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KOHLER COMMand Model CH730 CH25 25HP Engine Full Service & Repair Manual
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SERVICE MANUAL
HORIZONTAL CRANKSHAFT
COMMAND CH18-750

Contents
Section 1. Safety and General Information ............................................................................
Section 2. Special Tools ..........................................................................................................
Section 3. Troubleshooting .....................................................................................................
Section 4. Air Cleaner and Air Intake System ........................................................................
Section 5. Fuel System and Governor ....................................................................................
Section 5A. LPG Fuel Systems ...............................................................................................
Section 5B. Electronic Fuel Injection (EFI) Fuel System ......................................................
Section 6. Lubrication System ................................................................................................
Section 7. Retractable Starter .................................................................................................
Section 8. Electrical System and Components .....................................................................
Section 9. Disassembly ...........................................................................................................
Section 10. Inspection and Reconditioning ...........................................................................
Section 11. Reassembly ...........................................................................................................
Section 12. Clutch ....................................................................................................................
2
1
8
9
10
11
12
4
5
6
7
3
5A
5B

1.1
1
Section 1
Safety and General Information
Safety Precautions
To ensure safe operation please read the following statements and understand their meaning. Also
refer to your equipment manufacturer's manual for other important safety information. This manual
contains safety precautions which are explained below. Please read carefully.
WARNING
Warning is used to indicate the presence of a hazard that can cause severe personal injury, death,
or substantial property damage if the warning is ignored.
CAUTION
Caution is used to indicate the presence of a hazard that will or can cause minor personal injury or
property damage if the caution is ignored.
NOTE
Note is used to notify people of installation, operation, or maintenance information that is important
but not hazard-related.
For Your Safety!
These precautions should be followed at all times. Failure to follow these precautions could result in injury to yourself
and others.
Rotating Parts can cause severe
injury.
Stay away while engine is in
operation.
WARNING
Rotating Parts!
Keep hands, feet, hair, and clothing away
from all moving parts to prevent injury.
Never operate the engine with covers,
shrouds, or guards removed.
Hot Parts can cause severe burns.
Do not touch engine while operating
or just after stopping.
WARNING
Hot Parts!
Engine components can get extremely
hot from operation. To prevent severe
burns, do not touch these areas while the
engine is running - or immediately after it
is turned off. Never operate the engine
with heat shields or guards removed.
Accidental Starts can cause severe
injury or death.
Disconnect and ground spark plug
leads before servicing.
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(s). 2)
Disconnect negative (-) battery cable
from battery.

1.2
Section 1
Safety and General Information
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.
WARNING WARNING
Electrical Shock can cause injury.
Do not touch wires while engine is
running.
CAUTION
Uncoiling Spring can cause severe
injury.
Wear safety goggles or face
protection when servicing
retractable starter.
WARNING
Explosive Gas can cause fires and
severe acid burns.
Charge battery only in a well
ventilated area. Keep sources of
ignition away.
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.
Spring Under Tension!
Retractable starters contain a powerful,
recoil spring that is under tension.
Always wear safety goggles when
servicing retractable starters and
carefully follow instructions in the
"Retractable Starter" Section 7 for
relieving spring tension.
Explosive Gas!
Batteries produce explosive hydrogen gas
while being charged. To prevent a fire or
explosion, charge batteries only in well
ventilated areas. Keep sparks, open
flames, and other sources of ignition
away from the battery at all times. Keep
batteries out of the reach of children.
Remove all jewelry when servicing
batteries.
Before disconnecting the negative (-)
ground cable, make sure all switches are
OFF. If ON, a spark will occur at the
ground cable terminal which could cause
an explosion if hydrogen gas or gasoline
vapors are present.
Explosive Fuel can cause fires and
severe burns.
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.
Cleaning Solvents can cause severe
injury or death.
Use only in well ventilated areas
away from ignition sources.
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.
Electrical Shock!
Never touch electrical wires or
components while the engine is running.
They can be sources of electrical shock.
Do not fill the fuel tank while the
engine is hot or running.

1.3
Section 1
Safety and General Information
1
A. Model No.
Version Code
S = Electric Start
C H 18 S
Engine Identification Numbers
When ordering parts, or in any communication
involving an engine, always give the Model,
Specification and Serial Numbers, including letter
suffixes if there are any.
The engine identification numbers appear on a decal,
or decals, affixed to the engine shrouding. See Figure
1-1. An explanation of these numbers is shown in
Figure 1-2.
Figure 1-1. Engine Identification Decal Location.
Variation of
Basic Engine
B. Spec. No.
62500
Command Engine
Horizontal Crankshaft
Horsepower
17 = 17 HP
18 = 18 HP
20 = 20 HP
22 = 22 HP
23 = 23 HP
25 = 25 HP
26 = 26 HP
Numerical Designation
730
740
745
750
or
Engine Model Code
Code Model
62 CH18
64 CH20
66 CH22 (624 cc)
68 CH25
76 CH22/23 (674 cc)
78 CH26
CH730-0001
CH740-0001
CH745-0001
CH750-0001
Complete Spec Number
(Incorporating Model No.
with Variation No. of
Basic Spec.)
or
Figure 1-2. Explanation of Engine Identification Numbers.
C. Serial No.
Year Manufactured Code
Code Y ear
21 1991
22 1992
23 1993
24 1994
25 1995
26 1996
27 1997
28 1998
29 1999
Factory Code
3305810334
Code Y ear
30 2000
31 2001
32 2002
33 2003
34 2004
35 2005
36 2006
37 2007
Identification Decal

1.4
Section 1
Safety and General Information
Oil Recommendations
Using the proper type and weight of oil in the
crankcase is extremely important. So is checking oil
daily and changing oil regularly. Failure to use the
correct oil, or using dirty oil, causes premature engine
wear and failure.
Oil Type
Use high-quality detergent oil of API (American
Petroleum Institute) Service Class SG, SH, SJ or higher.
Select the viscosity based on the air temperature at the
time of operation as shown in the following table.
Refer to Section 6 - “Lubrication System” for detailed
procedures on checking the oil, changing the oil and
changing the oil filter.
Fuel Recommendations
WARNING: Explosive Fuel!
Gasoline is extremely flammable and its vapors can explode if
ignited. Before servicing the fuel system, make sure there are no
sparks, open flames or other sources of ignition nearby as these
can ignite gasoline vapors. Disconnect and ground the spark plug
leads to prevent the possibility of sparks from the ignition system.
General Recommendations
Purchase gasoline in small quantities 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 left 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 or higher. In
countries using the Research method, it should be 90
octane minimum.
Unleaded gasoline is recommended as it leaves less
combustion chamber deposits and reduces harmful
exhaust emissions. Leaded gasoline is not recommended
and must not be used on EFI engines, or on other models
where exhaust emissions are regulated.
Gasoline/Alcohol blends
Gasohol (up to 10% ethyl alcohol, 90% unleaded gasoline
by volume) is approved as a fuel for Kohler engines.
Other gasoline/alcohol blends are not approved.
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.
NOTE: Using other than service class SG, SH, SJ or
higher oil or extending oil change intervals
longer than recommended can cause engine
damage.
NOTE: Synthetic oils meeting the listed
classifications may be used with oil changes
performed at the recommended intervals.
However, to allow piston rings to properly
seat, a new or rebuilt engine should be
operated for at least 50 hours using standard
petroleum based oil before switching to
synthetic oil.
A logo or symbol on oil containers identifies the API
service class and SAE viscosity grade. See Figure 1-3.
Figure 1-3. Oil Container Logo.
*
*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).
**

1.5
Section 1
Safety and General Information
1
Periodic Maintenance Instructions
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(s). 2) Disconnect negative (-) battery cable from battery.
Maintenance Schedule
These required maintenance procedures should be performed at the frequency stated in the table. They should
also be included as part of any seasonal tune-up.
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. On
Electronic Fuel Injected (EFI) engines, avoid
spraying water at the wiring harness or any of
the electrical components.
2. Change the oil and oil filter while the engine is
still warm from operation. See “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 to 3 minutes to get stabilized fuel
into the rest of the system. Close the fuel shut-off
valve when the unit is being stored or
transported.
To empty the system, run the engine until the
tank and the system are empty.
4. Remove the spark plugs and add one tablespoon
of engine oil into each spark plug hole. Install the
spark plugs, but do not connect the plug leads.
Crank the engine two or three revolutions.
5. On equipment with an EFI engine, disconnect the
battery or use a battery minder to keep the
battery charged during storage.
6. Store the engine in a clean, dry place.
• Replace fuel filter
1
(EFI engines). Section 5B
Daily or Before
Starting Engine
Maintenance Required Frequency
• Fill fuel tank Section 5
• Check oil level. Section 6
• Check air cleaner for dirty
1
, loose, or damaged parts. Section 4
• Check air intake and cooling areas, clean as necessary
1
. Section 4
• Service precleaner element
1
. Section 4 Every 25 Hours
• Replace air cleaner element
1
. Section 4
• Change oil. (More frequently under severe conditions.) Section 6
• Remove cooling shrouds and clean cooling areas
1,3
. Section 4
• Check oil cooler fins, clean as necessary (if equipped). Section 6
• Check spark plug condition and gap. Section 8
• Change oil filter. Section 6
• Change fuel filter (carbureted engines). Section 5
Annually or
Every 500 Hours
• Have bendix starter drive serviced
2
. Section 8
• Have solenoid shift starter disassembled and cleaned
2
. Section 8
Every 100 Hours
Every 200 Hours
Every 1500 Hours
• Have crankshaft splines lubricated
2
. Section 2 Every 500 Hours
Every 250 Hours • Replace heavy-duty air cleaner element and check inner element
1
. Section 4
¹Perform these maintenance procedures more frequently under extremely dusty, dirty conditions.
²Only requried for Denso starters. Not necessary on Delco starters. Have a Kohler Engine Service Dealer perform this service.
³Cleanout Kits 25 755 20-S (black) or 25 755 21-S (gold) allow cooling areas to be cleaned without removing shrouds.
Refer to:

1.6
Section 1
Safety and General Information
Figure 1-4. Typical Engine Dimensions CH Series with Standard Flat Air Cleaner.
Dimensions in millimeters.
Inch equivalents shown in [ ].

1.7
Section 1
Safety and General Information
1
Figure 1-5. Typical Engine Dimensions CH EFI Series with Heavy-Duty Air Cleaner.
Dimensions in millimeters.
Inch equivalents shown in [ ].

1.8
Section 1
Safety and General Information
General Specifications¹
Power (@ 3600 RPM, exceeds Society of Automotive Engineers-Small Engine Test Code J1940.)
CH18 ........................................................................................................................................ 13.4 kW (18 HP)
CH20 ........................................................................................................................................ 14.9 kW (20 HP)
CH22 ........................................................................................................................................ 16.4 kW (22 HP)
CH23 ........................................................................................................................................ 17.2 kW (23 HP)
CH25, CH730 .......................................................................................................................... 18.6 kW (25 HP)
CH26 ........................................................................................................................................ 19.4 kW (26 HP)
CH740 ...................................................................................................................................... 20.1 kW (27 HP)
CH745 ...................................................................................................................................... 20.9 kW (28 HP)
CH750 ...................................................................................................................................... 22.3 kW (30 HP)
Peak Torque
CH18 @ 2200 RPM ................................................................................................................. 43.6 N·m (32.2 ft. lb.)
CH20 @ 2400 RPM ................................................................................................................. 44.3 N·m (32.7 ft. lb.)
CH22 @ 2400 RPM ................................................................................................................. 49.1 N·m (36.2 ft. lb.)
CH23 @ 2400 RPM ................................................................................................................. 54.1 N·m (37.9 ft. lb.)
CH25 @ 2200 RPM ................................................................................................................. 54.0 N·m (39.5 ft. lb.)
CH730 @ 2400 RPM ............................................................................................................... 55.4 N·m (40.9 ft. lb.)
CH26 @ 2800 RPM ................................................................................................................. 54.2 N·m (40.0 ft. lb.)
CH740 @ 2400 RPM ............................................................................................................... 57.3 N·m (42.3 ft. lb.)
CH745 @ 2600 RPM ............................................................................................................... 57.9 N·m (42.7 ft. lb.)
CH750 @ 2400 RPM ............................................................................................................... 64.4 N·m (47.5 ft. lb.)
Bore
CH18, CH20, CH22 (624 cc) .................................................................................................. 77 mm (3.03 in.)
CH22/23 (674 cc) .................................................................................................................... 80 mm (3.15 in.)
CH25, CH26, CH730-750 ....................................................................................................... 83 mm (3.27 in.)
Stroke
CH18-745 ................................................................................................................................ 67 mm (2.64 in.)
CH750 ...................................................................................................................................... 69 mm (2.7 in.)
Displacement
CH18, CH20, CH22 (624 cc) .................................................................................................. 624 cc (38 cu. in.)
CH22/23 (674 cc) .................................................................................................................... 674 cc (41 cu. in.)
CH25, CH26, CH730-745 ....................................................................................................... 725 cc (44 cu. in.)
CH750 ...................................................................................................................................... 755 cc (46 cu. in.)
Compression Ratio
CH18, CH20, CH22/23 ........................................................................................................... 8.5:1
CH25, CH26, CH730-745 ....................................................................................................... 9.0:1
CH750 ...................................................................................................................................... 9.4:1
Dry Weight
CH18, CH20, CH22/23 ........................................................................................................... 41 kg (90 lb.)
CH25, CH26, CH730-745 ....................................................................................................... 43 kg (94 lb.)
CH750 ...................................................................................................................................... 48 kg (105 lb.)
Oil Capacity (w/filter) - approximate,
determined by oil filter and oil cooler used ............................................................................. 1.6-1.8 L (1.7-1.9 U.S. qt.)
¹Values are in Metric units. Values in parentheses are English equivalents. Lubricate threads with engine oil
prior to assembly.
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