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Kohler CH740 4-Cycle Engine

Name: Kohler CH740 4-Cycle Engine
Brand: Kohler

The Kohler CH740 4-Cycle is a 0.72 L 2-cylinder naturally aspirated engine rated at 3600 rpm, producing up to 17.6 kW. It powers generator sets from Kohler, including the 12RES and 6VSG. It holds 1.9 L (0.5 gal) of oil.

Also known as: Kohler CH740 4-Cycle

0.725 L

Displacement

Cylinders

3600 rpm

Rated speed

17 kW

Gross power

On this pageSpecs Generator sets Maintenance FAQ Service intervals Torque & specs Fluids Fault codes Procedures Wiring

Engine specifications

Oil capacity	1.9 L
Displacement	0.725 L
Cylinders	2
Aspiration	Naturally aspirated
Rated speed	3600 rpm
Gross power	17 kW

Generator sets powered by this engine

Kohler 12RES Kohler 6VSG

How to read your Kohler engine serial & model number →

Common problems

Gas fuel leaks can cause an explosion.
Fix: Check the LP vapor gas or natural gas fuel system for leakage by using a soap and water solution with the fuel system test pressurized to 6–8 ounces per square inch (10–14 inches water column). Do not use a soap solution containing either ammonia or chlorine because both prevent bubble formation. A successful test depends on the ability of the solution to bubble.
Upgradeable application software Undervoltage
Undervoltage shutdown UU
Cause: Shutdown occurs if the voltage falls below 80% of the nominal system voltage for more than 10 seconds.
Fix: Reduce the load and restart the generator set. Contact an authorized distributor/dealer for service if problem continues.
Underfrequency shutdown UF
Cause: Shutdown occurs if the governed frequency falls below 54 Hz for more than 5 seconds. Shutdown also occurs if the governed frequency falls below 56.5 Hz for more than 60 seconds. This function becomes active 10 seconds after engine start. (10 second inhibit).
Fix: Reduce the load and restart the generator set. Contact an authorized distributor/dealer for service if problem continues.
The generator set does not crank.
Cause: Battery weak or dead, Battery charger fuse blown, Battery connections reversed or poor, Controller fuse (F3) blown, Relay interface board fuse (F2) blown
Fix: Check power to the battery charger. Recharge or replace the battery. Replace the fuse. Contact an authorized distributor/dealer for service if fuse blows repeatedly. Check the connections. Replace the fuse. Contact an authorized distributor/dealer for service if fuse blows repeatedly.
The generator set cranks but does not start, starts hard, lacks power, or operates erratically.
Cause: Air cleaner clogged
Fix: Clean and/or replace the air cleaner. Battery weak or dead Check power to the battery charger. Recharge or replace the battery. Battery connection poor Clean and tighten the battery connections. Spark plug wire connection loose Check the spark plug wires. Low oil pressure shutdown Check the oil level. Fuel pressure insufficient Check the fuel supply and valves. Engine malfunction Contact an authorized distributor/dealer.
The generator set also shuts down on OC if no engine rotation is sensed during cranking. Shuts down 3 seconds after the fault is detected. Locked rotor
Stops suddenly
Cause: Fault shutdown
Fix: Check for a fault shutdown code on the controller’s LED display. Correct the fault and then move the generator set master switch to OFF/RESET to reset the controller.
Stator problem
Fix: Check voltage and continuity.
Shutdown occurs when the governed frequency falls 1 Hz below the system’s frequency setpoint for more than 1 second. UF
Fix: Reduce the load and restart the generator set. Contact an authorized distributor/dealer for service if problem continues.
Shutdown occurs when the governed frequency exceeds 110% of the system’s frequency setpoint for more than 1 second. This protective becomes active 30 seconds after engine start. OF
Fix: Contact an authorized distributor/dealer for service if problem continues.
Shutdown occurs if the voltage falls below 80% of the voltage regulator setpoint for more than 1 second. This protective becomes active 30 seconds after engine start. UU
Fix: Reduce the load and restart the generator set. Contact an authorized distributor/dealer for service if problem continues.
Shutdown occurs if the voltage exceeds 120% of the voltage regulator setpoint for more than 1 second. OU
Fix: Contact an authorized distributor/dealer for service if problem continues.
Shutdown occurs if the engine speed exceeds 115% of the normal running speed for more than 1 second. OS
Fix: Contact an authorized distributor/dealer for service if problem continues.
Shutdown occurs if the engine coolant temperature exceeds the maximum temperature for more than 5 seconds. This protective becomes active after the engine reaches the crank disconnect speed. HE
Fix: Check for blocked air inlets and exhaust outlets.

Compiled from service & troubleshooting documentation across every generator set that uses the Kohler CH740 4-Cycle.

Maintenance schedule

Item	Spec	Capacity	Part #
Air filter	Dry		—
Fuel filter			—
Oil filter	Cartridge		—
Battery	Group size 51, CCA 500		—
Belt			—
Coolant			—
Oil		1.9 L	—
Spark plug			—

Pooled from every document that names this exact engine — confirm the interval and part number against your unit's serial number.

Service intervals

Item	Action	Hours	Months	Notes
Oil level	Check	8 hr		First service — Lubrication; 8 hours or before use
Air cleaner and precleaner	Clean	100 hr	12 mo	Yearly or 100 Hrs.; service more often in dusty areas
Air cleaner and precleaner (8.5/12RES)	Replace	100 hr	12 mo	Yearly or 100 hours; replace as necessary
Air cleaner and precleaner service	Clean	100 hr	12 mo	Yearly or 100 hr.; service more frequently in dusty areas
Air cleaner and precleaner service	Replace	100 hr	12 mo	12 kW models; Yearly or 100 hours; replace as necessary
Air cleaner and precleaner service (8.5/12 kW)	Replace	100 hr		Yearly or 100 hours; service more frequently under dusty/dirty conditions
Air cleaner service	Replace	300 hr	12 mo	Engine and Mounting; Yearly or 100 hours; replace as necessary (R)
Change oil	Replace	100 hr	12 mo	Yearly or 100 hr.
Crankcase oil	Change	100 hr	12 mo	Yearly or 100 Hrs.
Engine oil	Change	150 hr	12 mo	Lubrication; Yearly or 100 hours
Oil cooler	Clean	100 hr	12 mo	Yearly or 100 hours; 17/18 kW models
Oil cooler	Inspect	100 hr		Yearly or 100 hours (17/18 kW models)
Oil cooler (17/18RES)	Clean	100 hr	12 mo	Yearly or 100 hours; inspect and clean
Air cleaner service	Clean	150 hr		Yearly or hours shown; 17/18 kW models
Air cleaner service (17/18 kW)	Replace	150 hr		Yearly or 150/300 hours
Change oil	Change	150 hr	12 mo	Yearly or 150 hours (17/18 kW models)
Engine oil (17/18RES)	Change	150 hr	12 mo	Yearly or 150 hours
Oil	Change	150 hr		Yearly or 150 hours; 17/18 kW models
Oil filter (17/18RES)	Replace	150 hr	12 mo	Yearly or 150 hours
Spark plugs	Clean	150 hr		Yearly or hours shown; 17/18 kW models
Spark plugs (17/18 kW)	Replace	150 hr		Yearly or 150/300 hours
Oil filter	Replace	200 hr	12 mo	Yearly or 200 hours; 8.5/12 kW models
Oil filter(s)	Replace	200 hr	12 mo	Yearly or 200 Hrs.
Replace filter	Replace	200 hr	12 mo	Yearly or 200 hours
Replace filter (oil filter)	Replace	200 hr		Yearly or 200 hours (8.5/12 kW models)
Replace filter(s)	Replace	200 hr	12 mo	Yearly or 200 hr.
Air cleaner service	Change	300 hr		Yearly or hours shown; 17/18 kW models
Spark plugs	Check	300 hr	12 mo	Yearly or 300 hours; 8.5/12 kW models
Spark plugs	Replace	500 hr	12 mo	Yearly or hours shown; 17/18 kW models
Spark plugs (8.5/12 kW)	Replace	300 hr		Yearly or 300 hours
Spark plugs (8.5/12RES)	Check	300 hr	12 mo	Yearly or 300 hours
Crankcase breather	Change	500 hr	12 mo	Lubrication; Yearly or 500 hours
Crankcase breather hose	Check	500 hr	12 mo	Yearly or 500 hours; 8.5/12 kW models
Crankcase breather hose	Clean	500 hr	12 mo
Crankcase breather hose	Other	500 hr	12 mo	Yearly or 500 hr.; follow engine manufacturer's maintenance manual
Replace spark plugs	Replace	500 hr
Replace stepper motor coupling and bushing	Replace	500 hr		authorized distributor/dealer only
Resistance readings of windings with insulation tester (Megger)	Test	500 hr	36 mo	3 yr.; with SCR assembly or rectifier and load leads disconnected
Stepper motor coupling and bushing	Replace	500 hr	36 mo	Engine and Mounting; 500 hours
Wire-cable insulation breakdown	Inspect	500 hr	36 mo	3 Years or 500 Hrs.

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Service specifications

Type	Item	Value	Unit	Condition
Clearance	Clearance at exhaust end	4	ft
Clearance	Clearance to combustible wall	5	ft
Clearance	Clearance to non-combustible wall (minimum)	18	in
Clearance	Clearance to non-combustible wall (recommended)	3	ft
Clearance	Distance from exhaust end of set to furnace and other similar intakes	10	ft
Clearance	Distance from exhaust end of set to nearest structure opening (window, vent, door)	5	ft
Clearance	Gravel base thickness (with weed barrier)	3	in
Clearance	Minimum distance of plants, shrubs, or combustibles from air intake	18	in
Clearance	Recommended distance from structure (NFPA 37, combustible material)	5	ft
Gap	Magnetic pickup air gap	0.5	mm (0.020 in.)
Gap	Spark Plug Gap 12/17/18RES	0.76	mm (0.030 in.)
Gap	Spark Plug Gap 8.5kW	0.51	mm (0.020 in.)
Gap	Spark plug gap	0.51	mm (0.02 in.)
Gap	Spark plug gap	0.7--0.8	mm (0.028--0.030 in.)
Gap	Spark plug gap	0.76	mm (0.030 in.)
Gap	Spark plug gap	0.76 mm (0.030 in.)	mm
Gap	Spark plug gap	0.8--0.9	mm (0.03--0.04 in.)
Gap	Spark plug gap	0.89	mm (0.035 in.)
Gap	Spark plug gap	0.9--1.0	mm (0.036--0.04 in.)
Other	Anchor bolt size	3/8	in	4 places, high wind 150 mph mounting detail
Other	Battery charger output	6	amp
Other	Battery charger power requirement (max.)	192	watts	max.
Other	Battery electrolyte specific gravity (full charge)	1.260		electrolyte at 26.7 C (80 F)
Other	Battery minimum cold cranking amps	525	CCA	at 0F
Other	Battery specific gravity (charge threshold)	1.215		electrolyte at 26.7 C (80 F)
Other	Battery specific gravity variation (charge threshold)	0.01		cell-to-cell variation
Other	Battery wrap length	1067 (42)	mm (in.)
Other	Battery wrap length	864 (34)	mm (in.)
Other	Below ground level (fuel line depth)	76-102 [3.0-4.0]	mm [in]
Other	Brush length, new	19.05	mm (0.75 in.)	new
Other	Carburetor heater power requirement (max.)	38	watts	max., not included on all models
Other	Combustion air requirement	1.1	m3/min
Other	Combustion air requirement (60 Hz)	1.1 (39.2)	m3/min. (cfm)	60 Hz
Other	Combustion air requirement (60 Hz)	1.62 (57.3)	m3/min. (cfm)	60 Hz
Other	Compression ratio	8.5:1
Other	Compression ratio	9.0:1
Other	Cooling air requirement	26.9	m3/min
Other	Cooling air requirement (60 Hz)	26.9 (950)	m3/min. (cfm)	60 Hz
Other	Cooling air requirement (60 Hz)	28.0 (989)	m3/min. (cfm)	60 Hz
Other	Crank cycle	3 attempts of 15 seconds cranking and 15 seconds rest	seconds
Other	Engine oil capacity	1.9	L (2.0 qt.)
Other	Engine oil capacity	1.9 L (2.0 qt.)	L
Other	Engine oil capacity	2.8	L (3.0 qt.) approximately
Other	Exhaust flow at rated kW	3.8	m3/min	rated kW
Other	Exhaust flow at rated kW	3.8 (135)	m3/min (cfm)	at rated kW
Other	Exhaust flow at rated kW	5.3 (187)	m3/min (cfm)	at rated kW
Other	Fuel flow rate, LP vapor	203000	Btu/hr.
Other	Fuel flow rate, LP vapor	280000	Btu/hr.
Other	Fuel flow rate, natural gas	193000	Btu/hr.
Other	Fuel flow rate, natural gas	242000	Btu/hr.
Other	Fuel supply inlet	1/2	NPT
Other	Fuel system leak test pressure	6-8 ounces per square inch (10-14 inches water column)	oz/in²	LPG vapor or natural gas system
Other	Gas flow rate required for the generator set	193,000	Btu/hr.
Other	Heater wrap rating	50	Watts
Other	Heater wrap rating	65	Watts
Other	Insulation resistance indicating good stator/rotor	500	kOhms (1/2 megohm) or higher
Other	Low oil pressure shutdown activation	30 seconds after engine reaches crank disconnect speed	seconds	30 second inhibit
Other	Maximum natural gas pipe length, 1 1/4 in. NPT	68.6	m	1 1/4 in. NPT
Other	Maximum natural gas pipe length, 1 in. NPT	30	m	1 in. NPT
Other	Maximum natural gas pipe length, 3/4 in. NPT	9.2	m	3/4 in. NPT

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Recommended fluids

Fluid	Grade	Standard	Ambient	Capacity	Notes
Engine oil	5W-30	API Service Class SG, SH, or SJ synthetic		2.8 L	18 kW models; approximately 2.8 L (3.0 qt.)
Engine oil	Recommended oil			1.9 L	With filter
Engine oil	Synthetic	API Service Class SG or higher			Use synthetic oil, API Service Class SG or higher
Engine oil	Synthetic oil, API Service Class SG or higher	API SG or higher		1.9 L (2.0 qt.)	8.5RES capacity with filter; see engine oil selection chart for viscosity (5W-20, 5W-30, 10W-30)
Engine oil	10W-30; 5W-20, 5W-30	API Service Class SG, SH, or SJ synthetic	-30°C to 40°C	1.9 L	12 kW models; select viscosity based on air temperature expected before next oil change
Engine oil	5W-20, 5W-30	API Service Class SG or higher, synthetic	-30°C to 10°C		Engine Oil Selection chart; use synthetic oil
Engine oil	Kohler PRO 10W-50 synthetic		-29°C to 49°C	1.9 L	Extends oil change intervals to 300 hours
Engine oil	10W-30	API Service Class SG or higher, synthetic	-20°C to 40°C		Engine Oil Selection chart; use synthetic oil
Engine oil	API Service Class SG, SH, or SJ synthetic oil	API	20°C to 4°C	1.9 L (2.0 qt.)	10W-30 for one range; 5W-20/5W-30 shown to -20C
Fuel		LP gas or natural gas			Minimum supply pressure 7--11 in. H2O (4--6 oz./in.2); multi-fuel system field convertible
Fuel	LP gas or natural gas				LP/natural gas minimum supply pressure 7--11 in. H2O (4--6 oz./in.2)
Fuel	LP vapor				Nominal fuel rating 2500 Btu/ft3 (93 MJ/m3); supply pressure 1.7--2.7 kPa (7-11 in. H2O); LP vapor conversion factors: 8.58 ft3 = 1 lb., 36.39 ft3 = 1 gal.
Fuel	LP vapor, 93 MJ/m3 (2500 Btu/ft3)				Nominal fuel rating
Fuel	LPG				Fuel supply pressure 1.7-2.7 kPa (7-11 in H2O); nominal fuel rating 2500 Btu/ft3 (93 MJ/m3); supply inlet 1/2 NPT
Fuel	Natural Gas				Fuel supply pressure 1.3-2.7 kPa (5-11 in H2O) for 8.5/12RES, 1.7-2.7 kPa (7-11 in H2O) for 18RES; nominal fuel rating 1000 Btu/ft3 (37 MJ/m3); supply inlet 1/2 NPT
Fuel	Natural Gas or LP Vapor				Generator set is CARB- and EPA-certified for both natural gas and LP vapor fuels. Multi-fuel system allows field conversion between natural gas and LP vapor.
Fuel	Natural gas				Nominal fuel rating 1000 Btu/ft3 (37 MJ/m3); supply inlet 1/2 NPT; supply pressure 1.7--2.7 kPa (7-11 in. H2O)
Fuel	Natural gas or propane (LP) vapor	Field-convertible multi-fuel; CARB emission certified			Clean-burning natural gas or propane (LP) vapor; air-cooled engine, no liquid coolant
Fuel	Natural gas, 37 MJ/m3 (1000 Btu/ft3)				Nominal fuel rating
Other	Bicarbonate of soda (baking soda) and water solution				Battery acid cleanup: 500 g (1 lb.) bicarbonate of soda to 4 L (1 gal.) water; also used to clean battery and cables
Other	Petroleum jelly, silicone grease, or other nonconductive grease				Coat battery terminals after reconnecting cables

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Fault codes

Code	Name	Meaning	Severity	Action
AF	Auxiliary fault input shutdown	Shutdown initiated by pushing the emergency stop switch (TRES models only). Not used on RES models.	Shutdown	Check the position of the emergency stop button. (TRES models only)
CC	Crank cycle
CO-3		Fault displayed if the CO parameter is set incorrectly	Shutdown
CO-6		Fault displayed if the CO parameter is set incorrectly	Shutdown
HB	High battery voltage warning	Fault code is displayed if the engine starting battery voltage rises above 16 VDC for more than 30 seconds when the engine is running. Not operative during the engine crank cycle; does not inhibit engine starting. Clears when the battery voltage returns to an acceptable level.	Warning	Check the battery rating and condition; check battery charger operation.
HE	High engine temperature shutdown	Shutdown occurs if the engine coolant temperature exceeds the maximum temperature for more than 5 seconds. This protective feature becomes active after the engine reaches the crank disconnect speed.	Shutdown	Check for blocked air inlets and exhaust outlets.
LB	Low battery voltage warning	Fault code is displayed if the engine starting battery voltage falls below 8 VDC for a 12 VDC system or below 16 VDC for a 24 VDC system for more than 10 seconds when the engine is not running. Does not inhibit engine starting; clears when voltage returns to limits for more than 10 seconds.	Warning	Check the battery rating and condition; check battery charger operation; charge or replace battery.
LCL	Low coolant level	Not used on air-cooled models.	Shutdown
LO P	Low oil pressure shutdown	Shutdown occurs if a low oil pressure condition exists for more than 5 seconds. Active 30 seconds after crank disconnect speed. Does not protect against low oil level.	Shutdown	Check for leaks in the lubrication system. Check the oil level and add oil if the level is low.
LOC	Loss of coolant	Not used on air-cooled models.	Shutdown
LOP	Low oil pressure shutdown	Shutdown occurs if low oil pressure exists for more than 5 seconds; active 30 seconds after crank disconnect speed. Does not protect against low oil level.	Shutdown	Check for leaks in the lubrication system. Check the oil level and add oil if the level is low.
OC	Overcrank shutdown	Shutdown occurs after 3 unsuccessful starting attempts. The crank cycle is set for three starting attempts of 15 seconds cranking and 15 seconds rest. The generator set also shuts down on OC if no engine rotation is sensed during cranking; shuts down 3 seconds after the fault is detected (locked rotor).	Shutdown	Check the fuel supply, spark plug, and battery. Check for loose connections. Contact an authorized distributor/dealer if the problem continues.
OF	Overfrequency shutdown	Shutdown when governed frequency exceeds 110% of system frequency setpoint for more than 5 seconds; active 10 seconds after engine start.	Shutdown	Contact an authorized distributor/dealer for service if the problem continues.
OS	Overspeed shutdown	Shutdown occurs if the engine speed exceeds 115% of the normal running speed for more than 1 second.	Shutdown	Contact an authorized distributor/dealer for service if the problem continues.
OU	Overvoltage shutdown	Shutdown occurs if voltage exceeds 120% of system nominal voltage for more than 2 seconds.	Shutdown	Contact an authorized distributor/dealer for service.
SCF0	Software Communication Fault 0	Indicates a software or communication problem within the controller.	Shutdown	Replace the controller. Contact an authorized distributor/dealer for service.
UF	Underfrequency shutdown	Shutdown when governed frequency falls below 90% of nominal system frequency for more than 5 seconds; active 10 seconds after engine start. (ADC-RES: below 54 Hz.)	Shutdown	Reduce the load and restart the generator set; contact distributor/dealer if problem continues
UU	Undervoltage shutdown	Shutdown occurs if voltage falls below 80% of the nominal system voltage for more than 10 seconds.	Shutdown	Reduce the load and restart the generator set; contact distributor/dealer if problem continues

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Procedures

ADC-RES Controller Configuration (Cn setting) adjustment

⚠ The controller automatically exits configuration mode without saving changes after about 1 minute if no buttons are pressed.

Enter the configuration mode while the engine is not running by following the Figure 26 sequence.
Step through the parameters to the communication setting Cn parameter.
Use the up and down arrow buttons to change the Cn setting to Cn01, if necessary.
Press to SAVE CHANGES (YES) before exiting the configuration mode.
Move the generator set master switch to OFF/RESET.

Controller Configuration adjustment

⚠ Be sure to save the new settings immediately before exiting the configuration mode; changes are lost if the controller times out (about 1 minute).

Hold the Select button and move the master switch to RUN to enter configuration mode.
Press the down arrow key then the up arrow key 3 times to enter configuration mode (password).
Set the voltage/frequency parameter Uu for the model.
Set the unit configuration parameter Uc (marine, standby, mobile).
Set the engine type parameter Ec.
Press the up arrow at the Adnc display to enter advanced configuration mode.
Set the engine data input type Ed.
Set the battery voltage Bt (12 or 24 VDC).
Set the communications parameter Cn.
Enter save mode and save your settings before exiting.

Frequency Adjustment Procedure adjustment

⚠ Hazardous voltage. Operate the generator set only when all guards and electrical enclosures are in place.

Tools: frequency meter

Open the generator set line circuit breaker.
Attach a frequency meter to the AC output leads.
Start and run the generator set until normal operating temperature (at least 10 minutes).
Use the ADC controller to adjust the electronic governor speed (parameter 4P) for 60 Hz (or 50 Hz).
Check stability with no load; decrease gain (parameter 5P) until stable if speed hunts or surges.
Repeat steps 4 and 5 to obtain rated frequency and stable operation.
Save the settings.
Apply rated load and observe frequency; no load and full load frequencies should be within 0.4 Hz of rated.
Check for hunting and surging at full load; increase gain until engine hunts, then decrease in small steps.
Remove the load and observe frequency; repeat step 4 if frequency changed.

Fuel Conversion Procedure (Models with Fuel Block) adjustment

⚠ Explosive fuel vapors. Use extreme care when handling, storing, and using fuels.

Disable genset: master switch OFF, disconnect battery charger, disconnect battery negative lead first.
Turn off fuel supply.
Remove hose clamp and fuel hose from hose fitting in the fuel metering valve.
Remove hose fitting from the natural gas outlet port.
Remove plug from LP port; clean, apply pipe sealant, install plug into natural gas port.
Clean hose fitting, apply pipe sealant, install fitting into LP port.
Slide hose onto fitting and secure with clamp.
For 12 kW models: connect DSAI leads together for natural gas (disconnect for LP).
Connect and turn on new fuel supply; reconnect battery negative last; reconnect battery charger.
Start genset and check for leaks using a gas leak detector.

Fuel Conversion Procedure (natural gas to LP vapor) adjustment

⚠ Do not adjust the factory-sealed fuel-metering adjustments on the fuel block.

⚠ Explosive fuel vapors can cause severe injury or death.

⚠ Accidental starting can cause severe injury or death.

Tools: Gas leak detector

Place the master switch in OFF, disconnect battery charger power, disconnect battery (negative lead first), and turn off fuel supply.
Remove the hose clamp and fuel hose from the hose fitting in the fuel block.
Remove the hose fitting from the natural gas outlet port in the fuel block.
Remove the plug from the LP port, clean it, apply fresh pipe sealant, and install it into the natural gas outlet port.
Clean the hose fitting, apply fresh pipe sealant to the threads, and install it into the LP port.
Slide the hose onto the fitting and secure it with the clamp.
For 12RES only: connect the DSAM leads together for natural gas (disconnect for LP vapor).
Connect and turn on the new fuel supply; recheck the master switch is OFF.
Reconnect the battery (negative lead last) and reconnect battery charger power.
Start the generator set by moving the master switch to RUN and check for leaks with a gas leak detector.
Move the generator set master switch to the AUTO position.

Fuel Metering Valve Adjustment Procedure adjustment

⚠ Adjusting fuel metering valves on emission-certified gensets may void the emission certification. Only trained authorized technicians may adjust.

Tools: Digital voltmeter (DVM), UEGO oxygen sensor service kit GM29385, Load bank

Disable genset (master switch OFF, disconnect battery charger).
Remove oxygen sensor plug from exhaust manifold and install oxygen sensor.
Connect oxygen sensor to engine starting battery, control module, and voltmeter.
Reconnect battery charger, start genset, and run to normal operating temperature.
Apply rated load; measure oxygen sensor output voltage (potential to ground).
Adjust fuel metering valve to obtain specified oxygen sensor output.
Seal metering valve adjustment screws with thread sealant.
Remove load and cool genset 5-10 minutes; stop genset.
Disconnect battery negative lead first; allow exhaust to cool.
Remove oxygen sensor and reinstall exhaust plug with antiseize; reconnect battery negative lead last and battery charger.

Mechanical Governor Arm Adjustment Procedure adjustment

⚠ Accidental starting can cause severe injury or death.

Tools: Nail

Make sure throttle linkage is connected to governor arm and carburetor throttle lever.
Loosen the hex nut holding the governor lever to the cross shaft.
Move governor lever toward carburetor as far as it will go (wide open throttle) and hold.
Insert a nail into the hole in the cross shaft and rotate the shaft counterclockwise as far as it will turn; tighten hex nut and remove nail.

Output Voltage and Frequency Adjustment adjustment

⚠ The generator set must be running during these adjustments.

⚠ The engine speed (frequency) adjustment menus are not accessible on models with mechanical governors.

Tools: multimeter

Move the master switch to RUN; the engine starts and runtime hours display.
Hold the Select button about 5 seconds until the program version number displays.
Press the down arrow key then the up arrow key 3 times to enter adjustment mode.
1P: adjust voltage coarse in large increments (approximately 5-7 volts per step).
2P: adjust voltage fine in smaller increments (approximately 0.5-0.7 volts per step).
Adjust voltage stability (gain) coarse and fine.
3P: set volts/Hz (00=low, 09=high).
4P: adjust engine governor speed coarse and fine.
5P: adjust engine governor stability (gain) coarse and fine.
Enter SAVE mode and save settings before exiting the adjustment mode.

RDC2 Voltage Calibration Using SiteTech adjustment

Tools: digital voltmeter, personal computer, SiteTech software

Connect PC to controller via USB
With generator off, connect multimeter across L1/L2 (AC volts)
Start generator set
Compare voltmeter reading to controller display
Calculate new Genset Calibration Factor Voltage using (Vmeter / Vcontrol) x Fold = Fnew
Enter new value into SiteTech and click Apply Changes
Verify voltmeter matches controller display
Repeat for L2-L3 and L3-L1 if three-phase
Press OFF to stop generator set

RDC2 Voltage Calibration Using the Controller Keypad adjustment

Tools: digital voltmeter

With generator off, connect digital multimeter across L1 and L2, set to AC volts
Start generator set with RUN button
Navigate to Generator Metering menu, press Select; Volts L1-L2 displayed
Press Select; voltage number flashes
Use up/down arrows to match voltmeter reading
Press Select to confirm
Step to Return screen
Press OFF to stop generator set

VSC Current (Load) Calibration Using the Controller Keypad adjustment

Tools: clamp-on DC current probe or DC current meter

Connect DC current probe/clamp meter to measure generator current
Start generator with RUN button
Adjust system voltage to obtain rated current output with battery bank attached (or use load bank)
Trip output breaker
Navigate to Generator Metering menu, select Generator Load
Press and hold Select for No-Load Calibration; verify breaker open, confirm Yes
Close output breaker; verify rated output current, confirm Yes
Verify displayed load is correct; recalibrate if necessary
Press OFF to stop generator set

Voltage Adjustment Procedure adjustment

⚠ Hazardous voltage. Operate the generator set only when all guards and electrical enclosures are in place.

Tools: digital voltmeter, frequency meter

Connect a digital voltmeter from one side of the circuit breaker to the L0 terminal inside the controller assembly.
Start the generator set.
Enter the adjustment mode and increase or decrease voltage (parameter 1P) to the desired voltage.
Adjust the voltage gain (parameter 2P) until light flicker minimizes; save settings.
Check and readjust the voltage if necessary.
Set voltmeter to frequency; adjust engine governor speed (parameter 4P) to the cut-in frequency.
Set voltmeter to voltage; adjust volts/Hz (parameter 3P) until voltage begins to drop.
Set voltmeter to frequency; adjust engine governor speed (parameter 4P) to the operating frequency (50 or 60 Hz).
Readjust voltage gain (parameter 2P) until light flicker minimizes.
Check voltage; readjust voltage (parameter 1P) if necessary.
Save the settings.
Stop the generator set.

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Voltage reconnection

Voltage	Phase	Connection	Leads	Notes
		ATS emergency source lugs EL1 and EL2	6 ga. Red and Black	Torque to 12 Nm (9 ft lbs)
		DSAI (Digital Spark Advance) leads	65 and N5	Connect for natural gas; disconnect for LP
		Engine start leads 3 and 4 to the ATS	14 ga. Red and White/Red	Terminals ES3 and ES4 on P2, torque connector screws to 0.8 Nm (7 in lb)
		Field-connection terminal block — L1 and L2	Leads from transfer switch emergency source lugs to L1 and L2	See decal near the terminal block for connections
		Ground	6 ga. Uninsulated
		Neutral	6 ga. White
		Remote start	Controller leads 3 and 4	Connect leads 3 and 4 from the ADC 2100 controller to the ATS engine start terminals or a remote start/stop switch.
	single phase	AC output leads to AC circuit breaker	L1/L2 (black)	Connect output leads going to the transfer switch to the AC circuit breaker load side; route through flexible conduit to circuit breaker box.
	single phase	Equipment ground	Green	Connect the green lead to the equipment ground terminal (labeled GRD).
	single phase	Neutral	L0 (white)	Connect the L0 white leads from the ATS and the main panel to the neutral terminal.
100 VAC	1	1Ph, 2W		Uu00; 60 Hz
100 VAC	1	1Ph, 3W		Uu00; 60 Hz
100/200	1	Single
100/200	3	Delta
100/200 VAC	1	1Ph, 3W		Uu08; 60 Hz
110	Single (L0-L1)	Factory two-pole circuit breaker		50 Hz; not reconnectable
110	Single (L0-L2)	Factory two-pole circuit breaker		50 Hz; not reconnectable
110 VAC	1	1Ph, 2W		Uu05; 50 Hz
110 VAC	1	1Ph, 3W		Uu05; 50 Hz
110 volt	1	L0-L1		50 Hz; 3-wire configuration; 8.5/12RES not reconnectable
110 volt	1	L0-L2		50 Hz; 3-wire configuration; 8.5/12RES not reconnectable
110/190 VAC	3	Wye		Uu17; 50 Hz
110/220	1	Single
110/220	3	Delta
110/220 VAC	1	1Ph, 3W		Uu07; 50 Hz
110/220 VAC	1	Dogleg		Uu07; 50 Hz
110/220 VAC	3	Delta		Uu15; 50 Hz
115 VAC	1	1Ph, 2W		Uu05; 50 Hz
115/200 VAC	3	Wye		Uu23; 50 Hz
115/230	1	Single

Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.

Common questions

What is the oil capacity of the Kohler CH740 4-Cycle?

The Kohler CH740 4-Cycle engine has an oil capacity of 1.9 liters.

What is the displacement of the Kohler CH740 4-Cycle?

The Kohler CH740 4-Cycle has a displacement of 0.725 liters with 2 cylinders.

Which generators use the Kohler CH740 4-Cycle engine?

The Kohler CH740 4-Cycle powers 2 generator set(s), including Kohler 12RES, Kohler 6VSG.

What is a common problem with the Kohler CH740 4-Cycle engine?

A commonly reported issue on generators using the Kohler CH740 4-Cycle is: Gas fuel leaks can cause an explosion.. Fix: Check the LP vapor gas or natural gas fuel system for leakage by using a soap and water solution with the fuel system test pressurized to 6–8 ounces per square inch (10–14 inches water column). Do not use a soap solution containing either ammonia or chlorine because both prevent bubble formation. A successful test depends on the ability of the solution to bubble..