the outer shield of the throle control
cable to remove any slack. Tighten the cable
clamp securely.
Throttle
Cable Clamp
Figure 5-19. Separate Choke and Throttle Cable
Controls.
4. Early Models: Early models use a single
alignment hole to set the engine RPM. Align
the hole in the throle lever with the hole in the
speed control bracket by inserting a pencil or 6.35
mm (1/4 in.) drill bit. See Figure 5-20.
Alignment Hole
Alignment Hole
Alignment Hole
for 3000 RPM
and Higher
Figure 5-21. Alignment Holes in Speed Control
Bracket and Throttle Lever. (Later Models)
6. Move the application throle lever to the slow
position, then to full throle. Check the engine
control to ensure it stops against the stop screw,
which means it is properly set.
Choke Control Installation
1. Connect the choke cable boden wire to the engine
choke control lever on the speed control bracket
assembly.
2. Position the choke cable under the cable clamp.
3. Push/move the choke control to the off position
in the application panel until it booms, then pull
it back approximately 1/16 in.
for Less Than
3000 RPM
5
Figure 5-20. Alignment Hole in Speed Control
Bracket and Throttle Lever. (Early Models)
Later Models: Later models utilize a new design
control assembly, identified by two opposing
alignment holes (close to the throle lever pivot),
instead of one. Based upon the intended high
speed (RPM) seing, throle cable adjustment
must be made matching the hole in the control
lever with the appropriate alignment hole. Use
the lower (le side) hole for high-speed seings
3000 RPM and above. Use the upper (right side)
hole for high-speed seings less than 3000 RPM.
Move the throle lever to align the hole in the
lever with the appropriate hole in the control
bracket. Insert a pencil or a 6.35 mm (1/4 in.) drill
bit to hold in position. See Figure 5-21.
4. Push on the choke cable, ahead of the clamp on
the engine control plate, until the choke lever
stops. Do not force. Then tighten the cable clamp
screw.
5. Move the choke control until it stops (on
position). Check that the choke link cannot be
moved towards the carburetor by applying finger
pressure on the lower link/lever below the engine
control plate. If the choke link moves, readjust by
following steps 3 and 4.
6. Push/move the choke control in/down until it
booms. The choke lever and link should be to
the right at the end of its travel, with linkage free
so the engine does not run on partial choke.
5.13
Page 44
Section 5
Fuel System and Governor
Starting an Engine Equipped with Separate
Control Cables
1. Place the throle control midway between the
slow and fast positions. Place the choke control
into the on position.
2. Start the engine.
3. For a Cold Engine – Gradually return the choke
control to the off position aer the engine starts
and warms up.
The engine/equipment may be operated during
the warm up period, but it may be necessary
to leave the choke partially on until the engine
warms up.
4. For a Warm Engine – Return choke to off position
as soon as engine starts.
Changing the High Speed (RPM) on the Engines
with Separate Controls (Increase or Decrease
RPM)
1. Check that the governor spring and installation
matches the intended high speed RPM operating
range. Refer to Figure 5-27 or 5-28.
4. To ensure that the RPM has been obtained, move
the throle lever to low idle/slow then back to
full throle/fast position and check the RPM with
a tachometer.
Setting the Low Idle RPM
1. Move the application control to slow position.
2. Using a tachometer, check the RPM. Then, using
a screwdriver, turn the low idle speed screw (see
Figure 5-3) inward (clockwise) to increase the
RPM, and outward (counterclockwise) to lower
the RPM.
Governed Idle Adjustment
A governed idle control system was supplied as
a option on early engines and is standard on later
model engines. The purpose of this system is to
maintain a desired idle speed regardless of ambient
conditions (temperature, parasitic load, etc.) that may
change. The later models can be identified by the two
opposing alignment holes, (adjacent from the throle
lever pivot) rather than one. Based upon the intended
high speed (RPM) seing, cable adjustment must be
made matching the hole in the control lever with the
appropriate alignment hole.
2. Start the engine, move the application throle
lever to full throle/fast, and loosen the mounting
screws of the main speed control bracket to allow
repositioning. See Figure 5-22.
Figure 5-22. Adjusting High Speed (RPM).
3. To increase the RPM: Move the speed control
bracket, towards the carburetor. To decrease the RPM: Move the speed control bracket, away from
the carburetor. Check the RPM with a tachometer
and tighten screws when correct seing has been
obtained. See Figure 5-19.
The system requires an additional procedure for
seing the idle speed. If speed adjustments are
required proceed as follows.
1. Make any necessary speed or control adjustments
following the appropriate instructions already
covered in this section.
2. Move the throle control to the idle position.
Hold the governor lever away from the
carburetor, so the throle lever is tight against the
idle speed adjusting screw. Check the speed with
a tachometer and adjust it to 1500-1750 RPM.
3. Release the governor lever and allow the engine
to return to the governed idle speed. Check
it with a tachometer against the equipment
manufacturers recommended idle speed. If
adjustment is necessary, use the governed idle
adjusting screw on the speed control assembly
(see Figure 5-23). Turn the screw clockwise
to increase the governed idle speed and
counterclockwise to decrease it.
5.14
Page 45
Governed Idle
Adjusting Screw
Figure 5-23. Location of Governed Idle Adjusting
Screw.
Governor
These engines are equipped with a centrifugal
flyweight mechanical governor, designed to hold
the engine speed constant under changing load
conditions. The governor gear/flyweight mechanism is
mounted on the closure plate in the crankcase, and is
driven off a gear on the cranksha.
NOTE: Flyweights must be installed perpendicular
to the nylon gear as shown. Improper
installation of the flyweights may cause
damage to the governor gear. See Figure 5-24.
Section 5
Fuel System and Governor
The governor lever is clamped on the protruding end
of the sha and connected with linkage to the throle
lever on the carburetor, so any rotation of the sha
causes corresponding movement of the throle plate.
When the engine is at rest, and the throle is in the
fast position, the tension of the governor spring holds
the throle plate open. When the engine is operating
(the governor gear assembly is rotating), the force
applied by the regulating pin against the cross sha
tends to close the throle plate. The governor spring
tension and the force applied by the regulating pin are
in equilibrium during operation, holding the engine
speed constant.
When load is applied and the engine speed (and
governor gear speed) decreases, the governor spring
tension moves the governor arm to open the throle
plate wider. This allows more fuel into the engine;
increasing engine speed. This action takes place very
rapidly, so a reduction in speed is hardly noticed. As
the speed reaches the governed seing, the governor
spring tension and the force applied by the regulating
pin will again be in equilibrium. This maintains the
engine speed at a relatively constant level.
The governed speed seing is determined by the
position of the throle control. It can be variable or
constant, depending on the application.
5
Flyweights
Nylon Gear
Figure 5-24. Governor Gear/Flyweight Assembly.
Operation
As the governor gear rotates, centrifugal force causes
the flyweights to move outward as speed increases.
As the flyweights move outward, they cause the
regulating pin to move outward.
The regulating pin contacts the tab on the cross sha,
causing the sha to rotate. One end of the cross sha
protrudes through the side of the crankcase.
Initial Adjustment
Make this initial adjustment whenever the governor
arm is loosened or removed from the cross sha. To
ensure proper seing, make sure the throle linkage
is connected to the governor arm and the throle lever
on the carburetor. See Figures 5-25 and 5-26.
1. Move the governor lever toward the carburetor
(wide open throle). Do not apply excess force
flexing or distorting the throle link.
2. Grasp the cross sha with pliers, and turn the
sha counterclockwise as far as it will go, then
tighten the hex nut. Torque the hex nut to
7.0-8.5 N·m (60-75 in. lb.).
5.15
Page 46
Section 5
Fuel System and Governor
Figure 5-25. Governor Adjustment.
Governor Sensitivity Adjustment
Governor sensitivity is adjusted by repositioning the governor spring in the holes in the governor lever. If speed
surging occurs with a change in load, the governor is set too sensitive. If a big drop in speed occurs when a
normal load is applied, the governor should be set for greater sensitivity.
The desired high speed seing (RPM) will determine the governor spring position in the governor lever and the
throle lever, as well as the spring used. See Figure 5-27 and 5-28.
Throttle
Lever
1
2
3
Governor
Lever
1
2
3
Figure 5-26. Tightening Governor Lever Nut.
Single
Alignment
Hole
High Speed
RPM
;
;
;
Figure 5-27. Early Style Governor Spring Location Chart.
5.16
Governed
Idle RPM
Governed
Lever Hole No.
Throttle Lever
Hole No.
White
Spring
Green
Spring
Black
Spring
Page 47
Section 5
Fuel System and Governor
Single
Hole
2
1
2
Throttle
Lever
/HVVWKDQ5306LQJOH+ROH;%
/HVVWKDQ5306LQJOH+ROH;$
Figure 5-28. Later Style Governor Spring Location Chart.
3
Governor
Lever
(Single Hole)
High Speed
RPM
Governed
Idle RPM
Governor
Lever
(Multiple Hole)
Governed
Lever Hole No.
3
1
Alignment Hole
for 3000 RPM
and Higher
Throttle Lever
Hole No.
A
Red
Spring
B
Alignment Hole
for Less Than
3000 RPM
Alignment
Hole
5
5.17
Page 48
Section 5
Fuel System and Governor
5.18
Page 49
Section 6
Lubrication System
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. 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 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
*
Section 6
Lubrication System
V
R
I
C
E
S
I
P
A
SAE
10W-30
Figure 6-2. Oil Container Logo.
Check Oil Level
The importance of checking and maintaining
the proper oil level in the crankcase cannot be
overemphasized. Check oil BEFORE EACH USE as
follows:
E
S
J
6
Kohler 10W-30
°F -2002032 406080100
°C -30-20-10010203040
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)
Figure 6-1. Viscosity Grades Table.
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 6-2.
1. Make sure the engine is stopped, level, and is
cool so the oil has had time to drain into the
sump.
2. To keep dirt, grass clippings, etc., out of the
engine, clean the area around the oil fill cap/
dipstick before removing it.
3. Remove the oil fill cap/dipstick; wipe oil off. See
Figure 6-3. Reinsert the dipstick into the tube and
fully seat the dipstick in the tube. See Figure 6-4.
Figure 6-3. Removing Dipstick.
6.1
Page 50
Section 6
Lubrication System
Oil Filter
Oil Drain Plug
Figure 6-4. Dipstick Seated.
4. Remove the dipstick and check the oil level. The
oil level should be up to, but not over the ‘‘F’’
mark on the dipstick. See Figure 6-5.
Operating
Range
Figure 6-5. Oil Level Dipstick.
5. If the level is low, add oil of the proper type, up
to the ‘‘F’’ mark on the dipstick. Always check the
level with the dipstick before adding more oil.
NOTE: To prevent extensive engine wear or
damage, always maintain the proper oil
level in the crankcase. Never operate
the engine with the oil level below the
‘‘L’’ mark or over the ‘‘F’’ mark on the
dipstick.
Change Oil and Oil Filter
Change the oil and oil filter annually or every 100
hours of operation. Change the oil and oil filter while
the engine is still warm. The oil will flow more freely
and carry away more impurities. Make sure the
engine is level when filling or checking oil. Change
the oil and filter as follows (see Figure 6-6). Always use a genuine Kohler oil filter.
Figure 6-6. Oil Drain Plug, Oil Filter.
1. To keep dirt, grass clipping, etc., out of the
engine, clean the area around the oil fill cap/
dipstick before removing it.
2. Remove the drain plug and oil fill cap/dipstick.
Be sure to allow ample time for complete
drainage.
3. Remove the old filter and wipe off the mounting
pad.
4. Reinstall the oil drain plug and torque to 14 N·m (125 in. lb.).
5. Place the new replacement filter in a shallow pan
with the open end up. Pour new oil of the proper
type, in through the threaded center hole. Stop
pouring when the oil reaches the boom of the
threads. Allow a minute or two for the oil to be
absorbed by the filter material.
6. Apply a thin film of clean oil to the rubber gasket
on the new filter.
7. Install the new oil filter to the filter adapter or oil
cooler. Refer to instructions on the oil filter for
proper installation.
8. Fill the crankcase with new oil of the proper type,
to the “F” mark on the dipstick.
9. Reinstall the oil fill cap/dipstick and push firmly
into place.
10. Test run the engine to check for leaks. Stop the
engine, allow a minute for the oil to drain down,
and recheck the level on the dipstick. Add more
oil, as necessary, so the oil level is up to but not
over the “F” mark.
6.2
Page 51
Section 6
Lubrication System
NOTE: To prevent extensive engine wear or
damage, always maintain the proper oil
level in the crankcase. Never operate
the engine with the oil level below the
‘‘L’’ mark or over the ‘‘F’’ mark on the
dipstick.
Full-Pressure Lubrication System
Operation
This engine uses a full-pressure lubrication system
to deliver oil for internal lubrication. A cam driven,
high efficiency Gerotor™ oil pump located in the
crankcase maintains proper oil flow and oil pressure
even at low speeds and high operating temperatures.
Oil is supplied from the pump via two circuits to the
cranksha main bearings, cranksha, connecting
rod bearing surfaces, cam gears, and axis shas. An
integral pressure relief valve within the oil pump
limits the maximum pressure of the system.
For a cold engine at start up, the oil pressure can
go up to 20-25 psi. For a warm (normal operating
temperature) engine at idle speed, the oil pressure can
go down to 5 psi.
Service
The oil pump rotors typically require no servicing, if
normal maintenance is performed as outlined in
Section 1.
The closure plate must be removed for access to the
oil pump and the rotors. Refer to the Disassembly
and Reassembly, Sections (8 and 10), for removal and
reinstallation procedures.
Oil Filter
These engines are equipped with a full-flow oil filter.
See Figure 6-8.
The oil filter helps remove sludge and other
combustion by-products from the oil. It also extends
the oil change interval and cools the oil.
Oil Filter
Figure 6-8. Oil Filter Location.
Oil Sentry™
Some engines are equipped with an optional Oil
Sentry™ switch. This switch is designed to prevent
the engine from starting in a low oil or no oil
condition. The Oil Sentry™ may not shut down
a running engine before damage occurs. In some
applications this switch may activate a warning signal.
Read your equipment manuals for more information.
Operation
The pressure switch is designed to break contact
as the oil pressure increases and make contact as
the oil pressure decreases. At oil pressure above
approximately 2 to 5 psi, the switch contacts open.
At oil pressures below approximately 2 to 5 psi, the
switch contacts close.
6
Figure 6-7. Oil Pump on Intake Cam Shaft
(Gerotors Removed from Pump Housing).
On vehicular applications (lawn tractors, mowers,
etc.), the pressure switch can be used to activate a
low oil warning light. On stationary or unaended
applications, the pressure switch can be used to
ground the ignition module to stop the engine.
NOTE: Oil Sentry™ is not a substitute for checking
the oil level BEFORE EACH USE. Make sure
the oil level is maintained up to the ‘‘F’’ mark
on the dipstick. See Figure 6-5.
6.3
Page 52
Section 6
Lubrication System
Installation
The pressure switch is installed into the center oil
galley of the filter adapter casting on the closure plate.
Based on the application an elbow adapter may also
be used. See Figure 6-9. On engines not equipped with
1. Remove and discard the pipe plug from the
center passage of oil filter mounting pad.
2. Apply pipe sealant with Teflon® (Loctite® No.
59241 or equivalent) to the threads of the 90°
adapter (if used), and the Oil Sentry™ switch.
1. Connect the continuity tester across the blade
terminal and the metal case of the switch. With
0 psi pressure applied to the switch, the tester
should indicate continuity (switch closed).
2. Gradually increase the pressure to the switch. The
tester should indicate a change to no continuity (switch open) as the pressure increases through
the range of 2.0/5.0 psi.
The switch should remain open as the pressure is
increased to 90 psi maximum.
3. Gradually decrease the pressure to the switch.
The tester should indicate a change to continuity (switch closed) as the pressure decreases through
the range of 2.0/5.0 psi; approaching 0 psi.
If the switch does not operate as specified,
replace the switch.
Testing Oil Pressure
On some models the engine oil pressure can be tested
using an oil pressure tester. Follow the instructions
included with the tester. The pressure can be tested by
removing the oil filter and installing the tester adapter
on the mounting pad, or by removing the Oil Sentry
pressure switch (or pipe plug) and threading the tester
hose directly into the mounting hole. See Figure 6-10.
™
3. Install the adapter (if used), and carefully tighten
it to the intended position. Do not over tighten or
damage the adapter.
4. Install the switch into the adapter or center
passage. Torque the switch to 4.5-5.0 N·m (40-45 in. lb.).
5. Connect the lead to the terminal on the Oil
Sentry™ switch.
Testing the Oil Sentry™ Switch
The Oil Sentry™ pressure monitor is a normally closed
switch. It is calibrated to open (break contact) with
increasing pressure and close (make contact) with
decreasing pressure within the range of 2.0/5.0 psi.
Compressed air, a pressure regulator, pressure gauge,
and a continuity tester are required to test the switch.
6.4
Locations
For Tester
Figure 6-10. Tester Locations (Some Models).
Page 53
Section 7
Electrical System and Components
Section 7
Electrical System and Components
This section covers the operation, service, and repair of the electrical system and electrical system components.
Major electrical systems and components covered in this section include the ignition system, baery, baery
charging systems, electric starter, and optional Oil Sentry™ oil level pressure switch.
WARNING: Electrical Shock
Never touch electrical wires or components while the engine is running. They can be sources of electrical shock.
Spark Plug
Engine misfire or starting problems are oen caused
by a spark plug that is in poor condition or has an
improper gap seing.
The engine is equipped with the following spark plug:
Type: Champion® RC12YC or QC12YC (RFI Compliant)
Gap 0.76 mm (0.030 in.)
Thread Size: 14 mm
Reach: 19.1 mm (3/4 in.)
Hex Size: 15.9 mm (5/8 in.)
Spark Plug Service
Annually or every 100 hours of operation, remove
the spark plug. Check its condition, and reset the gap
or replace with a new plug as necessary. Spark plug
replacement is recommended at 500 hours.
1. Before removing the spark plug, clean the area
around the base of the plug to keep dirt and
debris out of the engine. Due to the deep recess
around the spark plug, blowing out the cavity
with compressed air is usually the most effective
method for cleaning. The spark plug is most
accessible when the blower housing is removed
for cleaning.
2. Remove the plug and check its condition. Replace
the plug if worn or reuse is questionable.
NOTE: Do not clean the spark plug in a machine
using abrasive grit. Some grit could
remain in the spark plug and enter the
engine, causing extensive wear and
damage.
3. Check the gap using a wire feeler gauge.
Adjust the gap by carefully bending the ground
electrode. Gap plugs to 0.76 mm (0.030 in.). See
Figure 7-1.
Wire Gauge
Spark Plug
0.76 mm
Ground
Electrode
Figure 7-1. Servicing Spark Plug.
4. Reinstall the spark plug into the cylinder head.
Torque the spark plug to 24-30 N·m (18-22 . lb.).
5. Reconnect the spark plug lead and reinstall the
blower housing, if removed previously. Torque the
blower housing screws to 7.7 N·m (68.3 in. lb.).
(0.030 in. )
Gap
7
7.1
Page 54
Section 7
Electrical System and Components
Inspection
Inspect the spark plug as soon as it is removed from
the cylinder head. The deposits on the tip are an
indication of the general condition of the piston rings,
valves, and carburetor.
Normal and fouled plugs are shown in the following
photos.
Chalky White Deposits: Chalky white colored
deposits indicate overheating. This condition is
usually accompanied by excessive gap erosion. A
clogged grass screen, clogged cooling fins, and lean
carburetion are some causes of overheating.
Normal: A plug taken from an engine operating under
normal conditions will have light tan or gray colored
deposits. If the center electrode is not worn, a plug in
this condition could be regapped and reused.
Worn: On a worn plug, the center electrode will be
rounded and the gap will be eroded .010" or more
than the correct gap. Replace a worn spark plug
immediately.
Carbon Fouled: So, sooty, black deposits indicate
incomplete combustion. Incomplete combustion
is usually caused by over-rich carburetion, weak
ignition, or poor compression.
7.2
Wet Fouled: A wet plug is caused by excess fuel, or
oil in the combustion chamber. Excess fuel could be
caused by operating the engine with too much choke
or a dirty air filter. Oil in the combustion chamber is
usually caused by worn piston rings or valve guides.
Page 55
Electronic CD Ignition System
Air Gap
0.203/0.305 mm
(0.008-0.012 in.)
Electrical System and Components
Ignition Module
Spark Plug Boot
Spark Plug
Section 7
Spark Plug
Terminal (C)
Flywheel
Kill Switch or Off
Position of Key Switch
Figure 7-2. Electronic CD Ignition System.
These engines are equipped with a dependable
electronic, capacitive discharge (CD) ignition system.
The system consists of the following components:
• A magnet assembly which is permanently affixed
to the flywheel.
• An electronic, capacitive discharge ignition
module which mounts on the engine crankcase.
Magnet
Lamination (A)
• A spark plug.
• A kill switch (or key switch), which grounds the
module to stop the engine.
Kill Terminal (B)
7
7.3
Page 56
Section 7
Electrical System and Components
D1
SCS
L1
L2
Figure 7-3. Capacitive Discharge Ignition Module.
Operation
As the flywheel rotates, and the magnet passes the
ignition module, the magnetic field induces current
in the input coil (L1). The current pulse is rectified
by a diode (D1) and charges a high-voltage capacitor
(C1). As the magnet completes its pass, it induces
current in a small triggering coil (L2), which turns
on the semiconductor switch (SCS). With the switch
on, the charged capacitor is directly connected to the
primary winding (P) of the transformer (T1). As the
capacitor discharges through the primary, the current
initiates a fast-rising flux field in the transformer core.
The flux field induces a high voltage in the secondary
winding (S) of the transformer. The high voltage pulse
is delivered to the spark plug, where it arcs across the
electrode gap and ignites the fuel-air mixture in the
combustion chamber.
Troubleshooting and Testing CD Ignition
Systems
The CD ignition system is designed to be trouble
free for the life of the engine. Other than periodically
checking/replacing the spark plug, no maintenance
or timing adjustment is necessary or possible. The
ignition module automatically controls the timing
of the spark. Mechanical systems do occasionally
fail or break down, however, so the following
troubleshooting information is provided to help
systematically determine the cause of a reported
problem.
Reported ignition problems are most oen due to
poor or loose connections. Before beginning the test
procedure check all external wiring, including ground
leads for wiring harness and rectifier-regulator (if so
equipped). Be certain all ignition-related wires are
connected, including the spark plug lead, and all
terminal connections fit snugly. Make sure the ignition
switch is in the run position.
C1
NOTE: The CD ignition systems are sensitive to
Preliminary Test
To be certain the reported problem is in the engine
ignition system, it should be isolated from the unit, as
follows.
1. Locate the plug connectors where the wiring
a. If the problem is gone, the electrical system
b. If the problem persists, continue with the
T1
Spark
Plug
P
excessive load on the kill lead. Customer
complaints of hard starting, low power, or
misfire under load may be due to excessive
draw on the kill circuit. Disconnect any
auxiliary kill wires or safety switches
connected to the kill circuit and operate the
engine to determine if the reported problem
is gone.
harnesses from the engine and unit are joined.
Separate the connectors and separate the white
kill lead from the engine connector. Rejoin the
connectors and position or insulate the kill
lead terminal, so it cannot touch ground. Try to
start the engine to verify whether the reported
problem is still present.
on the unit is suspect. Check the key switch,
wires, connections, safety interlocks, etc.
following troubleshooting procedure. Leave
the kill lead isolated until all testing is
completed.
1. Make sure the spark plug lead is connected
to the spark plug.
Engine
Will
Not
Start
2. Check the condition of spark plug. Make
sure gap is set to 0.76 mm (0.030 in.).
3. a. Test for spark with ignition tester (See
Section 2).
Disconnect spark plug lead and connect it to
the post terminal of the tester. See Figure 7-4.
Connect the clip to a good ground, not the
spark plug.
NOTE: To maintain engine speeds normally
obtained during cranking, do not remove the engine spark plug.
b. Make sure the engine ignition switch,
kill switch, or key switch is in the ‘‘run’’
position.
c. Crank the engine (minimum speed 500
RPM), and observe the tester. Visible and
audible sparks should be produced.
2. If plug is in good condition, check/adjust
gap and reinstall.
3. If visible and audible sparks are produced,
the ignition module is OK.
If visible and audible sparks are not
produced:
a. Make sure the engine ignition switch,
b. Check wires and terminals of ignition
c. If wires and terminals are OK, the
Section 7
Conclusion
kill switch, or key switch is in the
‘‘run’’ position.
module and other components for
accidental grounding and damaged
insulation.
ignition module is probably faulty
and should be replaced. Test module
further using an ohmmeter (Test 4).
4. Measure the resistance of module
secondary using an ohmmeter (see Figures
7-2 and 7-5):
Zero ohmmeter before testing. Connect
one ohmmeter lead to laminations (A).
Connect the other lead to the spark plug
terminal (C) of high-tension lead. With the
ohmmeter leads connected in this manner,
the resistance of secondary should be 7,900 to 18,400 ohms.
NOTE: This test cannot be performed
unless module has been fired at
least once.
4. If the resistance is low or 0 ohms, the
module secondary is shorted. Replace the
module.*
If the resistance is high or infinity ohms,
the module secondary is open. Replace the
module.*
If the resistance is within the specified
range, the module secondary is OK.
*Refer to the Disassembly and Reassembly
Sections for complete ignition module
removal and installation procedures.
7
Figure 7-4. Ignition Tester (See Section 2).
Figure 7-5. Testing CD Ignition Module Secondary.
7.5
Page 58
Section 7
Electrical System and Components
Battery
A 12 volt baery with a minimum current rating
of 250 cold cranking amps is recommended. The
actual cold cranking amp requirement depends on
engine size, application and starting temperatures.
As temperatures decrease, cranking requirements
increase but baery capacity shrinks. Refer to the
operating instructions of the equipment this engine
powers for specific baery requirements.
If the baery charge is not sufficient to crank the
engine, recharge the baery. Do not jump start using
another baery.
Battery Charging
WARNING: Explosive Gases!
Baeries produce explosive hydrogen gas while being
charged. To prevent a fire or explosion, charge baeries only
in well ventilated areas. Keep sparks, open flames, and other
sources of ignition away from the baery at all times. Keep
baeries out of the reach of children. Remove all jewelry
when servicing baeries.
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.
Battery Maintenance
Regular maintenance will ensure the baery will
accept and hold a charge.
1. Regularly check the level of electrolyte. Add
distilled water as necessary to maintain the
recommended level.
Battery Test
Test the baery voltage by connecting a DC voltmeter
across the baery terminals and cranking the engine.
If the baery drops below 9 volts while cranking, the
baery is discharged or faulty. Refer to Figure 7-6.
DC
Voltmeter
Battery
Figure 7-6. Checking Battery Voltage.
Electrical Systems Wiring Diagrams and
Battery Charging Systems
Most engines are equipped with either a 9 or 15 amp,
regulated baery charging system. Some have a 3
amp, regulated system with a 70 wa lighting circuit.
Refer to the following wiring diagrams and
troubleshooting guides to test and service the system.
NOTE: Observe the following guidelines to
prevent damage to the electrical system and
components.
1. Make sure the baery polarity is correct. A
negative (-) ground system is used.
NOTE: Do not overfill the baery. Poor
performance or early failure due to loss
of electrolyte will result.
2. Keep the cables, terminals, and external surfaces
of the baery clean. A build-up of corrosive
acid or grime on the external surfaces can selfdischarge the baery. Self-discharging happens
rapidly when moisture is present.
3. Wash the cables, terminals, and external surfaces
with a baking soda and water solution. Rinse
thoroughly with clear water.
NOTE: Do not allow the baking soda solution to
enter the cells of the baery, as this will
destroy the electrolyte.
7.6
2. Disconnect the baery cables (negative (-) cable
first), before doing electric welding on the
equipment powered by the engine.
3. Prevent the stator leads from touching or
shorting while the engine is running. This could
damage the stator.
2. Disconnect the braking lead (green) from
the wiring harness.
With engine running in the fast seing,
measure voltage from braking lead to
ground using an AC voltmeter.
3. With the engine stopped, measure the
resistance from braking lead to ground
using an ohmmeter.
Test
1. Replace burned out lights.
2. If voltage is 35 volts or more, stator
is OK. Circuitry on unit that grounds
braking lead is shorted.
If voltage is less than 35 volts, test stator
using an ohmmeter (Test 3).
3. If resistance is approximately
0.2-0.4 ohms, stator is OK.
If resistance is 0 ohms, stator is shorted.
Replace stator.
If resistance is infinity ohms, stator or
lighting lead is open. Replace stator.
Conclusion
7.10
Page 63
Battery Charging System 9 or 15 amp
Section 7
Electrical System and Components
Ground-to-Kill Lead
A
R
M
Key Switch
Optional
Fuse
_
Battery
+
Starter Solenoid
White
S
B
Engine
Connector
Optional Oil Sentry™
Indicator Light
AC
AC
Violet
Green
B+
RectifierRegulator
Green
Stator
Flywheel
Ignition
Module
Spark
Plug
Red
Optional
Fuel
Solenoid
Optional Oil Sentry™
Switch (Shutdown)
7
Optional Oil Sentry™
Bendix Starter
Switch (Indicator)
Figure 7-9. Regulated Battery Charging System, 9 or 15 amp.
7.11
Page 64
Section 7
Electrical System and Components
Rectifier-Regulator
AC
AC
Figure 7-10. 9 or 15 amp Stator and Rectifier-Regulator.
DC Volt Meter
(-)
B+
9 or 15 Amp Stator
Rectifier-Regulator
AC
B+
AC
Flywheel Stator
Battery
Figure 7-11. Proper Connection to Test 9 or 15 amp Charging System.
7.12
Ammeter
Page 65
Section 7
Electrical System and Components
Troubleshooting Guide 9 or 15 amp Regulated Battery Charging System
NOTE: Zero ohmmeters on each scale to ensure accurate readings. Voltage tests should be made with engine
running at full throle - no load. The baery must be fully charged.
ProblemTestConclusion
1. If voltage is 13.8-14.7 and charge rate increases
when load is applied, the charging system is
OK and baery was fully charged.
If voltage is less than 13.8 or charge rate does
not increase when load is applied, test stator
(Tests 2 and 3).
2. If voltage is 28 volts or more, stator is OK.
Rectifier-regulator is probably faulty. Verify
with Rectifier-regulator tester KO3221.
If voltage is less than 28 volts, stator is probably
faulty and should be replaced. Test stator
further using an ohmmeter (Test 3).
3a. If resistance is 0.1/0.2 ohms, the stator is OK.
If the resistance is infinity ohms, stator is open.
Replace stator.
No
Charge
To
Battery
1. Trace B+ lead from rectifier-regulator to
key switch, or other accessible connection.
Disconnect it from switch or connection.
Connect an ammeter from loose end of B+
lead to positive terminal of baery. Connect
DC voltmeter from loose end of B+ lead to
negative terminal of baery. See Figure 7-11.
With engine running in the fast position, read
voltage on voltmeter.
If voltage is 13.8 volts or more, place a
minimum load of 5 amps* on baery to
reduce voltage. Observe ammeter.
*NOTE: Turn on lights, if 60 was or more.
Or place a 2.5 ohm, 100 wa resistor
across baery terminals.
2. Remove connector from rectifier-regulator.
With engine running in the fast position,
measure AC voltage across stator leads using
an AC voltmeter.
3a. With engine stopped, measure the resistance
across stator leads using an ohmmeter.
7
Battery
Continuously
Charges At
High Rate
3b. With the engine stopped, measure the
resistance from each stator lead to ground
using an ohmmeter.
1. Perform same test as step 1 above.
3b. If the resistance is infinity ohms (no continuity),
the stator is OK (not shorted to ground).
If resistance (or continuity) is measured, the
stator is shorted to ground. Replace stator.
1. If the voltage is 14.7 volts or less the charging
system is OK. The baery is unable to hold a
charge. Service baery or replace as necessary.
If voltage is more than 14.7 volts, the
rectifier-regulator is faulty. Replace
rectifier-regulator.
7.13
Page 66
Section 7
Electrical System and Components
Blade Stop Stator Brake Circuit
The blade stop stator brake circuit is provided as a safety feature to ensure the application can meet ANSI
(American National Standards Institute) application blade stop requirements.
The circuit is activated if the operator gets o of the seat of the application while mower blade system is activated
or in certain reverse mow conditions.
The circuit is activated by taking the ignition shutdown (kill) lead to ground. This action turns on the stator-brake
relay which shorts the charging AC stator leads to produce a magnetic eld that will counter or resist the rotation
of the ywheel. This added resistance to rotation decreases the amount of time it takes for the application deck
blades to come to a full stop.
As the Kohler blade stop stator brake circuit oen is operated in conjunction with other application circuits, the
relay in the Kohler circuit is specially congured with a 680 ohm resistor in parallel with the relay coil. This is
done to negate transient voltage signals that would be normally created by interrupting the relay current once
the relay has been activated. Therefore, relay replacement must only be made with the properly identied relay.
Insert stator leads into connector
slots shown either orientation is
acceptable
Wiring
Harness
Insert relay into harness
connector as shown
Wire Tie
(Black)
Center slot is empty
Position connector with relay approximately as
shown and attach to starter with wire tie
Section 7
Push Wing
Mount
(Black)
Figure 7-13. Stator Brake and Relay Harness Connections.
Troubleshooting Stator Brake System
Problems that could occur with the Kohler portion
circuit generally could be caused by two component
failures or an incorrect relay replacement, which will
create the following conditions:
Dead Battery
The brake relay has failed and is keeping the stator
shorted, so no charge current can be passed from the
rectifier-regulator to the baery, eventually allowing
the baery to discharge.
Test
Check baery voltage using a test meter with the
application off and then while the application is
operating at maximum speed. The baery voltage
should increase from the engine off condition to the
engine full speed condition.
If it does not, shut down the engine, remove the relay
from its socket and re-test at full engine speed.
If the baery voltage does not increase with the engine
operating, the problem is likely not with the stator
brake relay.
Engine will crank but will not start
The brake stator relay is interacting with the
application safeties or the reverse mow electronics,
preventing normal engine start up.
Test
Remove the brake relay from its socket and aempt
to restart the engine. If the engine starts, it is likely
that the relay is not correct for this application or the
transient protection resistor has failed. Replace the
relay with the correct component.
If the engine does not start, the problem may
exist with the application reverse mow circuit, the
application safeties or with the key switch keeping the
ignition shutdown line tied to engine ground.
Remove the engine shutdown (kill) lead from the
application wire harness and aempt to start the
engine again.
If the engine still does not start, you may have a fuel
or ignition problem.
7
Perform other test associated with the charging stator
and rectifier-regulator to further determine root cause.
7.15
Page 68
Section 7
Electrical System and Components
Electric Starters
These engines use inertia drive starting motors.
Operation
When power is applied to the starter, the armature
rotates. As the armature rotates, the drive pinion
moves out on the splined drive sha and into mesh
with the flywheel ring gear. When the pinion reaches
the end of the drive sha, it rotates the flywheel and
cranks the engine.
When the engine starts, the flywheel rotates faster
than the starter armature and drive pinion. This
moves the drive pinion out of mesh with the ring
gear and into the retracted position. When power is
removed from the starter, the armature stops rotating
and the drive pinion is held in the retracted position
by the anti-dri spring.
Starting Motor Precautions
NOTE: Do not crank the engine continuously for
more than 10 seconds at a time. If the engine
does not start, allow a 60-second cool-down
period between starting aempts. Failure
to follow these guidelines can burn out the
starter motor.
NOTE: If the engine develops sufficient speed to
disengage the inertia drive starter but does
not keep running (a false start), the engine
rotation must be allowed to come to a
complete stop before aempting to restart
the engine. If the starter is engaged while the
flywheel is rotating, the starter pinion and
flywheel ring gear may clash, resulting in
damage to the starter.
NOTE: If the starter does not crank the engine, shut
off the starter immediately. Do not make
further aempts to start the engine until the
condition is corrected.
NOTE: Do not drop the starter or strike the starter
frame or end cap. Doing so can damage the
starter.
Troubleshooting Guide - Starting Difficulties
Problem
Starter
Does Not
Energize
Starter
Energizes
But Turns
Slowly
Possible FaultCorrection
Battery
Wiring
Starter Switch
or Solenoid
Battery
Brushes
Transmission
or
Engine
1. Check the specific gravity of baery. If low, recharge or replace
baery as necessary.
1. Clean corroded connections and tighten loose connections.
2. Replace wires in poor condition.
1. Bypass the switch or solenoid with a jumper wire. If starter cranks
normally, replace the faulty components.
1. Check the specific gravity of baery. If low, recharge or replace
baery as necessary.
2. Baery too small, must be at least 250 cold-cranking amps.
1. Check for excessively dirty or worn brushes and commutator.
Clean commutator using a coarse cloth (not emery cloth).
2. Replace brushes if excessively or unevenly worn.
1. Make sure the clutch or transmission is disengaged or placed in
neutral. This is especially important on equipment with
hydrostatic drive. The transmission must be exactly in neutral to
prevent resistance which could keep the engine from starting.
2. Check for seized engine components such as the bearings,
connecting rod, and piston.
7.16
Page 69
Starter Removal and Installation
Refer to the Disassembly and Reassembly Sections for
starter removal and installation procedures.
Starter Drive Service
Every 500 hours of operation, clean and lubricate the
splines on the starter drive sha. If the drive pinion
is worn, or has chipped or broken teeth, it must be
replaced. See Figure 7-14.
It is not necessary to completely disassemble the
starter to service the drive components.
Section 7
Electrical System and Components
Figure 7-15. Assembling Inner Half of Tool Around
The Armature Shaft and Retaining Ring.
Spring
Retainer
Drive Nut (Collar)
Figure 7-14. Drive Components.
1. Disassemble the retaining ring, use tool (See
Section 2).
2 Referring to Figure 7-14, grasp the spring retainer
and push it toward the starter, compressing the
anti-dri spring and exposing the retaining ring.
3. Holding the spring retainer in the retracted
position, assemble the inner halves of the removal
tool around the armature sha with the retaining
ring in the inner groove (see Figure 7-15). Slide
the collar over the inner halves to hold them in
position.
Retaining
Ring
AntiDrift
Spring
Drive
Pinion
4. Thread the center screw into the removal tool
until you feel resistance. Use a wrench (1 1/8" or
adjustable) to hold the base of the removal tool.
Use another wrench or socket (1/2" or 13 mm) to
turn the center screw clockwise (see Figure 7-16).
The resistance against the center screw will tell
you when the retaining ring has popped out of
the groove in the armature sha.
7
Figure 7-16. Holding Tool and Turning Center
Screw (Clockwise) to Remove Retaining Ring.
5. Remove the drive components, and drive nut
(collar) from the armature sha, paying aention
to the sequence. If the splines are dirty, clean
them with solvent.
6. The splines should have a light film of lubricant.
Relubricate as necessary with Kohler bendix
starter lubricant (See Section 2). Reinstall or
replace the drive components, assembling them
in the same sequence as they were removed.
7.17
Page 70
Section 7
Electrical System and Components
Retaining Ring Installation
1. Position the retaining ring in the groove in one of
the inner halves. Assemble the other half over the
top and slide on the outer collar.
2. Be certain the drive components are installed in
correct sequence onto the armature sha.
3. Slip the tool over the end of the armature sha, so
the retaining ring inside is resting on the end of
the sha. Hold the tool with one hand, exerting
slight pressure toward the starter. Tap the top
of the tool with a hammer until you feel the
retaining ring snap into the groove. Disassemble
and remove the tool.
4. Squeeze the retaining ring with pliers to
compress it into the groove.
5. Assemble the inner halves with the larger cavity
around the spring retainer (see Figure 7-17). Slide
the collar over them and thread the center screw
in until resistance is felt.
3. Remove the thru bolts and recessed hex nuts.
4. Remove the commutator end cap and li out
the brush carrier assembly with the brushes and
springs.
5. Remove the drive end cap, then pull the armature
with the thrust washer and wave washer (as
equipped) out of the starter frame.
Retaining Ring
Retainer
Anti-Drift Spring
Pinion
Drive Nut (Collar)
Hex Flange Nuts
Drive End Cap
Thrust Washer
Figure 7-17. Assembling Larger Inner Half Around
Spring Retainer.
6. Hold the base of the tool with a 1 1/8" wrench
and turn the center screw clockwise with a 1/2"
or 13 mm wrench to draw the spring retainer up
around the retaining ring. Stop turning when the
resistance increases. Disassemble and remove the
tool.
Starter Disassembly
1. Remove the drive components following the
instructions for servicing the drive.
2. Remove the hex flange nut and insulating washer
from the positive (+) brush lead stud.
Wave Washer
Armature
Frame Assembly
Brush Carrier Assembly
Commutator End Cap
Insulating Washer
Hex Flange Nut
Thru Bolts
Figure 7-18. Inertia Drive Electric Starter.
7.18
Page 71
Section 7
Electrical System and Components
Brush Replacement
1. Remove the hex flange nut and insulating washer
from the positive (+) brush lead stud.
2. Remove the thru bolts and captured hex nuts.
3. Remove the commutator end cap, then pull the
brush carrier assembly out of the frame. See
Figure 7-19.
Figure 7-19. Removing Brush Carrier Assembly.
Commutator Service
Clean the commutator with a coarse, lint free cloth. Do
not use emery cloth.
If the commutator is badly worn or grooved, turn it
down on a lathe or replace the armature.
2. Insert the armature into the starter frame. The
magnets will hold it in place. See Figure 7-21.
Figure 7-21. Armature Installed in Starter Frame.
3. Align the holes with the spaces between the
magnets and install the drive end cap onto the
front of the frame.
4. If the brush assembly is not being replaced,
position the springs and brushes within their
pockets in the carrier; move them to the retracted
position, and install carton staples to retain them.
See Figure 7-22. Replacement brushes come
pre-assembled in the carrier housing, retained
with two carton staples.
7
Starter Reassembly
1. Place the wave washer, followed by the thrust
washer onto the drive sha of the armature. See
Figure 7-20.
Figure 7-20. Washers Installed on Armature.
Figure 7-22. Brush Carrier Assembly with Staples.
7.19
Page 72
Section 7
Electrical System and Components
5. Hold the brush holder assembly with the positive
brush lead stud up. Align the molded sections
with the corresponding cutouts in the starter
frame and slide the brush carrier assembly into
place. The commutator will push the carton
staples out as the brush assembly is inserted. See
Figure 7-23.
Figure 7-23. Installing Brush Carrier Using Staples.
6. Position the commutator end cap over the brush
assembly, aligning the holes for the stud terminal
and the thru bolts.
8. Install the insulating washer and hex flange nut
onto the positive (+) brush lead stud. Make sure
the stud is centered and does not touch the metal
end cap. Torque the hex flange nut to 2.2-4.5 N·m (20-40 in. lb.).
NOTE: Aer installation and connection of the
starter lead, torque the outer nut to
1.6-2.8 N·m (12-25 in. lb.), do not
over torque.
9. Lubricate the drive sha with Kohler bendix
starter drive lubricant (See Section 2). Install
the drive components following the instructions
for servicing the drive. The completed starter is
shown in Figure 7-25.
7. Install the thru bolts and hex nuts. Torque to
3.3-3.9 N·m. (30-35 in. lb.). See Figure 7-24.
Figure 7-24. Torquing Thru Bolts.
Figure 7-25. Assembled Starter.
7.20
Page 73
Disassembly
Section 8
Disassembly
WARNING: 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. 2) Disconnect negative (-) baery
cable from baery.
Section 8
The following sequence is suggested for complete
engine disassembly. This procedure can be varied to
accommodate options or special equipment.
Clean all parts thoroughly 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.
Typical Disassembly Sequence
1. Drain oil from the crankcase and remove oil filter.
2. Remove blower housing.
3. Disconnect spark plug lead.
4. Remove muffler.
5. Remove rectifier-regulator.
6. Remove electric starter.
7. Remove air cleaner.
8. Remove external governor components,
carburetor and fuel pump.
9. Remove ignition module.
10. Remove grass screen, fan, and flywheel.
11. Remove stator.
12. Remove valve cover and cylinder head.
13. Remove closure plate and wiring harness.
14. Remove cam gears, cam shas, and oil pump.
15. Remove connecting rod and piston.
16. Remove piston from connecting rod.
17. Remove piston rings.
18. Remove cranksha and balance weight assembly.
19. Remove balance weight assembly from
cranksha.
20 Remove governor cross sha.
21. Remove PTO and flywheel side oil seals.
Drain Oil from Crankcase and Remove Oil
Filter
1. Remove the oil drain plug and oil fill cap/
dipstick. See Figure 8-1.
2. Allow ample time for the oil to drain from the
crankcase.
3. Remove and discard the oil filter.
8
Oil Fill Cap/
Dipstick
Oil Filter
Oil Drain
Plug
Figure 8-1. Oil Drain Location, Oil Filter, and Oil
Fill Cap/Dipstick.
8.1
Page 74
Section 8
Disassembly
Remove Oil Sentry™ Pressure Switch
(On Models So Equipped)
1. Disconnect the lead from the Oil Sentry™
pressure switch.
2. Remove the pressure switch from the center
passage or adapter elbow in the closure plate. See
Figure 8-2.
Figure 8-2. Removing Oil Sentry™ Switch.
Remove Muffler
1. Remove the hex flange nuts or 5/16-18 capscrews
aaching the muffler or exhaust system to the
engine. Remove any aached brackets. See Figure
8-4.
1. Remove the four shoulder screws securing the
blower housing to the closure plate. See Figure
8-3.
2. Li the blower housing and separate the spark
plug lead from the corresponding slot.
Figure 8-3. Removing Blower Housing Screws.
Disconnect Spark Plug Lead
1. Carefully pull on the boot section and disconnect
the spark plug lead.
Remove Rectifier-Regulator
1. Unplug the connector from the rectifier-regulator.
2. Remove the two screws securing the rectifierregulator to the crankcase. Remove the rectifierregulator. See Figure 8-5.
Figure 8-5. Removing Rectifier-Regulator.
Remove Electric Starter
1. Disconnect the starter lead from the terminal
stud.
2. Remove the two hex flange nuts securing the
starter to the closure plate. Remove the starter.
See Figure 8-6.
8.2
Page 75
Figure 8-6. Removing Electric Starter.
Remove Air Cleaner
1. Loosen the two knobs and remove the air cleaner
cover. See Figure 8-7.
Section 8
Disassembly
3. Remove the two hex flange nuts, or single nut
and long mounting screw securing the air cleaner
base. See Figure 8-9.
Figure 8-9. Removing Air Cleaner Base Fasteners.
4. Disconnect the breather hose from the valve
cover and remove the air cleaner base and gasket.
See Figure 8-10.
Figure 8-7. Removing Air Cleaner Cover.
2. Remove the precleaner (if so equipped), and the
air cleaner element with the formed rubber seal.
See Figure 8-8.
Figure 8-8. Air Cleaner Components.
8
Figure 8-10. Removing Air Cleaner Base and
Breather Hose.
Remove External Governor Components,
Carburetor, and Fuel Pump
WARNING: 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.
8.3
Page 76
Section 8
Disassembly
1. Shut off the fuel supply. Disconnect the fuel line
from the carburetor inlet fiing. See Figure 8-11.
If a fuel pump is used, disconnect the pulse line
from the fiing on the closure plate. See Figure
8-12.
Figure 8-11. Disconnecting Fuel Line from
Carburetor.
Figure 8-13. Removing Heat Deflector Screw and
Ground Lead.
3. If the carburetor uses a fuel solenoid, carefully
cut the plastic tie strap and disconnect the fuel
solenoid lead from the wiring harness. See Figure
8-14.
Figure 8-12. Disconnecting Pulse Line from Fitting.
2. Remove the heat deflector mounting screw and
special washer, which also secures the ground
lead for the fuel shut-off solenoid, if so equipped.
See Figure 8-13.
8.4
Figure 8-14. Disconnecting Fuel Solenoid Lead.
4. Slide the carburetor outward and disconnect the
throle and choke linkages. See Figure 8-15.
Figure 8-15. Removing Carburetor.
Page 77
5. Mark the mounted position of the speed control
bracket in the sloed holes and remove the two
screws securing the speed control bracket to the
closure plate. Note or mark the governor spring
hole for correct installation later. Unhook the
governor spring, then remove the control bracket
(with fuel pump aached, if equipped) and
linkages from the engine. See Figures 8-16 and
8-17.
Figure 8-16. Removing Speed Control Bracket
from Closure Plate.
Section 8
Disassembly
Figure 8-18. Removing Governor Lever.
7. Remove the carburetor gasket, then carefully
remove the heat deflector and gasket from the
intake stud. The heat deflector is made from
a plastic that is quite brile. Do not pry on
the corners, or you risk cracking/breaking the
deflector. If prying is necessary to loosen the
deflector, carefully pry near the intake stud only.
See Figure 8-19. Remove the mounting stud from
the cylinder only if required.
Figure 8-17. Disconnecting Governor Spring.
6. Loosen the hex flange nut and remove the
governor lever* from the governor cross sha.
See Figure 8-18.
*NOTE: It is recommended that a new governor lever
be installed whenever removal is performed.
8
Figure 8-19. Removing Heat Deflector.
8.5
Page 78
Section 8
Disassembly
8. Remove the insert from the intake port (some
models), if separate from the heat deflector. See
Figure 8-20.
Insert
Figure 8-20. Removing Insert (Some Models).
Remove Ignition Module
1. Disconnect the kill lead from the ignition module.
2. Rotate the flywheel magnet away from the
module.
3. Remove the RFI sheathed spark plug lead with
from retaining clip, if so equipped. See Figure
8-21.
Figure 8-22. Removing Ignition Module.
Remove Grass Screen, Fan, and Flywheel
1. Unsnap the grass screen from the cooling fan. See
Figure 8-23.
Figure 8-23. Removing Grass Screen.
NOTE: Always use a flywheel strap wrench or
flywheel holding tool (see Section 2) to hold
the flywheel when loosening or tightening
the flywheel and fan retaining fasteners. Do
not use any type of bar or wedge between
the fins of the cooling fan, as the fins could
become cracked or damaged.
Figure 8-21. Removing Lead from Clip (RFI
Suppression Equipped Units.
4. Remove the two hex flange screws and the
ignition module. See Figure 8-22.
8.6
2. Remove the retaining screw, washer and the fan
mounting plate, securing the fan and flywheel to
the cranksha. See Figure 8-24.
Page 79
Section 8
Disassembly
Figure 8-24. Removing Fan and Flywheel Mounting
Hardware.
3. Carefully li the cooling fan to disengage the two
drive pins and remove it from the flywheel.
4. Remove the flywheel from the cranksha using a
puller. See Figure 8-25.
NOTE: Always use a puller to remove the
flywheel from the cranksha. Do not
strike the cranksha or flywheel, as they
could be cracked or damaged.
Figure 8-26. Removing Stator.
Remove the Valve Cover and Cylinder Head
1. Remove the seven screws securing the valve cover
and any aached brackets. See Figure 8-27.
8
Figure 8-27. Removing Valve Cover Screws.
2. Remove the valve cover and gasket from the
cylinder head. See Figure 8-28.
Figure 8-25. Removing Flywheel Using Puller.
5. Remove the flywheel key from the crank sha.
Remove the Stator
1. Remove the two screws securing the stator to the
closure plate bosses. See Figure 8-26.
NOTE: To disconnect the B+ or stator leads from
the wiring harness connector, insert a
small screwdriver, or similar narrow flat
blade, and bend down the locking tang
of the terminal(s). Gently pull the lead(s)
out of the connector.
Figure 8-28. Valve Cover and Gasket Details.
8.7
Page 80
Section 8
Disassembly
3. Loosen the inner set screws (T15 TORX) and
back off the rocker arm adjusting nuts. Remove
the push rods and mark them, so they can be
reinstalled in the same location. See Figure 8-29.
Figure 8-29. Loosening Adjustment Set Screw and
Nut.
Figure 8-31. Removing Cylinder Head and Gasket.
6. Remove the drain back check ball (some models)
from the keyhole slot in the crankcase. See Figure
8-32. Models without a check ball have an
internal drain back tube in the crankcase.
4. Remove the six hex flange screws securing the
cylinder head. Note the thick washer used on the
screw closest to the exhaust port. See Figure
8-30.
Washer
Figure 8-30. Removing Cylinder Head Bolts and
Washer.
5. Remove the cylinder head and head gasket. See
Figure 8-31.
Figure 8-32. Removing Drain Back Check Ball
from Crankcase (Some Models).
8.8
Page 81
Disassemble Cylinder Head
NOTE: Before disassembly, mark all valve train
components that will be reused, to assure
they are reassembled on the same side.
1. Remove the spark plug. See Figure 8-33.
Section 8
Disassembly
Figure 8-35. Removing Valves with Spring
Compressor.
Figure 8-33. Removing Spark Plug.
2. Remove the adjustment nuts, pivots and rocker
arms from the pivot studs.
3. Remove the rocker arm pivot studs and push rod
guide plates. See Figure 8-34.
Figure 8-34. Disassembling Rocker Arm
Components.
4. Remove the valves.
a. Compress the valve springs using a valve
spring compressor and remove the keepers.
See Figure 8-35.
Remove Closure Plate
1. Remove the fourteen hex flange screws securing
the closure plate to the crankcase. See Figure
8-36. Note the location and position of any
aached clips or clamps.
8
Figure 8-36. Removing Closure Plate Screws.
2. A gasket is used between the closure plate and
crankcase. If necessary, carefully tap on the
bosses for the starter or oil filter with a so-
faced mallet to loosen. Do not pry on the gasket
surfaces of the crankcase or oil pan, as this can
cause damage resulting in leaks.
b. Remove the compressor; then remove the
valve spring caps, valve springs, and valves.
8.9
Page 82
Section 8
Disassembly
3. Remove the closure plate assembly and gasket.
See Figure 8-37.
4. If the wiring harness needs to be separated from
the closure plate, pry open the clamps and pull
out through the slot.
Figure 8-37. Closure Plate and Gasket Removed
from Crankcase.
Disassemble Closure Plate
1. Remove the governor gear and regulating pin
assembly. Gently pry upward using the blades of
two small screwdrivers. See Figure 8-38.
NOTE: The governor gear is held onto the sha by
small molded tabs in the gear. When the
gear is removed these tabs are destroyed
and the gear must be replaced. Governor
gear removal is required for closure plate
disassembly and cleaning of the oil passages.
2. Remove the six screws securing the oil passage
cover to the closure plate. Remove the cover and
gasket. See Figure 8-39.
Figure 8-39. Removing Oil Passage Cover and
Gasket.
Remove Cam Gears, Cam Shafts, and Oil
Pump
1. Remove the thrust washer(s) and cam gears from
the cam shas. Later models will have a thrust
washer on the exhaust side only. See Figure 8-40.
NOTE: The ACR weight and spring normally
captured by the thrust washer and
installation of closure plate, will fall out if the
exhaust cam gear is turned upside down.
Thrust Washer
(Intake Side) Early
Models Only
Figure 8-38. Removing Governor Gear.
8.10
Figure 8-40. Removing Cam Gears.
Page 83
2. Remove the screws securing the cam levers to the
crankcase. See Figure 8-41. Mark the cam levers
for proper reassembly.
NOTE: Cam Gear assemblies may contain either two
or four rivets. The four rivet design is shown
in figures.
Figure 8-41. Removing Cam Levers.
3. Pull the exhaust side cam sha and sloed thrust
washer, out of the crankcase. See Figure 8-42.
Section 8
Disassembly
Drain Back Tube
Figure 8-43. Removing Drain Back Tube (Some
Models).
NOTE: Engine Serial No. 332740003 and Lower, use
a rubber outlet between the oil pump outlet
and lower main bearing area. Some models
use an open seal with an internal passage to
feed oil to the lower bearing. Some models
use a closed or solid seal, and the cranksha
is crossed-drilled to feed oil to the lower
bearing. See Figure 8-44.
Engine Serial No. 332740003 and Higher, the
outlet of the oil pump is closed and no rubber
seal is used. See Figure 8-45.
Figure 8-42. Removing Exhaust Side Cam Shaft
and Slotted Thrust Washer.
4. If the engine contains an internal drain back
tube, unhook it from the oil pump and pull it
out of the crankcase passage. Check for cracks,
brileness or damage. Replace if questionable in
any way. See Figure 8-43.
Open SealClosed Seal
Figure 8-44. Outlet Seal Styles (Some Models).
Open Outlet Style
(Requires Seal)
Figure 8-45. Pump Outlet Styles.
Closed Outlet Style
8
8.11
Page 84
Section 8
Disassembly
5. Remove the two screws securing the oil pump
and intake side cam sha to the crankcase. If
a drain back tube is used, it may be unhooked
and removed separately or together with oil
pump. Carefully pull upward on the cam sha to
remove the assembly from the crankcase cavity.
A small rubber oil pump outlet seal on the outlet
of the oil pump may become dislodged during
removal. Do not lose it. See Figures 8-44 and 8-46.
Outlet Seal
(Some Models)
Figure 8-46. Intake Cam Shaft and Oil Pump
Assembly.
6. If necessary, the oil pump can be separated from
the intake side cam sha. Provide appropriate
support for the sha, and drive out the lower
pin. The oil pump assembly can then be removed
from the cam sha. See Figure 8-47.
Remove Connecting Rod and Piston
1. Rotate the cranksha so the rod journal is in the
9 o’clock position.
NOTE: If a carbon ridge is present at the top of the
bore, use a ridge reamer to remove it before
aempting to remove the piston.
2. Remove the two hex flange screws and the
connecting rod cap. See Figures 8-48.
Figure 8-48. Removing Connecting Rod Cap.
3. Carefully push the connecting rod and the piston
away from the cranksha and out of the cylinder
bore. See Figure 8-49.
Figure 8-47. Separating Oil Pump Assembly from
Intake Side Cam Shaft.
8.12
Figure 8-49. Removing Piston and Connecting
Rod.
Page 85
Section 8
Disassembly
Remove Piston from Connecting Rod
1. Remove the wrist pin retainer and wrist pin.
Separate the piston from the connecting rod. See
Figure 8-50.
Figure 8-50. Separating Piston from Connecting
Rod.
Remove Piston Rings
1. Remove the top and center compression rings
using a ring expander. See Figure 8-51.
Remove Crankshaft and Balance Weight
Assembly
1. Carefully remove the cranksha and balance
weight assembly from the crankcase. See Figure
8-52. On engines aer Serial No. 3618005223,
carefully li the lower control link (for balance
weight), off the boss of crankcase as the
cranksha is removed. See Figure 8-53.
Figure 8-52. Removing Crankshaft and Balance
Weight Assembly (Before Serial No. 3618005213).
2. Remove the oil control ring rails, then remove the
spacer.
Figure 8-51. Removing Piston Rings.
8
Figure 8-53. Removing Crankshaft and Link (After
Serial No. 3618005223).
8.13
Page 86
Section 8
Disassembly
Balance Weight Disassembly
If necessary, the balance weight assembly can be
separated from the cranksha. Disassemble only if
required.
1. Remove the crank gear from the cranksha and
carefully remove the key from the keyway. See
Figure 8-54.
Figure 8-55. Removing Balance Weight Screw
(Guide Shoe Design Before Serial No. 3618005213).
Figure 8-54. Removing Crank Gear Key.
2. Remove the guide shoe from the guide pin on
the flywheel side of the assembly (Before Serial
No. 3618005213). See Figure 8-55. Remove the
link from the guide pin on the PTO side of the
assembly (Aer Serial No. 3618005223). See
Figure 8-56.
3. Remove the long hex flange screw securing
the two balance weight halves together on the
cranksha. Note the orientation of all parts. The
guide pin is on flywheel side for the balance
weight design with the closure plate side guide
shoe. The guide pin is on PTO side for the
balance weight design with the lower control
link. Hold the guide pin with wrench or torx bit
socket as required. Do not hold or damage the
outside diameter (O.D.) of the guide pin. See
Figure 8-55 or 8-56.
Figure 8-56. Removing Balance Weight Screw and
Guide Pin (Control Link Design After Serial No.
3618005223).
8.14
Page 87
4. Mark the weights for proper reassembly and
carefully slide the balance weights off the
cranksha eccentrics. See Figures 8-57 and 8-58.
Figure 8-57. Disassembled Balance Weight (Guide
Shoe Design Before Serial No. 3618005213).
Section 8
Disassembly
Figure 8-59. Removing Hitch Pin and Washer.
2. Slide the sha inward and remove it through the
inside of the crankcase. Be careful not to lose the
small washer in the inside portion of the sha.
See Figure 8-60.
Figure 8-58. Disassembled Balance Weight
(Control Link Design After Serial No. 3618005223).
Remove Governor Cross Shaft
1. Remove the hitch pin and washer located on the
outside of the governor cross sha. See Figure
8-59.
8
Figure 8-60. Removing Governor Cross Shaft.
Remove PTO and Flywheel Side Oil Seals
1. Use a seal puller to remove the PTO and flywheel
side oil seals. See Figure 8-61.
Figure 8-61. Removing Seal with a Seal Puller.
8.15
Page 88
Section 8
Disassembly
8.16
Page 89
Section 9
Inspection and Reconditioning
Section 9
Inspection and Reconditioning
This section covers the operation, inspection, and repair/reconditioning of major internal engine components.
The following components are not covered in this section. They are covered in sections of their own:
Air Cleaner, Section 4
Carburetor and External Governor, Section 5
Ignition, Charging and Electric Starter, Section 7
Clean all parts thoroughly. 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. Use gasket
remover to remove old material from the valve cover, cylinder head, crankcase, and oil pan. Do not scrape the
gasket surfaces, as this could cause damage that results in leaks.
Make sure all traces of cleaning solvents 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.
Refer to A Guide to Engine Rebuilding (TP-2150) for additional information. Measurement Guide (TP-2159-A)
and Engine Inspection Data Record (TP-2435) are also available; use these to record inspection results.
Automatic Compression Release (ACR)
This engine is equipped with an Automatic
Compression Release (ACR) mechanism. The ACR
lowers compression at cranking speeds to make
starting easier.
Operation
The ACR mechanism consists of an actuating spring
and a pivoting flyweight/control pin assembly,
located in the exhaust side cam gear. A thrust washer
and mounting of the closure plate hold the ACR in
position. See Figure 9-1. At cranking speeds (700 RPM
or lower), the spring holds the flyweight in and the
rounded surface of the control pin protrudes above
the exhaust cam lobe. This pushes the exhaust valve
off its seat during the first part of the compression
stroke. The compression is reduced to an effective
ratio of about 2:1 during cranking.
When the engine is stopped, the spring returns the
flyweight/control pin assembly to the compression
release position, ready for the next start.
Control Pin
Lower Section
Cam Lobe
Flyweight
Cam Gear
Spring
9
Aer starting, when engine speed exceeds 700 RPM,
centrifugal force overcomes the force of the flyweight
spring. The flyweight moves outward, rotating the
control pin to expose the flat surface, which is lower
than the cam lobe. The control pin no longer has any
effect on the exhaust valve, and the engine operates at
full power.
Thrust Washer
Figure 9-1. ACR Details.
9.1
Page 90
Section 9
Inspection and Reconditioning
Benefits
Reducing the compression at cranking speeds results
in several important benefits.
1. The starter and baery can be smaller, more
practical for the applications in which these
engines are used.
2. ACR eliminates kickback during starting, so a
spark retard/advance mechanism is no longer
required.
3. The choke control seing is less critical with ACR.
In the event of flooding, excess fuel is blown out
the opened exhaust valve and does not hamper
starting.
4. Engines with ACR start much faster in cold
weather.
5. Engines with ACR can be started with spark
plugs that are worn or fouled. Engines without
ACR would be less likely to start with the same
plugs.
Cam Gears
Inspection and Service
Inspect the gear teeth and cam lobes of the intake and
exhaust cam gears. If the lobes exhibit excessive wear,
or the teeth are worn, chipped or broken, replacement
of the cam gear(s) will be necessary.
Crankshaft and Crank Gear
Inspection and Service
Inspect the teeth of the crank gear. If the teeth
are badly worn, chipped, or some are missing,
replacement of the crank gear will be necessary.
Remove the gear by pulling it off the key and
cranksha.
Inspect the cranksha bearing journal surfaces for
wear, scoring, grooving, etc. If they show signs of
damage or are out of running clearance specifications,
the cranksha must be replaced.
Inspect the cranksha keyways. If worn or chipped,
replacement of the cranksha will be necessary.
Inspect the crankpin for wear, score marks or
aluminum transfer. Slight score marks can be cleaned
with crocus cloth soaked in oil. If wear limits are
exceeded (see Section 1), it will be necessary to replace
the cranksha.
Crankcase
Inspection and Service
Check all gasket surfaces to make sure they are free of
gasket fragments and deep scratches or nicks.
Check the cylinder wall for scoring. In severe cases,
unburned fuel can wash the necessary lubricating
oil off the piston and cylinder wall. The piston rings
make metal to metal contact with the wall, causing
scuffing and scoring. Scoring of the cylinder wall can
also be caused by localized hot spots from blocked
cooling fins or from inadequate or contaminated
lubrication.
If the cylinder bore is scored, worn, tapered, or outof-round, resizing may be possible. Use an inside
micrometer or telescoping gauge to determine the
amount of wear (refer to Section 1). If wear exceeds
the published limits, a 0.08 mm (0.003 in.) oversize
piston is available. If the cylinder will not clean
up at 0.08 mm (0.003 in.) oversize, a short block or
replacement engine will need to be considered.
Honing
While most commercially available cylinder hones
can be used with either portable drills or drill presses,
the use of a low speed drill press is preferred as it
facilitates more accurate alignment of the bore in
relation to the cranksha counter bore. Honing is best
accomplished at a drill speed of about 250 RPM and
60 strokes per minute. Aer installing coarse stones in
hone, proceed as follows:
1. Lower the hone into the bore and, aer centering,
adjust it so that the stones are in contact with
the cylinder wall. Use of a commercial cuing-
cooling agent is recommended.
2. With the lower edge of each stone positioned
even with the lowest edge of the bore, start the
drill and honing process. Move the hone up and
down while resizing to prevent the formation of
cuing ridges. Check the size frequently. Make
sure the bore is cool when measuring.
9.2
Page 91
Section 9
Inspection and Reconditioning
3. When the bore is within 0.064 mm (0.0025 in.)
of desired size, remove the coarse stones and
replace with burnishing stones. Continue with
the burnishing stones until within 0.013 mm
(0.0005 in.) of desired size and then use finish
stones (220-280 grit) and polish to final size. A
crosshatch should be observed if honing is done
correctly. The crosshatch should intersect at
approximately 23-33° off the horizontal. Too flat
an angle could cause the rings to skip and wear
excessively, too steep an angle will result in high
oil consumption (refer to Figure 9-2).
Measuring Piston-to-Bore Clearance
Before installing the piston into the cylinder bore, it
is necessary that the clearance be accurately checked.
This step is oen overlooked, and if the clearances are
not within specifications, engine failure will usually
result.
NOTE: Do not use a feeler gauge to measure piston-
to-bore clearance – it will yield inaccurate
measurements. Always use a micrometer.
Use the following procedure to accurately measure
the piston-to-bore clearance:
1. Use a micrometer and measure the diameter of
the piston perpendicular to the piston pin, up
8 mm (0.314 in.) from the boom of the piston
skirt as indicated in Figure 9-3.
Measure 8 mm (0.314 in.) Above the Bottom of
Piston Skirt at Right Angles to Piston Pin.
Figure 9-2. Cylinder Bore Crosshatch after Honing.
4. Aer honing, check the bore for roundness, taper,
and size. Use an inside micrometer, telescoping
gauge, or bore gauge to take measurements.
The measurements should be taken at three
locations in the cylinder – at the top, middle,
and boom. Two measurements should be taken
(perpendicular to each other) at each of the three
locations.
Clean Cylinder Bore after Honing
Proper cleaning of the cylinder walls following honing
is critical. Grit le in the cylinder bore can destroy
an engine in less than one hour of operation aer a
rebuild.
The final cleaning operation should always be a
thorough scrubbing with a brush and hot, soapy
water. Use a strong detergent that is capable of
breaking down the machining oil while maintaining
a good level of suds. If the suds break down during
cleaning, discard the dirty water and start again
with more hot water and detergent. Following the
scrubbing, rinse the cylinder with very hot, clear
water, dry it completely, and apply a light coating of
engine oil to prevent rusting.
8 mm (0.314 in.)
Figure 9-3. Measuring Piston Diameter.
2. Use an inside micrometer, telescoping gauge, or
bore gauge and measure the cylinder bore. Take
the measurement approximately 63.5 mm (2.5 in.) below the top of the bore and
perpendicular to the piston pin.
3. Piston-to-bore clearance is the piston diameter
subtracted from the bore diameter (step 2 minus
step 1).
Balance Weight Assembly
The balance weight assembly counterbalances
the cranksha weights and internal forces during
operation to minimize vibration. Several key areas of
the balance weight must be checked before installation
and use. Additionally, the mating components
(cranksha eccentrics and closure plate guide channel)
must also be inspected for wear or damage.
Use the following procedure to check the balance
weight and matching components.
9
9.3
Page 92
Section 9
Inspection and Reconditioning
Balance Weight-to-Eccentric Clearance
Before the balance weight assembly is reassembled to
the cranksha, the running clearance to the cranksha
eccentrics must be accurately checked. Failure
to maintain the required clearances will result in
vibration or engine failure.
NOTE: Do not use a feeler gauge to measure balance
weight-to-eccentric clearance.
Measuring Balance Weight to Crankshaft
Eccentric Ring(s) Clearance
1. Use an inside micrometer, telescoping gauge,
or bore gauge and measure the inside diameter
of the balance weight bearing surface. Take two
measurements 90° to each other on each weight.
See Figure 9-4.
3. The running clearance is the eccentric
diameter subtracted from the balance weight
bearing diameter (step 1 minus step 2). If
the measurements are outside the maximum
take two measurements 90° to each other. See
Figure 9-5.
Figure 9-6. Measuring Balance Weight Guide Shoe.
2. Use an inside micrometer, telescoping gauge or
similar tool and measure the width of the guide
channel in the closure plate. See Figure 9-7.
Record these dimensions.
Figure 9-7. Measuring Guide Channel in Closure
Plate.
Figure 9-5. Measuring Crankshaft Eccentric.
9.4
Page 93
Section 9
Inspection and Reconditioning
3. Use an outside micrometer again and measure
the O.D. of the balance weight guide pin. See
Figure 9-8.
Figure 9-8. Measuring Guide Pin O.D.
4. Use a split ball gauge or dial calipers and
measure the I.D. of the corresponding hole in
the guide shoe. See Figure 9-9. Record these
dimensions.
Flywheel
Inspection
Inspect the flywheel for cracks and check the keyway
for wear or damage. Replace the flywheel if cracked. If
the flywheel key is sheared or the keyway is damaged,
replace the cranksha, flywheel, and key.
Inspect the ring gear for cracks or damage. Ring gears
are not available separately. Replace the flywheel if the
ring gear is damaged.
Figure 9-9. Measuring Guide Shoe Hole I.D.
If any of the measurements taken are outside the
maximum wear limits listed in Section 1, the affected
component(s) must be replaced.
9
9.5
Page 94
Section 9
Inspection and Reconditioning
Cylinder Head and Valves
Inspection and Service
Carefully inspect the valve mechanism parts. Inspect the valve springs and related hardware for excessive wear
or distortion. Check the valves and valve seats for evidence of deep piing, cracks, or distortion. Check the
running clearance between the valve stems and guides. See Figure 9-10 for valve details and specifications.
Exhaust Valve
F
B
Intake Valve
E
D
G
A
C
A
C
E
D
F
G
B
A
B
C
D
E
F
G
Figure 9-10. Valve Details.
9.6
Seat Angle
Guide Depth
Guide I.D.
Valve Head Diameter
Valve Face Angle
Valve Margin (Min.)
Valve Stem Diameter
Dimension
IntakeExhaust
89°
10.20 mm
6.038/6.058 mm
37.625/37.375 mm
45°
1.5 mm
5.982/6.000 mm
89°
6.2 mm
6.038/6.058 mm
32.125/32.375 mm
45°
1.5 mm
5.970/5.988 mm
Page 95
Section 9
Inspection and Reconditioning
Hard starting, or loss of power accompanied by high fuel consumption, may be symptoms of faulty valves.
Although these symptoms could also be aributed to worn rings, remove and check the valves first. Aer
removal, clean the valve heads, faces, and stems with a power wire brush. Then, carefully inspect each valve for
defects such as warped head, excessive corrosion, or worn stem end. Replace valves found to be in bad condition.
A normal valve and valves in bad condition are shown in the accompanying illustrations.
Normal: Even aer long hours of operation a valve
can be reconditioned and reused if the face and
margin are in good shape. If a valve is worn to where
the margin is less than 1/32" do not reuse it. The valve
shown was in operation for almost 1000 hours under
controlled test conditions.
Bad Condition: The valve depicted here should be
replaced. Note the warped head; margin damaged
and too narrow. These conditions could be aributed
to excessive hours or a combination of poor operating
conditions.
Leakage: A poor grind on a valve face or seat will
allow leakage, resulting in a valve burned on one side
only.
9
Coking: Coking is normal on intake valves and is not
harmful. If the seat is good, the valve could be reused
aer cleaning.
9.7
Page 96
Section 9
Inspection and Reconditioning
Excessive Combustion Temperatures: The white
deposits seen here indicate very high combustion
temperatures, usually due to a lean fuel mixture.
Stem Corrosion: Moisture in fuel or from
condensation are the most common causes of valve
stem corrosion. Condensation occurs from improper
preservation during storage and when engine is
repeatedly stopped before it has a chance to reach
normal operating temperatures. Replace corroded
valves.
Gum: Gum deposits usually result from using stale
gasoline. This condition is oen noted in applications
where fuel is not drained out of tank during the off
season. Gum is a prevalent cause of valve sticking.
The cure is to ream the valve guides and clean or
replace the valves, depending on their condition.
9.8
Overheating: An exhaust valve subject to overheating
will have a dark discoloration in the area above the
valve guide. Worn guides and faulty valve springs
may cause this condition. Also check for clogged air
intake, and blocked fins when this condition is noted.
Page 97
Valve Guides
If a valve guide is worn beyond specifications, it will
not guide the valve in a straight line. This may result
in burned valve faces or seats, loss of compression,
and excessive oil consumption.
To check valve guide-to-valve stem clearance,
thoroughly clean the valve guide and, using a splitball gauge, measure the inside diameter. Then, using
an outside micrometer, measure the diameter of
the valve stem at several points on the stem where
it moves in the valve guide. Use the largest stem
diameter to calculate the clearance. If the intake
clearance exceeds 0.038/0.076 mm (0.0015/0.0030 in.) or
the exhaust clearance exceeds 0.050/0.088 mm (0.0020/0.0035 in.), determine whether the valve stem
or guide is responsible for the excessive clearance.
Maximum (I.D.) wear on the intake valve guide is
6.135 mm (0.2415 in.) while 6.160 mm (0.2425 in.)
is the maximum allowed on the exhaust guide. The
guides are not removable. If the guides are within
limits but the valve stems are worn beyond limits,
replace the valves.
Valve Seat Inserts
Hardened steel alloy intake and exhaust valve
seat inserts are press fied into the cylinder head.
The inserts are not replaceable, but they can be
reconditioned if not too badly pied or distorted. If
the seats are cracked or badly warped, the cylinder
head should be replaced.
Recondition the valve seat inserts following the
instructions provided with the valve seat cuer being
used. A typical cuer is shown in Figure 9-11. The final
cut should be made with an 89° cuer as specified for
the valve seat angle in Figure 9-10. With the proper 45°
valve face angle, and the valve seat cut properly (44.5°
as measured from centerline when cut 89°) this would
result in the desired 0.5° (1.0° full cut) interference
angle where the maximum pressure occurs on the
valve face and seat.
Section 9
Inspection and Reconditioning
Valve Seat Cutter
Pilot
Figure 9-11. Typical Valve Seat Cutter.
Lapping Valves
Reground or new valves must be lapped in, to provide
a good seal. Use a hand valve grinder with suction
cup for final lapping. Lightly coat valve face with fine
grade of grinding compound, then rotate valve on seat
with grinder. Continue grinding until smooth surface
is obtained on seat and on valve face. Thoroughly
clean cylinder head in soap and hot water to remove
all traces of grinding compound. Aer drying cylinder
head, apply a light coating of engine oil to prevent
rusting.
Pistons and Rings
Inspection
Scuffing and scoring of pistons and cylinder walls
occurs when internal temperatures approach the
welding point of the piston. Temperatures high
enough to do this are created by friction, which is
usually aributed to improper lubrication, and/or
overheating of the engine.
Normally, very lile wear takes place in the piston
boss-piston pin area. If the original piston and
connecting rod can be reused aer new rings are
installed, the original pin can also be reused, but new
piston pin retainers are required. The piston pin is part
of the piston assembly; if the pin boss or the pin are
worn or damaged, a new piston assembly is required.
9
Ring failure is usually indicated by excessive oil
consumption and blue exhaust smoke. When rings
fail, oil is allowed to enter the combustion chamber
where it is burned along with the fuel. High oil
consumption can also occur when the piston ring
end gap is incorrect because the ring cannot properly
conform to the cylinder wall under this condition. Oil
control is also lost when ring gaps are not staggered
during installation.
9.9
Page 98
Section 9
Inspection and Reconditioning
When cylinder temperatures get too high, lacquer and
varnish collect on pistons causing rings to stick which
results in rapid wear. A worn ring usually takes on a
shiny or bright appearance.
Scratches on rings and pistons are caused by abrasive
material such as carbon, dirt, or pieces of hard metal.
Detonation damage occurs when a portion of the fuel
charge ignites spontaneously from heat and pressure
shortly aer ignition. This creates two flame fronts
that meet and explode to create extreme hammering
pressures on a specific area of the piston. Detonation
generally occurs from using low octane fuels.
Preignition or ignition of the fuel charge before the
timed spark can cause damage similar to detonation.
Preignition damage is oen more severe than
detonation damage. Preignition is caused by a hot
spot in the combustion chamber from sources such
as glowing carbon deposits, blocked fins, improperly
seated valve, or wrong spark plug. See Figure 9-12 for
some common types of piston and ring damage.
Replacement pistons are available in STD and 0.08 mm (0.003 in.) oversize, which include new rings and
piston pins. Service replacement piston ring sets are
also available separately. Always use new piston rings
when installing pistons. Never reuse old rings.
The cylinder bore must be deglazed before service
ring sets are used.
Overheated or Deteriorated Oil
Figure 9-12. Common Types of Piston and Ring Damage.
9.10
Abrasive Scratched RingsStuck, Broken Rings
Scored Piston and Rings
Page 99
Some important points to remember when servicing
piston rings:
1. If the cylinder bore is within the wear limits (refer
to Section 1) and the old piston is within wear
limits, free of score or scuff marks, the old piston
may be reused.
2. Remove old rings and clean up grooves. Never
reuse old rings.
3. Before installing the rings on the piston, place
each of the top two rings in its running area in the
cylinder bore and check the end gap (see Figure
9-13). Compare to the listed specifications.
Top and Middle Compression Ring End Gap
New Bore
Top Ring .....................0.15/0.40 mm (0.006/0.016 in.)
Middle Ring ............... 0.30/0.55 mm (0.012/0.022 in.)
Max. Used Bore .........0.77 mm (0.030 in.)
Section 9
Inspection and Reconditioning
Figure 9-14. Measuring Piston Ring Side
Clearance.
Install Piston Rings
To install piston rings, proceed as follows:
NOTE: Rings must be installed correctly. Ring
installation instructions are usually included
with new ring sets. Follow instructions
carefully. Use a piston ring expander to
install rings. Install the boom (oil control)
ring first and the top compression ring last.
Refer to Figure 9-15.
Figure 9-13. Measuring Piston Ring End Gap.
4. Aer installing the new compression (top and
middle) rings on the piston, check piston-to-ring
side clearance. The maximum recommended side
clearance for each ring is 0.04 mm (0.0016 in.). If
the side clearance is greater than specified, a new
piston must be used. Refer to Figure 9-14.
Top Compression Ring-to-Groove
Side Clearance ................................0.04 mm (0.0016 in.)
Middle Compression Ring-to-Groove
Side Clearance ...............................0.04 mm (0.0016 in.)
Piston Ring
End Gap
Identification
Mark
Piston
Top Compression
Ring
Center Compression
Ring
Rails
Oil Control Ring
(Three Piece)
Figure 9-15. Piston Ring Installation.
Expander
9
9.11
Page 100
Section 9
Inspection and Reconditioning
1. Oil Control Ring (Boom Groove): Install the
expander and then the rails. Make sure the ends
of the expander are not overlapped.
2. Compression Ring (Center Groove): Install the
center ring using a piston ring installation tool.
Make sure the identification mark is up when the
ring is installed.
3. Compression Ring (Top Groove): Install the top
ring using a piston ring installation tool. Make
sure the identification mark is up when the ring
is installed.
Connecting Rods
Inspection and Service
Check the bearing area (big end) for score marks and
excessive wear (measure running and side clearances;
refer to Section 1. Service replacement connecting rods
are available in STD crankpin size.
Oil Pump Assembly and Pressure Relief
Valve
Inspection and Service
The closure plate must be removed to inspect and
service the oil pump. Refer to the Disassembly and
Reassembly Sections (8 and 10) for removal and
reinstallation procedures. Check the oil pump and
gears for cracks, damage, wear, and smooth rotation.
Replace the pump if any binding is noted or reuse is
questionable in any way.
A pressure relief valve is built into the oil pump to
limit maximum pressure. It is not serviceable. If a
problem exists with the pressure relief valve, the oil
pump assembly should be replaced.
Oil Passages
Figure 9-16. Oil Passages in Closure Plate.
Oil Passages
Figure 9-17. Oil Passages in Passage Cover.
Use a new passage cover gasket and install the passage
cover onto the closure plate. Reinstall the six mounting
screws and torque to 4.0 N·m (35 in. lb.), following the
sequence in Figure 9-18.
Closure Plate and Passage Cover
Inspection and Service
If disassembly was performed, inspect and ensure the
oil passages in the closure plate and the passage cover
are completely clean and not obstructed in any way.
See Figures 9-16 and 9-17. Check straightness of the
passage cover if required, against a flat surface.
9.12
4
1
Figure 9-18. Torque Sequence for Passage Cover.
5
6
2
3
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