Facts About Generators
GeneratorsDirectoryCompareRepairEnginesControllersPartsManufacturersGuides
Search models or part #
Home›Engines›Kohler KT725

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 Kohler, including the 10RESV and 12RESV. It holds 1.9 L (0.5 gal) of oil.

Also known as: Kohler KT725

0.725 L
Displacement
2
Cylinders
3600 rpm
Rated speed
1.9 L
Oil capacity
On this pageSpecsGenerator setsMaintenanceFAQService intervalsTorque & specsFluidsProceduresWiring

Engine specifications

Oil capacity1.9 L
Displacement0.725 L
Cylinders2
Aspirationair-cooled
Rated speed3600 rpm

Common problems

8
  • The generator set does not crank.
    Cause: Battery weak or dead.
    Fix: Recharge or replace the battery.
  • 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.
  • Gererator thermostat tripped.
    Cause: For trips other than temperature (nuisance trips),
    Fix: Reset the thermostat. See Section 2.6.
  • Generator set in the OFF mode.
    Fix: Press the RUN button to start the engine or press AUTO to allow remote starting.
  • Fault shutdown.
    Fix: Check the controller display for fault messages. See Section 2.5. Correct the fault condition and reset the controller.
  • Controller display is off.
    Cause: Low or no battery voltage.
    Fix: Check connections. Check generator set battery.
  • 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.
  • Explosion
    Cause: Fuel system leakage
    Fix: Check LPG vapor 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).

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

Maintenance schedule

ItemSpecCapacityPart #Interval
Oil filterCartridge type—100 hr
Oil1.9 L—100 hr

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

Service intervals

18
ItemActionHoursMonthsNotes
Oil levelCheck8 hrBefore each use and every 8 hours
engine oil levelCheck8 hrCheck before each use; for extended operation check every 8 hours
OilChange100 hr12 moYearly or 100 hours
Oil filterReplace100 hr12 moYearly or 100 hours
Valve lash (8RESV/L)Adjust100 hr100 hours
valve lash (8RESV)Check100 hr8RESV models only; requires authorized service
Air cleanerReplace150 hr12 moYearly or 150 hours
air cleanerOther150 hr12 moService more frequently under dusty conditions
engine oil and filterChange400 hr12 moUse 5W-30 synthetic oil
Crankcase breather hoseClean500 hr12 moYearly or 500 hours
Spark plugsReplace500 hr12 moYearly or 500 hours
Stepper motor coupling and bushingReplace500 hr500 hours
Valve lash (10/12RESV/L)Adjust500 hr500 hours
valve lash (10/12RESV)Check500 hr10/12RESV models only; requires authorized service
Battery cleaner operationCheck1 moMonthly
Battery electrolyte levelCheck12 moYearly
Fuel flexible linesInspect3 moQuarterly
batteryCheck1 moMonthly 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

8
TypeItemValueUnitCondition
Spark plug gapSpark plug gap0.508mmAll models
SpeedFrequency regulation steady state1.0%%
TemperatureCarburetor heater thermostat OFF16 ± 3C (60 ± 5F)
TemperatureCarburetor heater thermostat ON4 ± 4C (40 ± 7F)
TemperatureThermostat OFF16 ± 3°CThermostat OFF (60 ± 5°F)
TemperatureThermostat ON4 ± 4°CThermostat ON (40 ± 7°F)
TorqueSpark plug installation torque24.4 - 29.8NmInstallation
VoltageVoltage 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

FluidGradeStandardAmbientCapacityNotes
Engine oilFull Pressure system1.9 LWith filter
Engine oil5W-30API Service Class SG, SH, or SJ syntheticSynthetic oil oxidizes and thickens less; recommended for cleaner intake valves and pistons
Engine oil5W-30 API SG/SH/SJ syntheticAPI SG/SH/SJSynthetic oil recommended
FuelGasolineUnleaded gasolineLP 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

12
RDC2 Voltage Calibration Using SiteTech adjustment

Tools: digital voltmeter, personal computer, SiteTech software

  1. Connect PC to controller via USB
  2. With generator off, connect multimeter across L1/L2 (AC volts)
  3. Start generator set
  4. Compare voltmeter reading to controller display
  5. Calculate new Genset Calibration Factor Voltage using (Vmeter / Vcontrol) x Fold = Fnew
  6. Enter new value into SiteTech and click Apply Changes
  7. Verify voltmeter matches controller display
  8. Repeat for L2-L3 and L3-L1 if three-phase
  9. Press OFF to stop generator set
RDC2 Voltage Calibration Using the Controller Keypad adjustment

Tools: digital voltmeter

  1. With generator off, connect digital multimeter across L1 and L2, set to AC volts
  2. Start generator set with RUN button
  3. Navigate to Generator Metering menu, press Select; Volts L1-L2 displayed
  4. Press Select; voltage number flashes
  5. Use up/down arrows to match voltmeter reading
  6. Press Select to confirm
  7. Step to Return screen
  8. 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

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

  1. Open enclosure roof; locate controller and air cleaner.
  2. Turn off the generator set (master switch or controller OFF button, per model).
  3. Disconnect AC power to the generator set at the distribution panel breaker.
  4. Disconnect the starting battery, negative lead first.
  5. Check nameplate model/spec number and locate heater position per Figure 4.
  6. Remove the air cleaner cover if needed for access.
  7. Disconnect the heating element from the power cord at the plug connector.
  8. Insert the heating element into the threaded opening on the engine and tighten.
  9. Reconnect the power cord to the heater.
  10. Route and connect the power cord per the applicable model wiring option (steps 10-12).
  11. Replace the air cleaner cover if it was removed.
  12. Affix decal GM22387 onto the air cleaner cover.
  13. Reconnect the starting battery, negative lead last.
  14. Reconnect AC power by closing the distribution panel breaker.
  15. 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.

  1. Open the enclosure roof.
  2. Press the OFF button on the generator set controller.
  3. Disconnect AC power to the generator set at the distribution panel breaker.
  4. Disconnect the starting battery, negative lead first.
  5. Locate the carburetor heater per Figure 14; remove side panel or air cleaner cover if needed.
  6. Remove and discard the M8 bolt from the carburetor at the heater location.
  7. Thread adapter GM91361 into the M8 hole.
  8. Insert carburetor heater GM57968 into the adapter and tighten.
  9. Connect the extension cord (GM91360 or 3-way GM95628) to the heater cord.
  10. Route the cord to the AC receptacle, securing away from throttle linkage and exhaust.
  11. Plug the cord into the AC receptacle on the generator bulkhead.
  12. Affix decal GM22387 onto the air cleaner cover.
  13. Reconnect the starting battery, negative lead last.
  14. Reconnect AC power by closing the distribution panel breaker.
  15. Press AUTO for standby operation and reinstall enclosure panels.
Installation Procedure, 17/18/20 kW Models installation

⚠ Disconnect battery cables before working on generator set; remove negative lead first.

⚠ Disconnect all power sources before opening enclosure.

⚠ Install heater before connecting power; allow to cool before servicing.

  1. Open enclosure roof; locate controller and engine air cleaner.
  2. Turn off generator set: 17/18RES/RESL move master switch OFF; 20RES/RESL press OFF and remove fuse F3; 20RESA/AL/B/C/CL/D press OFF.
  3. Disconnect AC power by opening circuit breaker in distribution panel.
  4. Disconnect engine starting battery, negative lead first.
  5. Check nameplate model/spec; see Figure 4 for heater location. Heater fits threaded opening on carburetor below air cleaner.
  6. Remove air cleaner cover if easier access needed.
  7. Disconnect heater element from power cord at plug connector (GM57968 or GM88228).
  8. Insert heating element into threaded opening on engine and tighten.
  9. Reconnect power cord to heater.
  10. For 17/18RES/RESL and 20RES/RESL: remove air intake panel; install bushing X-634-15 or X-634-16; route cord through bulkhead; plug into 120 VAC receptacle under controller.
  11. For 120 V 20RESA/AL/B/C/CL/D: route cord away from hot parts; plug into receptacle in engine compartment; use 3-way cord GM95628 if multiple accessories; secure excess cable.
  12. For 240 V 14/20RESA and 20RESC: remove controller screws, remove bulkhead knockout, route cord and insert plug; disconnect 120 VAC harness at 3-pin; connect 3-pin to new 240 VAC connector.
  13. Replace air cleaner cover if removed; affix decal GM22387 as shown.
  14. Check master switch OFF (17/18); reconnect battery, negative last; close distribution breaker. 20RES/RESL: reinstall fuse F3.
  15. For standby, move master switch to AUTO or press AUTO. Reinstall enclosure panels; close and lock roof.
Installation Procedure, Models 8-12RESV/RESVL installation

⚠ Disconnect battery cables before working on generator set; remove negative lead first.

⚠ Disconnect all power sources before opening enclosure.

⚠ Install heater before connecting power; allow to cool before servicing.

  1. Open enclosure roof.
  2. Press OFF button on generator set controller.
  3. Disconnect AC power by opening circuit breaker in distribution panel.
  4. Disconnect engine starting battery, negative lead first.
  5. See Figure 13 for heater location. Remove louvered side panel and/or air cleaner cover for access if necessary.
  6. Remove and discard M8 bolt from carburetor at heater location.
  7. Thread adapter GM91361 into M8 hole.
  8. Insert carburetor heater GM57968 into adapter and tighten.
  9. Connect extension cord GM91360 or 3-way extension cord GM95628 to heater cord.
  10. Route cord to AC receptacle as shown; secure with cable ties away from throttle linkage and exhaust.
  11. Plug cord into AC receptacle on generator bulkhead.
  12. Affix decal GM22387 onto air cleaner cover.
  13. Reconnect battery, negative lead last.
  14. Reconnect AC power by closing circuit breaker.
  15. For standby, press AUTO. Reinstall enclosure panels; close and lock roof.
Air Cleaner Service (8RESV/RESVL) maintenance

⚠ Do not wash paper element or clean with pressurized air

  1. Press OFF button and disconnect utility power and battery
  2. Loosen cover retaining knobs and remove cover
  3. Remove paper element
  4. Replace element if dirty, bent, or damaged
  5. Check air cleaner base for condition
  6. Check element cover for damage
  7. Reinstall paper element and air cleaner cover
  8. Secure cover with retaining knobs
  9. Reconnect battery and utility power
Firmware Update Using SiteTech maintenance

⚠ Do not load RDC2.4 firmware onto a red- or green-board controller

Tools: personal computer, USB cable, SiteTech software

  1. Download latest firmware file (.bin) from Kohler Power Resource Center or dealer portal
  2. Connect controller to PC via USB cable
  3. Start SiteTech; program recognizes connected device
  4. Click Update Firmware
  5. Browse to and select firmware file, click Open
  6. Verify current/new version and file name, click Update Firmware
  7. Wait for 'Firmware Updated Successfully' message, click Close
Oil Change Procedure maintenance

⚠ Accidental starting can cause severe injury or death.

⚠ Risk of fire from fuel system.

⚠ Do not smoke near carburetor or fuel system.

Tools: oil filter wrench, funnel, rags, drain pan

  1. Press OFF button to shutdown generator set.
  2. Disconnect utility power to generator set.
  3. Disconnect engine starting battery (negative lead first).
  4. Remove side panel on exhaust side of enclosure.
  5. Clean area around dipstick and oil fill cap.
  6. Cover alternator with rags to prevent oil spillage.
  7. Insert drain tube onto oil drain valve.
  8. Open oil drain valve and allow oil to drain completely.
  9. Close oil drain valve and remove drain tube.
  10. Clean area around oil filter.
  11. Loosen oil filter with wrench and remove carefully.
  12. Clean gasket sealing surface.
  13. Apply light coat of clean oil to new filter seal.
  14. Thread new oil filter by hand until resistance, then 3/4 turn more.
  15. Fill engine with recommended oil to Full mark on dipstick.
Exercise the Generator Set operation

⚠ Do not run loaded without proper load

  1. Access exercise menu on controller
  2. Select unloaded cycle exercise with complete diagnostics
  3. Exercise runs at no load for system diagnostics
  4. Monitor for fault messages
Generator Set Operation - Local Starting operation

⚠ Hazardous voltage present

  1. Refer to prestart checklist (Section 2.1)
  2. Use local start controls to start generator
  3. Monitor controller display for voltage and frequency
  4. Engine will reach full speed and stabilize output

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

VoltagePhaseConnectionLeadsNotes
100/2001Single
100/2003Delta
110/2201Single
110/2203Delta
115/2301Single
1201SingleGenset System Voltage/Frequency/Phase table for controller setup
120/2083Wye
120/2401Single
120/2403Delta
127/2203Wye
2201Single
220/3803Wye
2301Single
230/4003Wye
2401Single
240/4163Wye
277/4803Wye

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

11
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 24-393-04-S KuduParts $12.00 015-0051-00 FridayParts $175.00 24-755-141-S KuduParts $16.00 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 2 generator set(s), including 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 does not crank.. Cause: Battery weak or dead.. Fix: Recharge or replace the battery..