Home›Engines›Generac OHV

Generac OHV Engine

Name: Generac OHV Engine
Brand: Generac

The Generac OHV is a 4.2 L 1-cylinder air-cooled engine rated at 3600 rpm. It powers generator sets from Generac, including the CorePower 7 kW, G006998-1, GP1800 and GP3000i. It holds 1 L (0.3 gal) of oil.

Also known as: Generac OHV

4.2 L

Displacement

Cylinders

3600 rpm

Rated speed

1.0 L

Oil capacity

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

Engine specifications

Oil capacity	1.0 L
Displacement	4.2 L
Cylinders	1
Aspiration	Air-Cooled
Rated speed	3600 rpm

Generator sets powered by this engine

Generac CorePower 7 kW Generac G006998-1 Generac GP1800 Generac GP3000i Generac GP3250 Generac GP3300 Generac GP3500iO Generac GP5000 Generac GP5500Generac GP6000EGenerac GP6500E Generac GP7500 Generac GP7500E DF Generac IQ3500 Generac LP3250 Generac PowerPact 006998-0 Generac Powerpact

How to read your Generac engine serial & model number →

Common problems

No AC output.
Cause: 1. Generator is overloaded. 2. Inverter module is overheated. 3. Short circuit in electrical device. 4. Defective inverter assembly.
Fix: 1. Disconnect all loads. Shut down generator to reset module. Reduce loads, restart generator. 2. Verify service door is ON. Let cool 15 minutes by running engine without AC output. Press and hold Reset button on control panel, restart generator. 3. Verify condition of extension cords and items being powered. Press and hold Reset button on control panel. 4. Contact IASD.
Engine won't start.
Cause: 1. Dial turned off. 2. Out of fuel. 3. Defective spark plug. 4. Plugged fuel filter. 5. Defective or stuck Dial assembly. 6. Incorrect engine oil level. 7. Defective ignition coil. 8. Carb is flooded. 9. Throttle plate closed.
Fix: 1. Turn on Dial. 2. Fill fuel tank. 3. Replace spark plug. 4. Replace fuel and fuel filter. 5. Contact IASD. 6. Check/fill engine oil. 7. Contact IASD. 8. Drain carb. 9. Open throttle plate (push toward back of unit).
Engine will not start; or starts and runs rough.*
Cause: 1. Choke is stuck or left on. 2. Dirty or clogged air filter. 3. Defective or dirty spark plug. 4. Dirty fuel filter. 5. Dirty or gummed up carburetor. 6. Unit not warmed up. 7. Spark arrestor clogged.
Fix: 1. Turn choke off. 2. Clean or replace air filter. 3. Replace spark plug. 4. Replace fuel and fuel filter. 5. Clean carburetor. 6. Gradually adjust Dial and reduce choke until engine runs smoothly in RUN position. 7. Clean spark arrestor.
Engine starts, then shuts down.
Cause: 1. Out of fuel. 2. Incorrect engine oil level. 3. Contaminated fuel. 4. Defective low oil level switch.
Fix: 1. Fill fuel tank. 2. Check engine oil level. 3. Contact IASD. 4. Contact IASD.
Fuel leaks from drain hoses.
Cause: 1. Carburetor drain in bowl is not closed.
Fix: 1. Turn valve clockwise to close.
Recoil Cord Will Not Pull
Cause: BAD
Fix: TEST 49 – TEST RECOIL FUNCTION TEST 50 – TEST ENGINE FUNCTION REPAIR OR REPLACE
Engine ‘Hunts’ / Erratic Idle
Cause: NO SURGING STILL SURGING
Fix: TEST 29 – CHECK CARBURETION GOOD TEST 40 – CHECK AND ADJUST GOVERNOR
Engine Will Not Crank
Cause: NO VOLTAGE MEASURED 12 VDC MEASURED
Fix: RECHARGE OR REPLACE BATTERY – CLEAN, REPAIR OR REPLACE BAD CABLE(S) BAD REPLACE BAD GOOD NO VOLTAGE MEASURED BAD 12 VDC MEASURED REPLACE STARTER MOTOR IF DEFECTIVE GOOD CHECK FOR MECHANICAL BINDING OF THE ENGINE OR ROTOR
Engine Turns Over But Will Not Start
Cause: NO SPARK
Fix: TEST 39 – REMOVE WIRE 18 / SHUTDOWN LEAD NO SPARK GOOD BAD REPLACE SWITCH BAD CHECK ENGINE OIL LEVEL TEST 45 – CHECK OIL LEVEL SWITCH TEST 24 – TEST OFF-ON SWITCH REPLACE SWITCH REPLENISH OIL REPLACE LOW OIL ALARM GOOD OIL LEVEL O.K. OIL LEVEL LOW BAD
Engine Starts Hard and Runs Rough
Cause: ADJUST VALVES AND RETEST
Fix: BAD TEST 40 – CHECK AND ADJUST GOVERNOR TEST 38 – CHECK FLYWHEEL
Engine fires, but does not continue to run
Fix: Rotate the Off/On/Choke dial to OFF and repeat starting instructions
Unit Shuts Down for Low Oil
Fix: Problem 8
Overload output
Fix: Disconnect electrical loads prior to starting or stopping unit. Failure to do so could result in equipment and property damage.
Overload Light Is On
Fix: DISCONNECT LOAD, RESTART ENGINE AND CHECK AC OUTPUT AGAIN. (iX Units) DISCONNECT LOAD, PRESS AND HOLD RESET BUTTON, THEN RELEASE. IF OVERLOAD LIGHT GOES OUT, LOAD IS TO MUCH FOR THE UNIT. (iQ2000)
Output Fault 14

Compiled from service & troubleshooting documentation across every generator set that uses the Generac OHV.

Service intervals

Item	Action	Hours	Months	Notes
Engine oil level	Check	8 hr		at each use / every 8 hours
Engine oil level	Inspect	8 hr		Prior to each use or every 8 hours of operation
Oil level	Check	24 hr		Monthly or 24 hours of continuous operation
Oil and filter	Change	25 hr		First service — After first 25 hours of operation
Spark arrestor screen	Clean	50 hr		every 50 hours of operation or every season, whichever comes first
Air filter	Clean	100 hr	6 mo	clean/replace; replace parts if cannot be adequately cleaned
Engine oil	Change	100 hr	12 mo	First service — every 100 hours of run time thereafter
Muffler Screen	Clean	100 hr	6 mo	Every 100 Hours or Every 6 Months
Spark arrestor	Clean	300 hr	12 mo	Muffler Screen; Clean/Replace Spark Arrestor; inspect and clean screen every 100 hours or six months
Spark arrestor	Inspect	100 hr	12 mo	Every 100 hours or every year
Spark arrestor / muffler screen	Clean	100 hr	6 mo	Every 100 Hours or Every 6 Months
Air cleaner filter	Clean	200 hr	12 mo	Inspect/clean; clean more often in dirty/dusty conditions; replace if cannot be adequately cleaned
Complete tune-up	Other	200 hr	24 mo	To be completed by a Dealer
Oil	Change	200 hr	24 mo	2Y or 200 hours, whichever occurs first
Oil filter	Change	200 hr	24 mo	2Y or 200 hours
Scheduled maintenance	Change	200 hr	24 mo	Oil, oil filter, spark plugs recommended for maintenance kits
Crankcase breather hose	Check	300 hr	12 mo	Every 300 Hours or Every Season
Cylinder head	Check	300 hr		to be performed by IASD
Fittings/fasteners	Check	300 hr	12 mo	to be performed by IASD
Fuel filter	Replace	300 hr	12 mo	to be performed by IASD
Spark plug	Replace	300 hr	12 mo	every 300 hours or every season
Valve clearance	Adjust	500 hr	12 mo	First service — check/adjust after first 50 hours, then every 300 hours
Valve clearance	Check	300 hr	12 mo	First service — Check/adjust after first 50 hours, then every 300 hours thereafter or every year
Air cleaner	Clean	400 hr
Spark plug(s)	Clean	400 hr		Replace every 4 years or 400 hours
Battery (remove corrosion, ensure dryness)	Inspect		12 mo	Yearly
Battery charge state	Check		12 mo	Yearly
Battery electrolyte level	Check		6 mo	Unsealed batteries only; every 6 months
Battery terminals (clean and tighten)	Clean		12 mo	Yearly
Fuel lines and connections	Inspect		1 mo	Monthly; notify dealer if repair is needed
General condition (vibration, noise, leakage)	Inspect		1 mo	Notify dealer if repair is needed

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	Exhaust valve clearance	0.10 ± 0.02	mm (0.004" ± 0.001")	cold
Clearance	Flywheel magnet attraction distance (screwdriver test)	3/4 (19mm)	inch
Clearance	Intake valve clearance	0.10 ± 0.02	mm (0.004" ± 0.001")	cold
Gap	Spark plug gap	0.024-0.028	in (0.6-0.7 mm)
Gap	Spark plug gap	0.024-0.028 (0.6-0.7)	in/mm
Gap	Spark plug gap	0.028-0.031	inch (0.70-0.80 mm)
Gap	Spark plug gap	0.028-0.031 inch or (0.70-0.80 mm)	inch / mm
Gap	Spark plug gap	0.03	in
Gap	Spark plug gap	0.6-0.7	mm
Gap	Spark plug gap	0.76	mm (0.030 inch)
Gap	Spark plug gap	1.02	mm (0.040 inch)
Gap	Spark plug gap (GP1800/GP3250/GP5000/GP5500/GP6500)	0.028"-0.031" (0.7-0.8mm)	inch
Gap	Spark plug gap (GP7000/GP8000)	0.030" (0.76mm)	inch
Gap	Trigger pickup gap	0.20-0.30	mm
Other	1.5 Amp fuse rating	1.5	Amp
Other	AC output load test - frequency should not drop below	59	Hertz	load applied
Other	Capacitor rating - Alternator Configuration A	47	µf (440 VAC)
Other	Capacitor rating - Alternator Configuration B	28	µf
Other	Capacitor test tolerance	± 5	µf
Other	Cylinder leak down - normally acceptable leakage	20	percent
Other	LP vapor 1st stage regulator inlet pressure	approximately 30 psi at 0 °F, and 218 psi at 100 °F	psi	at stated temperatures
Other	Nominal amp draw of starter in generator	60	amps
Other	Spark plug installation tightening	3/8 to 1/2 turn beyond finger tight	turn
Other	Starter motor maximum amps	50	Amps	performance test
Pressure	Cylinder leak down - minimum air source	90	psi
Pressure	Cylinder leak down - regulated test pressure	80	psi
Pressure	Engine oil pressure - shut down threshold	below about 10	psi	engine running
Pressure	Fuel pressure to regulator - LP	10-12	inches water column (19-22 mm mercury)
Pressure	Fuel pressure to regulator - natural gas	3.5-7	inches water column (7-13 mm mercury)
Pressure	Minimum allowable compression pressure	60	psi	cold engine
Pressure	Normal engine oil pressure	35-40	psi	engine running
Pressure	Oil pressure switch rating	10	psi	single cylinder engines
Resistance	Brushless DPE winding resistance (Wire 2 to Wire 6)	0.97 and 1.13	Ohms
Resistance	Brushless stator winding resistance (11-22, 33-44)	0.12-0.14	Ohms
Resistance	Control Winding: Yellow-Yellow	0.16-0.18	Ohms
Resistance	DC Winding Blue	0.19-0.21	Ohms
Resistance	DC Winding Blue	0.86 ±15%	Ohms
Resistance	DC Winding: Green-Green	0.13-0.15	Ohms
Resistance	Exciter Windings - GP1800 (alt 0H8255/0J0819)	2.53	Ohms
Resistance	Exciter Windings - GP3250 (alt 0H2626/0H3578)	1.72	Ohms
Resistance	Exciter Windings - GP5500/GP/LP5500 (alt 0G9769/0J8363)	2.81	Ohms
Resistance	Exciter Windings - GP6500E (alt 0H9920/0K1291)	2.9 ± 10%	Ohms
Resistance	Exciter Windings - GP7500E DF-CO (alt A0001920613/A0000121536)	1.928	Ohms
Resistance	Exciter Windings - GP8000E COSTCO (alt 0J8438/0K9791)	1.626	Ohms
Resistance	Exciter Windings - LP3250 (alt 0J2561/0J6032)	2	Ohms
Resistance	Ignition Coil Winding (J1 Pin 5)	0.5	Ohms
Resistance	Ignition Coil Winding (J1 Pin 5)	0.7	Ohms
Resistance	Ignition Coil Winding (J1 Pin 5)	0.8	Ohms
Resistance	Ignition coil Pin 1 to Ground	1.7 ± 0.5	Ohms
Resistance	Ignition coil Spark Plug to Ground	12.5K ± 2K	Ohms
Resistance	Ignition: Blue-Yellow/Green	0.63-0.71	Ohms
Resistance	Main Coil of Stator	1.6 ± 0.4	Ohms
Resistance	Main Coil of Stator	1.9	Ohms
Resistance	Main Winding Brown	0.75-0.85	Ohms
Resistance	Main Winding Brown	0.97 ±15%	Ohms
Resistance	Main Winding Red 1-2	1.97-2.18	Ohms
Resistance	Main Winding Red 1-3	1.97-2.18	Ohms
Resistance	Main Winding Red 2-3	1.97-2.18	Ohms
Resistance	Power Windings - GP1800 (alt 0H8255/0J0819)	0.798	Ohms
Resistance	Power Windings - GP3250 (alt 0H2626/0H3578)	0.62	Ohms

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		Manufacturer recommendations		Oil must be purchased separately based on manufacturer recommendations
Engine oil	10W-30			Oil will need to be purchased separately based upon the recommendations listed.
Engine oil	10W-30 / SAE 30		0.6 L
Engine oil	10W-30 / SAE30			Recommended Oil
Engine oil	5W30		0.6 liter	GP1800/GP3250 oil capacity 0.634 quart (0.6 liter)
Engine oil	SAE 30			Oil will need to be purchased separately based upon the recommendations listed.
Engine oil	SAE 30 / 10W-30 / Synthetic 5W-30		0.6 L (0.6 qt.)
Engine oil	SAE 30 / 10W-30 / Synthetic 5W-30 (by climate)		0.6 L (0.6 qt.)
Engine oil	SAE 30, 10W-30, Synthetic 5W-30		0.6 L	Multi-viscosity options per ambient temperature
Engine oil	SAE 30, 10W-30, or Synthetic 5W-30		0.6 L	Use petroleum based oil (supplied) for engine break-in before using synthetic oil
Engine oil	Synthetic 5W-30			Oil will need to be purchased separately based upon the recommendations listed.
Engine oil	synthetic 5W-30			Below 10°F
Fuel		Unleaded	4.3 L	1.14 U.S. gallons fuel capacity
Fuel	Clean, fresh, unleaded gasoline, minimum 87 octane/87 AKI (91 RON), up to 10% ethanol		29.9 L (7.9 gal)	DO NOT use E85 or gas/oil mix
Fuel	Clean, fresh, unleaded gasoline; minimum 87 octane/87 AKI (91 RON); up to 10% ethanol acceptable		10.0 L	DO NOT use E85. DO NOT use a gas oil mix
Fuel	Clean, fresh, unleaded gasoline; minimum 87 octane/87 AKI (91 RON); up to 10% ethanol acceptable; DO NOT use E85		30.0 L	DO NOT use a gas oil mix; stabilize fuel prior to storage; tank capacity 30.0 L (7.9 gal)
Fuel	Liquid propane (LP) gas (vapor)	at least 2,500 Btus per cubic foot (93.15 megajoules per cubic meter)	250.0 gallons (946 liters)	Minimum LP tank size recommended when converting from natural gas
Fuel	Natural gas (pipeline)	at least 1,000 Btus per cubic foot (37.26 megajoules per cubic meter)		Unit is factory set to run on natural gas
Fuel	Unleaded		10.0 L (2.64 U.S. gallons)
Fuel	Unleaded gasoline		9.0 L (2.37 U.S. gallons)
Fuel	Unleaded gasoline, minimum 87 octane/87 AKI (91 RON), up to 10% ethanol acceptable; do not use E85		4.3 L	Do not use a gas oil mix; stabilize fuel prior to storage
Fuel	gasoline	fresh, clean gasoline		Shelf life on gasoline is 30 days; a fuel stabilizer must be used at all times
Fuel	unleaded gasoline, minimum 85 octane			Do not use any gasoline with more than 10% added ethanol. Never use E85. Do not mix oil with gasoline.

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
BATTERY PROBLEM	Battery Problem	Battery problem warning	Warning	Contact servicing dealer.
CHARGER MISSING AC	Charger Missing AC	Battery charger missing AC input	Warning
CHARGER WARNING	Charger Warning	Battery charger warning	Warning	Contact servicing dealer.
EXERCISE SET ERROR	Exercise Set Error	Exercise timer setting error	Warning
FUEL PRESSURE	Fuel Pressure	Fuel pressure warning	Warning
FUSE PROBLEM	Fuse Problem	Control panel fuse problem	Shutdown	Check ATO 7.5 amp fuse. Replace with same type fuse if bad. Contact servicing dealer if fuse is good.
HIGH TEMPERATURE	High Engine Temp.	High engine temperature alarm	Shutdown	Check ventilation around the intake, exhaust and rear of generator. Contact servicing dealer if no obstruction is found.
INSPECT BATTERY	Inspect Battery	Battery inspection reminder	Info	Inspect battery; press ENTER to clear.
INTERNAL FAULT	Internal Fault	Internal controller fault	Shutdown	Contact servicing dealer.
LOW BATTERY	Low Battery	Low battery voltage	Warning	Clear alarm. From the MAIN menu navigate to the BATTERY MENU. Contact servicing dealer if battery is GOOD. Replace battery if CHECK BATTERY is displayed.
LOW OIL PRESSURE	Low Oil Pressure	Low oil pressure alarm	Shutdown	Check oil level. Add oil per Owner's Manual. Contact servicing dealer if oil level is correct.
LOW VOLTS REMOVE LOAD	Low Volts Remove Load	Low voltage, remove load	Shutdown	Clear alarm and remove household loads from the generator. Put back in AUTO and restart.
NOT ACTIVATED	Not Activated	Unit not activated	Info	Refer to activation section in Owner's Manual.
OVER VOLTAGE	Over Voltage	Overvoltage alarm	Shutdown	Contact servicing dealer.
OVERCRANK	Overcrank	Engine failed to start after the cranking cycles	Shutdown	Check fuel line shutoff valve is in the ON position. Clear alarm. Attempt to start in MANUAL. If it does not start or starts and runs rough, contact servicing dealer.
OVERLOAD REMOVE LOAD	Overload Remove Load	Generator overloaded	Shutdown	Clear alarm and remove household loads from the generator. Put back in AUTO and restart.
OVERLOAD WARNING	Overload Warning	Overload warning	Warning
OVERSPEED	Overspeed	Engine overspeed alarm	Shutdown	Contact servicing dealer.
RPM SENSE LOSS	RPM Sense Loss	Loss of RPM sensing	Shutdown	Clear alarm and remove household loads. Put back in AUTO and restart. If problem returns, contact servicing dealer to investigate possible fuel issue.
Red Short Flash	CO Module - Red Short Flash	Elevated level of CO in the area; module is functioning properly and protecting operators	Shutdown	Generator shuts down; module is functioning as intended
SERVICE A	Service Schedule A	Schedule A maintenance due (oil, oil filter, tune-up)	Info	Perform SERVICE A maintenance; press ENTER to clear.
SERVICE B	Service Schedule B	Schedule B maintenance due (oil, oil filter, tune-up, air cleaner, spark plug(s), valve clearance)	Info	Perform SERVICE B maintenance; press ENTER to clear.
STEPPER OVER CURRENT	Stepper Over Current	Stepper motor over current	Shutdown	Contact servicing dealer.
UNDER VOLTAGE	Under Voltage	Undervoltage alarm	Shutdown	Contact servicing dealer.
UNDERSPEED	Underspeed	Engine underspeed alarm	Shutdown	Contact servicing dealer.
WIRING ERROR	Wiring Error / Miswire	Controller wiring error	Shutdown	Contact servicing dealer.

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

Procedures

Check/Adjust Valves adjustment

Tools: socket, feelers/gauges

Verify the piston is at top dead center (TDC) of its compression stroke (both valves closed).
Remove four (4) screws from rocker cover.
Remove rocker cover and rocker cover gasket.
Loosen rocker arm jam nut. Turn adjustment screw in to decrease clearance or out to increase clearance.
Hold socket steady and tighten lock nut to specification; check clearance and make minor adjustments.
After tightening jam nut, recheck valve clearance to make sure it did not change.
Install rocker cover, gasket and four screws; tighten to specifications.

Test 12 – Adjust Voltage Regulator adjustment

⚠ Ensure all material is clear of the alternator before proceeding.

Tools: VOM

Remove cover from end of alternator assembly.
Remove two screws holding down the voltage regulator (AVR).
Leave AVR connected to stator and brushes.
Set VOM to measure AC voltage.
Connect VOM across a 240VAC socket.
Set START-STOP-RUN switch to START.
Turn adjustment screw clockwise to increase voltage, counterclockwise to lower.

Test 20 - Check Spark Plugs / Test 23 - Check Valve Adjustment adjustment

Tools: feeler gauge, crow foot wrench

Adjust valve clearance with engine at room temperature
Position piston at TDC of compression stroke (both valves closed), or set intake/exhaust valve fully open method
Loosen rocker arm jam nut; turn pivot ball stud while checking clearance with a feeler gauge
When clearance is correct, hold pivot ball stud and tighten rocker arm jam nut to specified torque with a crow foot wrench
Recheck valve clearance to make sure it did not change
Install rocker arm cover with a new gasket

Test 27 - Check / Adjust Governor adjustment

Tools: AC frequency meter

Loosen governor clamp bolt
Hold governor lever at wide open throttle position
Rotate governor shaft counterclockwise (389/208/196cc) or clockwise (410cc) as far as it will go
Tighten governor lever clamp bolt to 110 in-lbs (389/208/196cc) or 70 in-lbs (410cc)
Turn speed adjustment screw counterclockwise three full turns to avoid overspeed
Start engine and let warm up under no-load
Connect AC frequency meter; no-load frequency should be 62.0-62.5 hertz
Turn speed adjust screw until frequency/RPM is within limits
Apply removable Loctite (Loctite 241) to speed adjust screw threads

Test 33 – Check Valve Adjustment adjustment

⚠ Use a new rocker arm cover gasket.

Tools: feeler gauge, allen wrench, crow's foot

Adjust valve clearance with engine at room temperature.
Position piston at TDC of compression stroke (both valves closed).
Loosen the rocker arm jam nut.
Turn pivot ball stud while checking clearance with a feeler gauge.
Hold stud with allen wrench and tighten jam nut to specified torque with a crow's foot.
Recheck valve clearance after tightening.

Test 40 – Check / Adjust Governor (389/206/163cc Engines) adjustment

⚠ Do not apply excessive torque to the governor shaft.

Tools: frequency meter

Loosen the governor lever clamp bolt.
Hold governor lever at full INC RPM; rotate governor shaft counterclockwise fully.
Tighten governor lever clamp bolt to 110 inch-pounds.
Turn speed adjustment screw counterclockwise three full turns.
Start engine and let it warm up and stabilize at no-load.
Connect frequency meter; set no-load frequency 62.0-62.5 hertz.
Add a drop of Loctite 241 to the speed adjust screw threads.

Test 41 – Check / Adjust Governor (410cc Engine) adjustment

Tools: frequency meter

Loosen the governor clamp bolt.
Hold governor lever at wide open throttle; rotate governor shaft clockwise fully.
Tighten governor lever clamp bolt to 70 inch-pounds (8 Nm).
Start generator; let it stabilize and warm up at no-load.
Connect frequency meter across generator AC output leads.
Turn the primary adjust screw to obtain a frequency of 62.5 Hz.

Trigger Pickup Adjustment (iQ) adjustment

Tools: non-metallic feeler gauge

Install or replace trigger pickup; ensure routing of wires is correct and not pinched.
With rotor in place, set gap to 0.20-0.30mm using the oval holes in the pickup bracket.
Align trigger point on rotor outside surface in-line with sensor and check/adjust gap with a non-metallic feeler gauge.
Tighten mounting screws to specification and check gap; adjust if necessary.

Valve Lash Adjustment adjustment

⚠ Hold the rocker arm jam nut in place as the pivot ball stud is turned.

Tools: Feeler gauge, 10mm Allen wrench (530cc engine), 13mm Allen wrench (410cc, 990cc, 999cc engines), Large socket and socket wrench

Engine should be cool before checking (60° to 80° F / 16° to 27° C).
Remove spark plug wires and position them away from the plugs; remove spark plugs.
Bring piston to Top Dead Center of its compression stroke (both valves closed).
Remove the four screws attaching the valve cover.
Loosen the rocker jam nut; turn the pivot ball stud while checking clearance with a feeler gauge.
Correct clearance is 0.002-0.004 inch (0.05-0.1 mm).
Hold the pivot ball stud and tighten the rocker arm jam nut to 174 in-lbs (19.68 N-m).
Recheck valve clearance to make sure it did not change.
Install new valve cover gasket and re-attach the valve cover.
Install spark plugs and re-attach the spark plug wire.
Repeat the process for the other cylinder, if necessary.

Check Engine Compression diagnostic

Tools: compression gauge

Remove spark plug.
Insert an automotive type compression gauge into spark plug hole.
Crank engine until there is no further increase in pressure; record highest reading.

Check Engine RPM diagnostic

Tools: Small engine tachometer or inductive tachometer

With engine running, connect engine tachometer per manufacturer instructions and record the engine RPM.
If engine rpm is within rated specs refer to flow chart; if outside range go to Problem 7 flowchart.

Check Fuel Pump diagnostic

⚠ Explosion and Fire. Fuel and vapors are extremely flammable and explosive. Add fuel in a well ventilated area. Keep fire and spark away.

Tools: suitable fuel container

Open side panel to expose carburetor (A) and fuel pump (B).
Carefully remove fuel line from filter on inlet side of carburetor.
Using a suitable container, slowly pull on recoil cord and turn engine over; fuel should flow from fuel line.
If fuel does not flow, verify fuel is available to pump; inspect fuel filter and pulse line.
If fuel does not flow, replace fuel pump.

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 Generac OHV?

The Generac OHV engine has an oil capacity of 1.0 liters.

What is the displacement of the Generac OHV?

The Generac OHV has a displacement of 4.2 liters with 1 cylinders.

Which generators use the Generac OHV engine?

The Generac OHV powers 17 generator set(s), including Generac CorePower 7 kW, Generac G006998-1, Generac GP1800, Generac GP3000i, Generac GP3250.

What is a common problem with the Generac OHV engine?

A commonly reported issue on generators using the Generac OHV is: No AC output.. Cause: 1. Generator is overloaded. 2. Inverter module is overheated. 3. Short circuit in electrical device. 4. Defective inverter assembly.. Fix: 1. Disconnect all loads. Shut down generator to reset module. Reduce loads, restart generator. 2. Verify service door is ON. Let cool 15 minutes by running engine without AC output. Press and hold Reset button on control panel, restart generator. 3. Verify condition of extension cords and items being powered. Press and hold Reset button on control panel. 4. Contact IASD..