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Kohler KT725 Engine

The Kohler KT725 is a 0.72 L 2-cylinder air-cooled engine rated at 3600 rpm. It powers generator sets from Generac and Kohler, including the 10RESV, 12RESV, 10RESV and 12RESV. It holds 1.9 L (0.5 gal) of oil.

Also known as: Kohler KT725

0.725 L

Displacement

Cylinders

3600 rpm

Rated speed

1.9 L

Oil capacity

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

Engine specifications

Oil capacity	1.9 L
Displacement	0.725 L
Cylinders	2
Aspiration	air-cooled
Rated speed	3600 rpm

Generator sets powered by this engine

Shared across brands: Generac, Kohler

Generac 10RESVGenerac 12RESVKohler 10RESV Kohler 12RESV

How to read your Kohler engine serial & model number →

Common problems

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
Generator set stops suddenly
Cause: Low oil pressure shutdown
Fix: Check for oil leaks. Check the oil level and add oil if necessary
The generator set does not crank
Cause: Battery weak or dead
Fix: Recharge or replace the battery
No AC output
Cause: Line circuit breaker in the OFF position
Fix: Place the circuit breaker in the ON position
Controller display is off
Cause: Low or no battery voltage
Fix: Check connections; Check generator set battery
MainPwrOverL Shutdown — controller internal circuit protection activated MainPwrOverL Shutdown
Fix: Press OFF to reset. Contact an authorized Kohler distributor/dealer for service
Low output or excessive drop in voltage
Cause: Generator set overloaded
Fix: Reduce the load
Controller display backlight is off
Cause: Backlight turns off after about 1 minute with no activity
Fix: Backlight will turn on when a button is pressed or the generator set starts
Accy PwrOver Warning — controller internal circuit protection activated Accy PwrOver Warning
Fix: Press OFF to reset. Contact an authorized Kohler distributor/dealer for service

Compiled from service & troubleshooting documentation across every generator set that uses the Kohler KT725.

Maintenance schedule

Item	Spec	Capacity	Part #	Interval
Oil filter	Cartridge type		—	100 hr
Oil		1.9 L	—	100 hr

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

Repair guides

Step-by-step procedures compiled from the Kohler service manual for this engine.

Service intervals

Item	Action	Hours	Months	Notes
Oil level	Check	8 hr		Before each use and every 8 hours
engine oil level	Check	8 hr		Check before each use; for extended operation check every 8 hours
Oil	Change	100 hr	12 mo	Yearly or 100 hours
Oil filter	Replace	100 hr	12 mo	Yearly or 100 hours
Valve lash (8RESV/L)	Adjust	100 hr		100 hours
valve lash (8RESV)	Check	100 hr		8RESV models only; requires authorized service
Air cleaner	Replace	150 hr	12 mo	Yearly or 150 hours
air cleaner	Other	150 hr	12 mo	Service more frequently under dusty conditions
engine oil and filter	Change	400 hr	12 mo	Use 5W-30 synthetic oil
Crankcase breather hose	Clean	500 hr	12 mo	Yearly or 500 hours
Spark plugs	Replace	500 hr	12 mo	Yearly or 500 hours
Stepper motor coupling and bushing	Replace	500 hr		500 hours
Valve lash (10/12RESV/L)	Adjust	500 hr		500 hours
valve lash (10/12RESV)	Check	500 hr		10/12RESV models only; requires authorized service
Battery cleaner operation	Check		1 mo	Monthly
Battery electrolyte level	Check		12 mo	Yearly
Fuel flexible lines	Inspect		3 mo	Quarterly
battery	Check		1 mo	Monthly for first year; annually thereafter

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
Spark plug gap	Spark plug gap	0.508	mm	All models
Speed	Frequency regulation steady state	1.0%	%
Temperature	Carburetor heater thermostat OFF	16 ± 3	C (60 ± 5F)
Temperature	Carburetor heater thermostat ON	4 ± 4	C (40 ± 7F)
Temperature	Thermostat OFF	16 ± 3	°C	Thermostat OFF (60 ± 5°F)
Temperature	Thermostat ON	4 ± 4	°C	Thermostat ON (40 ± 7°F)
Torque	Spark plug installation torque	24.4 - 29.8	Nm	Installation
Voltage	Voltage regulation (no-load to full-load)	±1.0%	RMS

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	Capacity	Notes
Engine oil		Full Pressure system	1.9 L	With filter
Engine oil	5W-30	API Service Class SG, SH, or SJ synthetic		Synthetic oil oxidizes and thickens less; recommended for cleaner intake valves and pistons
Engine oil	5W-30 API SG/SH/SJ synthetic	API SG/SH/SJ		Synthetic oil recommended
Fuel	Gasoline	Unleaded gasoline		LP or natural gas capable

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

Procedures

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

Obtain DC2 Controller Password and Serial Number diagnostic

Press OFF and verify that the generator set is not running.
Press and hold the Exercise button until Press Again to Reset OnCue Plus PW is displayed.
Release the Exercise button and press it again within 5 seconds.
Write down the serial number (S/N) and password.

Obtain RDC/DC Controller Password diagnostic

Press OFF to place the controller into OFF mode.
Press the down arrow button (RDC) or exercise button (DC) 5 times.
Note the four-digit code displayed on the controller; this is the controller password.
Write down the password and press OFF to clear the display.

Obtain RDC2 or VSC Controller Password and Serial Number diagnostic

Press the controller down arrow button to navigate to the Networking Information menu.
Follow the reset password procedure shown in Figure 1-3.
Write down the serial number (S/N) and password displayed for 10 seconds.

Power Cycle the Controller diagnostic

Disconnect all input power for two minutes to allow capacitors to discharge.
Remove the battery negative cable or disconnect P1 from the back of the controller.
Disconnect the battery charger 120 VAC input power supply or disconnect P5 from the back of the controller.
Unplug the USB mini-B connector from the front of the controller if plugged in.
Wait two minutes, then reconnect power, hooking up battery power (P1) first.

Use Telnet to Check Server Connection diagnostic

Tools: Command prompt, Telnet Client

Activate Telnet Client on the computer if necessary.
Open a command prompt window.
Enter telnet devices.kohler.com 5253.
Successful connection displays the symbols shown in Figure 3-8.

Connect OnCue Plus for RDC/DC installation

Install the Ethernet option board on the generator set controller. See TT-1566.
Connect a network cable from the Ethernet board to your router or modem.

Connect OnCue Plus for RDC2/DC2/VSC installation

Set the controller password before connecting the generator set Ethernet cable to the router.
Connect the RJ45 inline connector included in the OnCue Plus kit to the Ethernet cable inside the generator enclosure.
Connect one end of the customer-provided network cable to the RJ45 connector.
Connect the other end of the network cable to the customer router or modem.

Install Carburetor Heater, 17/18/20 kW Models installation

⚠ Accidental starting can cause severe injury or death; disconnect battery cables before working on the generator set, negative lead first.

⚠ Hazardous voltage will cause severe injury or death; disconnect all power sources before opening the enclosure.

⚠ Hot surfaces: disconnect power to the heater and allow it to cool before servicing.

Open enclosure roof; locate controller and air cleaner.
Turn off the generator set (master switch or controller OFF button, per model).
Disconnect AC power to the generator set at the distribution panel breaker.
Disconnect the starting battery, negative lead first.
Check nameplate model/spec number and locate heater position per Figure 4.
Remove the air cleaner cover if needed for access.
Disconnect the heating element from the power cord at the plug connector.
Insert the heating element into the threaded opening on the engine and tighten.
Reconnect the power cord to the heater.
Route and connect the power cord per the applicable model wiring option (steps 10-12).
Replace the air cleaner cover if it was removed.
Affix decal GM22387 onto the air cleaner cover.
Reconnect the starting battery, negative lead last.
Reconnect AC power by closing the distribution panel breaker.
For standby operation, move switch to AUTO and reinstall enclosure panels.

Install Carburetor Heater, Models 8-12RESV/RESVL installation

⚠ Accidental starting can cause severe injury or death; disconnect battery cables before working on the generator set, negative lead first.

⚠ Hazardous voltage will cause severe injury or death; disconnect all power sources before opening the enclosure.

⚠ Hot surfaces: install the heater before connecting it to power; disconnect power and allow it to cool before servicing.

Open the enclosure roof.
Press the OFF button on the generator set controller.
Disconnect AC power to the generator set at the distribution panel breaker.
Disconnect the starting battery, negative lead first.
Locate the carburetor heater per Figure 14; remove side panel or air cleaner cover if needed.
Remove and discard the M8 bolt from the carburetor at the heater location.
Thread adapter GM91361 into the M8 hole.
Insert carburetor heater GM57968 into the adapter and tighten.
Connect the extension cord (GM91360 or 3-way GM95628) to the heater cord.
Route the cord to the AC receptacle, securing away from throttle linkage and exhaust.
Plug the cord into the AC receptacle on the generator bulkhead.
Affix decal GM22387 onto the air cleaner cover.
Reconnect the starting battery, negative lead last.
Reconnect AC power by closing the distribution panel breaker.
Press AUTO for standby operation and reinstall enclosure panels.

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	Notes
100/200	1	Single
100/200	3	Delta
110/220	1	Single
110/220	3	Delta
115/230	1	Single
120	1	Single	Genset System Voltage/Frequency/Phase table for controller setup
120/208	3	Wye
120/240	1	Single
120/240	3	Delta
127/220	3	Wye
220	1	Single
220/380	3	Wye
230	1	Single
230/400	3	Wye
240	1	Single
240/416	3	Wye
277/480	3	Wye

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

Aftermarket parts that fit this engine

32-584-06-S FridayParts $16.00 E7172-00430 FridayParts $22.98 24-393-02 FridayParts $29.99 24-393-04 FridayParts $29.99 24-393-16 FridayParts $29.99 24-393-16-S KuduParts $12.00 FridayParts $13.99 24-393-04-S KuduParts $12.00 FridayParts $13.99 015-0051-00 FridayParts $175.00 24-755-141-S KuduParts $16.00 FridayParts $18.90 ZT730 FridayParts $10.49 FP-XP-0042853

Parts listed by aftermarket suppliers as fitting this engine — leads compiled from supplier catalogs; verify the exact part for your serial number.

Common questions

What is the oil capacity of the Kohler KT725?

The Kohler KT725 engine has an oil capacity of 1.9 liters.

What is the displacement of the Kohler KT725?

The Kohler KT725 has a displacement of 0.725 liters with 2 cylinders.

Which generators use the Kohler KT725 engine?

The Kohler KT725 powers 4 generator set(s), including Generac 10RESV, Generac 12RESV, Kohler 10RESV, Kohler 12RESV.

How often should you change the oil in the Kohler KT725?

The Kohler KT725 oil change interval is every 100 hours.

What is a common problem with the Kohler KT725 engine?

A commonly reported issue on generators using the Kohler KT725 is: 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.