Kohler CH640, CH740, CH730 Owner's Manual

24 590 48 Rev. --

KohlerEngines.com

Owner's Manual

IMPORTANT:

Read all safety precautions and instructions carefully before operating
equipment. Refer to operating instruction of equipment that this engine powers.

Ensure engine is stopped and level before performing any maintenance or
service.

Warranty coverage as outlined in the warranty card and on KohlerEngines.
com. Please review carefully as it provides your specifi c rights and obligations.

To maintain compliance with applicable emission regulations, exhaust system
backpressure may not exceed limits which can be found on KohlerEngines.
com. Search by Model No., then select Specs tab.

Kohler Engines has published CO2 values on KohlerEngines.com website.

Record engine information to reference when ordering parts or obtaining warranty coverage.

Engine Model

Specifi cation

Serial Number

Purchase Date

CH640, CH730, CH740

Liquefi ed Petroleum Gas (LPG) or LPG/Natural Gas (NG) Fueled

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Safety Precautions

WARNING: A hazard that could result in death, serious injury, or substantial property damage.

CAUTION: A hazard that could result in minor personal injury or property damage.

NOTE: is used to notify people of important installation, operation, or maintenance information.

WARNING

Explosive Fuel
can cause fi res
and severe
burns.

If a gaseous
odor is detected,
ventilate area
and contact
an authorized
service
technician.

LPG is extremely fl ammable
and is heavier than air and
tends to settle in low areas
where a spark or fl ame
could ignite gas. Do not
start or operate this engine
in a poorly ventilated area
where leaking gas could
accumulate and endanger
safety of persons in area.

NG is extremely fl ammable,
is lighter than air, and rises.
Do not start or operate this
engine in a poorly ventilated
area where leaking gas
could accumulate and
endanger safety of persons
in area.

To ensure personal
safety, installation and
repair of LPG/NG fuel
supply systems must
be performed only by
qualifi ed LPG/NG system
technicians. Improperly
installed and maintained
LPG/NG equipment could
cause fuel supply system
or other components to
malfunction, causing gas
leaks.

Observe federal, state
and local laws governing
LPG/NG fuel, storage, and
systems.

WARNING

Hot Parts can
cause severe
burns.

Do not touch
engine while
operating or just
after stopping.

Never operate engine with
heat shields or guards
removed.

WARNING

Accidental
Starts can cause
severe injury or
death.

Disconnect and
ground spark
plug lead(s)
before servicing.

Before working on engine or
equipment, disable engine
as follows: 1) Disconnect
spark plug lead(s). 2)
Disconnect negative (–)
battery cable from battery.

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

WARNING

Carbon
Monoxide can
cause severe
nausea, fainting
or death.

Avoid inhaling
exhaust fumes.
Never run
engine indoors
or in enclosed
spaces.

Engine exhaust gases
contain poisonous carbon
monoxide. Carbon
monoxide is odorless,
colorless, and can cause
death if inhaled.

CAUTION

Electrical Shock
can cause injury.

Do not touch
wires while
engine is
running.

WARNING

Rotating Parts
can cause
severe injury.

Stay away while
engine is in
operation.

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

WARNING: This product can expose you to chemicals

including carbon monoxide and benzene, which are known
to the State of California to cause cancer and birth defects
or other reproductive harm. For more information go to
www.P65Warnings.ca.gov.

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Pre-Start Checklist

1. Check oil level. Add oil if low. Do not overfi ll.

2. Check fuel gauge (if equipped). If LPG tank is low, have it refi lled. Check fuel system
components and lines for leaks.

3. Check and clean cooling areas, air intake areas and external surfaces of engine (particularly
after storage).

4. Check that air cleaner components and all shrouds, equipment covers, and guards are in place
and securely fastened.

5. Check spark arrestor (if equipped).

A

P

O

A Oil Fill B Vaporizer C LPG Regulator D Debris Screen

E Dipstick F Oil Filter G Oil Drain Plug H

Air Cleaner

Base

I Paper Element J Precleaner K Rubber Seal L Element Cover

M Wing Nut N

Air Cleaner

Cover

O

Air Cleaner

Knob

P

Low-Profi le Air

Cleaner

Visit KohlerEngines.com for service parts information and purchasing options.

M

K

L

J

I

H

N

B

C

B

C

G

E

D

F

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Starting

WARNING

Carbon Monoxide can cause
severe nausea, fainting or death.

Avoid inhaling exhaust fumes.
Never run engine indoors or in
enclosed spaces.

Engine exhaust gases contain poisonous
carbon monoxide. Carbon monoxide is
odorless, colorless, and can cause death if
inhaled.

WARNING

Rotating Parts can cause severe
injury.

Stay away while engine is in
operation.

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

NOTE: Do not crank engine continuously for

more than 10 seconds. Allow a 60
second cool down period between
starting attempts. Failure to follow
these guidelines can burn out starter
motor.

NOTE: Upon start-up, a metallic ticking may

occur. Run engine for 5 minutes. If
noise continues, run engine at mid
throttle for 20 minutes. If noise persists,
take engine to your local Kohler
authorized dealer.

NOTE: If starter is engaged while fl ywheel is

rotating, starter pinion and fl ywheel ring
gear may clash resulting in damage to
starter.

1. Place throttle control (if equipped) into idle

position. Place choke control (if equipped)
into ON position.

2. Slowly turn fuel valve on LPG (propane) tank

or NG line (if equipped) to full open position.

3. Turn key switch to START position. Release

switch as soon as engine starts. If starter
does not turn engine over, shut off key switch
immediately. Do not make further attempts to
start engine until condition is corrected. Do
not jump start. See your Kohler authorized
dealer for trouble analysis.

Cold Weather Starting Hints

1. Use proper oil for temperature expected.

2. Disengage all possible external loads.

Stopping

1. If possible, remove load by disengaging all
PTO driven attachments.

2. Turn fuel valve to full closed position and
allow engine to continue running until it runs
out of fuel. Turn key switch to OFF position.
Switching off key switch prior to allowing
engine to run out of fuel may create a
backfi re.

Angle of Operation

Refer to operating instructions of equipment
this engine powers. Do not operate this engine
exceeding maximum angle of operation; see
specifi cation table. Engine damage could result
from insuffi cient lubrication.

Engine Speed

NOTE: Do not tamper with governor setting to

increase maximum engine speed.
Overspeed is hazardous and will void
warranty.

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Maintenance Instructions

WARNING

Before working on engine or equipment, disable
engine as follows: 1) Disconnect spark plug
lead(s). 2) Disconnect negative (–) battery cable
from battery.

Accidental Starts can cause
severe injury or death.

Disconnect and ground spark
plug lead(s) before servicing.

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 dealer found at KohlerEngines.com or 1-800-544-2444 (U.S. and Canada).

For safety and health reasons, many states require special licensing or certifi cation for servicing
LPG fuel systems. Check local and state regulations before choosing a repair establishment to
perform fuel system repairs.

Maintenance Schedule

Every 25 Hours

1

● Service precleaner element.
Every 100 Hours

1

● Check oil cooler fi ns, clean as necessary (if equipped).

● Change oil.

● Replace air cleaner element.

● Remove cooling shrouds and clean cooling areas.
Every 200 Hours

1

● Change oil fi lter.
Every 500 Hours or Annually1 (whichever comes first)

● Check all lines (high pressure/vacuum) including fi ttings for leaks.

● Drain regulator of accumulated fuel deposits.

● Replace spark plugs and set gap.

Every 500 Hours or Annually

1,2

(whichever comes first)

● Have lock-off /fi lter serviced.

● Have combustion deposits removed if using non-synthetic oil.
Every 1500 Hours

1,2

● Have regulator disassembled, cleaned, and reset.

● Have vaporizer disassembled, cleaned, and serviced.

1

Perform these procedures more frequently under severe, dusty, dirty conditions.

2

Must be performed by a Kohler authorized dealer or qualifi ed LPG personnel only.

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Oil Recommendations

Synthetic oil is recommended for use in
LPG/NG fueled engines. Non-synthetic oil must
be low ash* rated oil. Oils (including synthetic)
must meet API (American Petroleum Institute)
service class SG, SH, SJ, or SL. Select
viscosity based on air temperature at time of
operation as shown in table below.

*Low ash is defi ned as less than 1% sulfated
ash.

°F

-20

020324060

50 80 100

°C

-30 -20

-10 0

10 20 30

40

5W-30

10W-30

SAE 30

Check Oil Level

NOTE: To prevent extensive engine wear or

damage, never run engine with oil level
below or above operating range
indicator on dipstick.

Ensure engine is cool. Clean oil fi ll/dipstick
areas of any debris.

1. Remove dipstick; wipe oil off .

a. Press-in cap: reinsert dipstick into tube;

press completely down.

or

b. Thread-on cap: reinsert dipstick into

tube; rest cap on tube, do not thread cap
onto tube.

2. Remove dipstick; check oil level. Level
should be at top of indicator on dipstick.

3. If oil is low on indicator, add oil up to top of
indicator mark.

4. Reinstall dipstick and tighten securely.

Change Oil and Filter

Change oil while engine is warm.

1. Clean area around oil fi ll cap/dipstick, drain
plug/oil drain valve.

a. Remove drain plug and oil fi ll cap/

dipstick. Allow oil to drain completely.

or

b. Open oil drain valve cap; if needed,

attach a length of 1/2 in. I.D. hose to
direct oil into appropriate container; twist
valve drain body counterclockwise and
pull. Remove dipstick. Allow oil to drain
completely.

2. Clean area around oil fi lter. Place a container
under fi lter to catch any oil and remove fi lter.
Wipe off mounting surface.

a. Reinstall drain plug. Torque to 10 ft. lb.

(13.6 N·m).

or

b. Close oil drain valve body, remove hose

(if used), and replace cap.

3. Place new fi lter in shallow pan with open end
up. Fill with new oil until oil reaches bottom of
threads. Allow 2 minutes for oil to be
absorbed by fi lter material.

4. Apply a thin fi lm of clean oil to rubber gasket
on new fi lter.

5. Refer to instructions on oil fi lter for proper
installation.

6. Fill crankcase with new oil. Level should be
at top of indicator on dipstick.

7. Reinstall oil fi ll cap/dipstick and tighten
securely.

8. Start engine; check for oil leaks. Stop engine;
correct leaks. Recheck oil level.

9. Dispose of used oil and fi lter in accordance
with local ordinances.

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Oil Sentry™ (if equipped)

This switch is designed to prevent engine
from starting in a low oil or no oil condition. 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.

Fuel Recommendations

WARNING

Explosive Fuel can cause fi res
and severe burns.

If a gaseous odor is detected,
ventilate area and contact an
authorized service technician.

LPG is extremely fl ammable and is heavier
than air and tends to settle in low areas
where a spark or fl ame could ignite gas. Do
not start or operate this engine in a poorly
ventilated area where leaking gas could
accumulate and endanger safety of persons
in area.

NG is extremely fl ammable, is lighter than air,
and rises. Do not start or operate this engine
in a poorly ventilated area where leaking gas
could accumulate and endanger safety of
persons in area.

To ensure personal safety, installation and
repair of LPG/NG fuel supply systems must
be performed only by qualifi ed LPG/NG
system technicians. Improperly installed and
maintained LPG/NG equipment could cause
fuel supply system or other components to
malfunction, causing gas leaks.

Observe federal, state and local laws
governing LPG/NG fuel, storage, and
systems.

This engine is certifi ed to operate on LPG or
LPG/NG.

LPG Engines

LPG from an appropriate LPG fuel tank
(supplied separately) is required to operate this
engine.

NG Engines

NG from an approved system or source of
supply can be used to operate this engine.

Fuel Conversion

NOTE: When switching from NG to LPG fuel

or LPG to NG fuel, battery must be
temporarily disconnected for safety and
to reset system.

Some engines are equipped to convert between
LPG and NG. Models with fi tting and jet should
follow these instructions for conversion. Other
metering valves should be installed following
instructions given by equipment it powers.
Shut off fuel supply before any servicing is
performed.

LPG Operation

Installation of jet in regulator fi tting is required
for LPG operation.

Switching from NG to LPG

Remove fuel inlet hose. Inspect internal threads
of regulator fi tting to ensure they are clean and
dry. Install jet into fuel elbow orifi ce for LPG
operation. Reconnect and fully tighten fuel inlet
hose.

Outlet pressure should be checked and if
required, set at secondary regulator to 4.0 to

5.0 psi by qualifi ed personnel.

NG Operation

Removal of jet from regulator fi tting is required
for NG operation.

Switching from LPG to NG

Remove LPG fuel jet from regulator fi tting.
Disconnect hose, remove jet from orifi ce, and
reconnect hose.

Recommended fuel inlet pressure for NG
systems is 11 in. water (engine off ). Reduced
pressure could result in hard starting.

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LPG Regulator

In compliance with government emission
standards, regulator is preset at factory to
provide proper supply of fuel. No adjustment or
resetting of regulator is to be made. All service
relating to regulator must be performed by
a Kohler authorized dealer or qualifi ed LPG
personnel only.

Over time, fuel deposits can accumulate
inside regulator. Removing these deposits is
recommended (Nikki regulators only). Follow
steps below to drain Nikki Regulators.

1. Turn fuel supply valve off , run engine out of
fuel, and turn off ignition switch.

2. Disconnect and ground spark plug leads.

3. Remove 1/8" pipe plug from bottom of
regulator. Remove any accumulated
deposits.

4. Reinstall plug using Tefl on

®

pipe sealant (not
Te fl on® tape) on threads and tighten securely.
If required, a replacement plug can be found
at KohlerEngines.com.

Lock-Off /Filter Assembly

Lock-Off /Filter Assembly opens, closes, and
fi lters liquid fuel fl ow from supply tank before
reaching vaporizer.

Vaporizer

Vaporizer changes Liquefi ed Petroleum (LPG)
from supply tank to a gaseous/vapor state.

Spark Plugs

CAUTION

Electrical Shock can cause injury.

Do not touch wires while engine
is running.

Clean out spark plug recess. Remove plug and
replace.

1. Check gap using wire feeler gauge. Adjust
gap, see specifi cation table for adjustment.

2. Install plug into cylinder head.

3. Torque plug to 20 ft. lb. (27 N·m).

Air Cleaner

NOTE: Operating engine with loose or

damaged air cleaner components
could cause premature wear and
failure. Replace all bent or damaged
components.

NOTE: Paper element cannot be blown out

with compressed air.

Loosen knob and remove air cleaner cover.

Precleaner:

1. Remove precleaner from paper element.

2. Replace or wash precleaner in warm water
with detergent. Rinse and allow to air dry.

3. Saturate precleaner with new engine oil;
squeeze out excess oil.

4. Reinstall precleaner over paper element.

Paper Element:

1. Clean area around element. Remove wing
nut, element cover, and paper element with
precleaner.

2. Separate precleaner from element; service
precleaner and replace paper element.

3. Check condition of rubber seal and replace if
necessary.

4. Install new paper element on base; install
precleaner over paper element; reinstall
element cover and secure with wing nut.

Reinstall air cleaner cover and secure with
knob.

Breather Tube (if equipped)

Ensure end of breather tube is properly
connected.

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Oil Cooler (if equipped)

1. Clean fi ns with a brush or compressed air.

2. Remove two screws securing oil cooler, and
tilt to clean back side.

3. Reinstall oil cooler.

Air Cooling

WARNING

Hot Parts can cause severe
burns.

Do not touch engine while
operating or just after stopping.

Never operate engine with heat shields or
guards removed.

Proper cooling is essential. To prevent over
heating, clean screens, cooling fi ns, and other
external surfaces of engine. Avoid spraying
water at wiring harness or any electrical
components. See Maintenance Schedule.

Repairs/Service Parts

We recommend that you use a Kohler
authorized dealer for all maintenance,
service, and replacement parts for engine.
To fi nd a Kohler authorized dealer visit
KohlerEngines.com or call 1-800-544-2444
(U.S. and Canada).

Leakage Check/Testing

With fuel valve fully opened, engine not
running, turn key switch ON. Check all fuel
system connections and lines for leaks using
soapy water. Any leakage must be corrected
before restarting engine. Have service
performed by a Kohler authorized dealer or
qualifi ed LPG/NG personnel only.

Storage

If engine will be out of service for 2 months or
more follow procedure below.

1. Change oil while engine is still warm from
operation. Remove spark plug(s) and pour
about 1 oz. of engine oil into cylinder(s).
Replace spark plug(s) and crank engine
slowly to distribute oil.

2. Disconnect negative (-) battery cable.

3. Separate LPG tank from unit and store
separately in an area designated for safe
LPG tank storage.

4. Store engine in a clean, dry place.

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Troubleshooting

Do not attempt to service or replace major engine components, or any items that require special timing or adjustment procedures. This work

should be performed by a Kohler authorized dealer.

Possible Cause

Problem

No Fuel

Improper

Fuel

Dirt In

Fuel Line

Dirty/

Restricted

Lock-off

Fuel Filter

Dirty

Debris

Screen

Incorrect

Oil Level

Engine

Overloaded

Dirty Air

Cleaner

Faulty

Spark

Plug

Dirty/

Restricted

Regulator

Will Not Start

●●●●●●●●●

Hard Starting

●●● ● ● ● ● ●● ●

Stops Suddenly

●●●●●●● ●

Lacks Power

●● ● ● ● ● ●● ●

Operates Erratically

●● ● ● ● ●● ●

Knocks or Pings

●●● ●●●

Skips or Misfi res

●● ● ● ●● ●

Backfi res

●● ●● ●

Overheats

●● ● ● ● ● ● ●

High Fuel Consumption

●●

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Engine Specifi cations

Model Bore Stroke Displacement

Oil Capacity

(Refi ll)

Spark Plug

Gap

Maximum Angle

of Operation

(@ full oil level)*

CH640

3.03 in.

(77 mm)

2.64 in.

(67 mm)

38 cu. in.

(624 cc)

1.7-1.9 U.S. qt.
(1.6-1.8 L)

0.020 in.

(0.51 mm)

25°

CH730

3.27 in.

(83 mm)

44 cu. in.

(725 cc)

0.030 in.

(0.76 mm)

CH740

*Exceeding maximum angle of operation may cause engine damage from insuffi cient lubrication.

Additional specifi cation information can be found in service manual at KohlerEngines.com.

Any and all horsepower (hp) references by Kohler are Certifi ed Power Ratings and per SAE J1940
& J1995 hp standards. Details on Certifi ed Power Ratings can be found at KohlerEngines.com.

Emission Control System

Exhaust Emission Control System for gaseous fuel models CH640, CH730, and CH740 is EM for
U.S. EPA, California, and Europe.

NOTE: Tampering with the engine and its emission control system voids the EPA Certifi cate of

Conformity, ARB Executive Order, and EU type-approval.

24 590 48 Rev. --KohlerEngines.com

© 2018 by Kohler Co. All rights reserved.