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Generac GN-190 or GN-220 Engine

Name: Generac GN-190 or GN-220 Engine
Brand: Generac

The Generac GN-190 or GN-220 is a 1-cylinder engine. It powers generator sets from Generac, including the NP-30G and NP-40G.

Also known as: Generac Corporation GN-190 or GN-220

Part of the Generac GN-190 engine family — 4 variants share parts & fitment.

Cylinders

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

Engine specifications

Cylinders	1

Generator sets powered by this engine

Generac NP-30G and NP-40G

How to read your Generac engine serial & model number →

Common problems

Stator windings are shorted to ground
Fix: The Stator should be cleaned and dried. The Insulation resistance tests should then be repeated. If, after cleaning and drying, the Stator again falls the test, replace the Stator assembly.
If the engine starts but the Stepper Motor does not move, and shutdown occurs after several seconds
Cause: Broken or shorted Power Supply winding (Wires PS1 and PS2)
If the engine shuts down but speed did NOT exceed 4500 rpm
Cause: One of the main windings (Power Phase 1 or 2) Is open
A short between windings exists
Fix: Clean and dry the Stator. Then, repeat the tests. If Stator falls a second test (after cleaning and drying), replace the Stator assembly.

Compiled from service & troubleshooting documentation across every generator set that uses the Generac GN-190 or GN-220.

Service intervals

Item	Action	Hours	Months	Notes
Air cleaner paper filter	Clean	25 hr	12 mo	Clean or replace every 25 hours or once each year, whichever comes first; replace if extremely dirty
Air cleaner paper filter	Replace	25 hr	12 mo	Every 25 hours or once each year, whichever comes first
Engine oil	Change	50 hr		First service — Thereafter, every 50 operating hours
Oil filter	Change	50 hr		First service — Thereafter, every 50 operating hours
Fuel filter	Replace	100 hr	12 mo	Every 100 hours of operation or once each year, whichever occurs first
Spark plug	Clean	100 hr		Clean and reset gap to 0.030 inch (0.76mm) every 100 hours; do not blast clean
Spark plug gap	Adjust	100 hr		Reset to 0.030 inch (0.76mm)

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	Carburetor throttle lever stop tab to stop block gap	0.003	inch
Gap	Spark plug gap	0.030	inch
Other	Ignition timing	29 degrees BTDC (at higher speeds); 15-18 degrees BTDC at cranking speeds	degrees BTDC
Other	Minimum acceptable Stator insulation resistance	rated volts/1000 + 1	megohm
Pressure	Engine compression pressure, minimum allowable	55	psi	while cranking, cold engine
Pressure	Engine compression pressure, nominal	60	psi	while cranking, cold engine
Pressure	Fuel pump pressure at zero delivery	2.0 to 3.5	psi
Pressure	LP gas inlet pressure to lockoff solenoid / secondary regulator	11	inches water column
Pressure	Low oil pressure switch set point	5	psi
Pressure	Oil pressure relief valve opening	30	psi
Resistance	Fuel pump coil	0.75 to 1.00	ohm
Resistance	Genistor COM to G1/G2/G3/G4	20-60	ohm
Resistance	Ignition coil primary	0.5 to 1.5	ohm
Resistance	Ignition coil secondary	16,000-17,000	ohm
Resistance	Stator battery charge windings (66 to 55; 77 to 55)	0.037-0.042	ohm
Resistance	Stator power phase windings (Lead AC1/AC2/SL1/SL2 to 11)	0.30 to 0.42	ohm
Resistance	Stator power supply winding (PS1 to PS2)	0.35 to 0.44	ohm
Resistance	Stator timing winding (TIM1 to TIM2)	0.35 to 0.44	ohm
Resistance	Stepper motor windings (RED to ORANGE/YELLOW/BROWN/BLACK)	19-21	ohm
Speed	NP-30G engine speed at 0 A load (113-121 VAC)	2250-2800	rpm
Speed	NP-30G engine speed at 10 A load (113-121 VAC)	2700-3300	rpm
Speed	NP-30G engine speed at 25 A load (115-124 VAC)	3300-4000	rpm
Speed	NP-40G engine speed at 0 A load (113-121 VAC)	2250-2800	rpm
Speed	NP-40G engine speed at 10 A load (113-121 VAC)	2750-3300	rpm
Speed	NP-40G engine speed at 20 A load (117-121 VAC)	3150-3750	rpm
Speed	NP-40G engine speed at 30 A load (109-124 VAC)	3500-4000	rpm
Torque	Carburetor to intake elbow	5	ft-lb
Torque	Connecting rod cap bolts	10	ft-lb
Torque	Cylinder head bolts	25	ft-lb
Torque	Cylinder head bolts	29	ft-lb
Torque	Flywheel nut	75	ft-lb
Torque	Ignition coil mount bolts	18	ft-lb
Torque	Intake elbow	5	ft-lb
Torque	Rocker arm jam nut	6.3	ft-lb
Torque	Rocker arm jam nut	75	inch-pounds
Torque	Rocker arm pivot ball	3.8	ft-lb
Torque	Spark plug	13	ft-lb
Torque	Sump cover bolts	100	lb-in
Valve clearance	Exhaust valve	0.001-0.003	inch	cold, engine at room temperature, piston at TDC of compression stroke
Valve clearance	Exhaust valve	0.0018-0.003	inch	cold, engine at room temperature, piston at TDC of compression stroke
Valve clearance	Intake valve	0.001-0.0022	inch	cold, engine at room temperature, piston at TDC of compression stroke
Valve clearance	Intake valve	0.001-0.003	inch	cold, engine at room temperature, piston at TDC of compression stroke

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	SAE 30 (with filter change)			946.0 ml	Engine crankcase oil capacity with oil filter change is about 1 U.S. quart (946 ml)
Engine oil	SAE 5W-20 or SAE 5W-30	For Service SC, SD, SE, SF or SG	below 0°C		Winter months (below 32 F / 0 C); do not use SAE 10W-40
Engine oil	SAE 30	For Service SC, SD, SE, SF or SG	above 0°C	850.0 ml	Summer months (above 32 F / 0 C); SAE 10W-30 is an acceptable substitute; capacity without oil filter change is about 29 fluid ounces (850 ml)
Fuel	LP gas (vapor withdrawal only)				Gaseous fuel systems; generator requires at least 67 cubic feet of gas per hour
Fuel	Unleaded regular gasoline				Gasoline fuel systems; leaded regular acceptable substitute; gasohol not recommended (max 10 percent ethanol); do not use methanol; 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.

Procedures

Carburetor Idle Jet Adjustment adjustment

⚠ Do NOT adjust the fuel-air mixture excessively lean; an excessively lean mixture can result in engine damage.

Turn the idle jet inward (clockwise) until it just contacts its seat; do not force.
Turn the idle jet outward (counterclockwise) 1-1/8 turns.
Start the engine and let it warm up for about five (5) minutes.
With engine running at no-load, turn the idle jet clockwise (leaner) until engine speed starts to decrease or fluctuate.
Turn the idle jet counterclockwise (richer) until engine speed decreases or black smoke comes from the exhaust.
Very slowly turn the idle jet clockwise (leaner) until engine speed just stabilizes or black smoke just stops.

Valve Clearance Adjustment adjustment

Tools: Allen wrench, feeler gauge, torque wrench, crow's foot

Rotate the crankshaft until the piston is at top dead center (TDC) of its compression stroke; both valves should be closed.
Loosen the rocker arm jam nut.
Use an Allen wrench to turn the pivot ball stud while checking clearance between rocker arm and valve stem with a feeler gauge.
When clearance is correct, hold the pivot ball stud with the Allen wrench while tightening the jam nut with a crow's foot.
Recheck the valve clearance after tightening the jam nut.

Spark Test (Ignition System) diagnostic

Tools: spark tester

Disconnect the high tension lead from the spark plug.
Attach the spark plug high tension lead to the spark tester terminal.
Connect the spark tester clamp to the engine cylinder head.
Crank the engine rapidly; the engine must be turning at 350 rpm or more.
If spark jumps the tester gap, the ignition system is operating satisfactorily.

Testing the Battery Charge Circuit diagnostic

Tools: VOM

Disconnect Wire 77 at the Battery Charge Rectifier (BCR).
Disconnect Stator output Wire 66 at the BCR.
Disconnect Wire 55.
Set a VOM to its Rx1 scale and zero the meter.
Connect the VOM test leads across Wires 77 and 55, then across Wires 66 and 55; note the resistance.
With the unit running, measure AC voltage at the Wires 66 and 77 terminals of the BCR.
With the engine running, check for DC voltage between the BCR Wire 55 and frame ground; if AC was present but DC is not, replace the BCR.

Testing the Fuel Lockoff Solenoid diagnostic

Tools: VOM

Set a volt-ohm-milliammeter (VOM) to read battery voltage (12 VDC).
Connect the VOM test leads across Wire 14 (Red) at the solenoid and a clean frame ground.
Set the fuel primer switch on the generator panel to its ON position.
The meter should indicate battery voltage and the solenoid should energize open.

Testing the Genistor diagnostic

⚠ Do not test the Genistor until all leads have been disconnected.

Tools: VOM

Disconnect all wires from the Genistor before attempting to test it.
Set a VOM to a resistance scale that will allow a range of about 20-60 ohms and zero the meter.
Connect one test lead to the COM terminal and the other to Terminals G1, G2, G3 and G4 one at a time; each should read 20-60 ohms.
Set the VOM to Rx1 and check continuity across the COM terminal and the center screw.
Check continuity across AC1, AC2, SL1 and SL2 screw to their respective terminals.
Set the VOM to Rx10,000 and verify no continuity between any of the screws; replace the Genistor if it fails any test.

Testing the Stepper Motor diagnostic

Tools: VOM

Unplug the Stepper Motor connector from its receptacle on the CCG circuit board.
Set a VOM to its Rx1 scale and zero the meter.
Connect one probe to the RED wire pin (+DC); connect the other probe to the ORANGE, YELLOW, BROWN and BLACK pins one at a time; each should read about 19-21 ohms.
Set the VOM to Rx10,000 and connect one probe to the RED wire pin, the other to the motor case; the meter should read infinity.
Replace the Stepper Motor if it fails any part of the test.

Engine Storage Preparation maintenance

⚠ Drain the oil while the engine is still warm

Start the engine and let it warm up.
After the engine is thoroughly warmed up, shut it down. If gasohol was used, turn off the fuel supply and let it run out of gas.
While the engine is still warm, completely drain the oil, then refill with recommended oil.
Attach a tag to the engine indicating the viscosity and classification of the oil in the crankcase.
Remove the spark plug and pour about one (1) ounce (15ml) of clean engine oil into the spark plug opening; crank several times; install and tighten the spark plug.
Remove the battery and store it in a cool, dry room on a wooden board; never store on a concrete or wood floor.
Clean and wipe the generator exterior surfaces.

Engine Tuneup maintenance

Tools: torque wrench, feeler gauge

Service and repair engine air cleaner as necessary.
Check engine oil level and condition; add or change oil as required.
Remove shrouding and clean away dirt from the engine cylinder head and cooling fins.
Check fuel filters and clean or replace as necessary.
Replace the spark plug with a Champion RC12YC (or equivalent) plug; set gap to 0.030 inch (0.76mm).
Install new plug and tighten to 13 foot-pounds (1.8 N-m).
Check that wiring is free of breaks and abrasions and is properly routed.
Check for spark as outlined in the Ignition section.
Run engine, adjust carburetor if necessary and check operation.

Return Unit to Service After Storage maintenance

Verify that the correct oil is in the engine crankcase by checking the tag on the engine.
Check the battery; fill all cells to proper level with distilled water (do not use tap water); recharge or replace if necessary.
Turn off all electrical loads. Start the engine at no-load and let it warm up.
Apply electrical loads to at least 50% of the unit's rated capacity.
When the engine is thoroughly warmed up, turn off or disconnect all electrical loads, then shut the engine down.

Stator Insulation Resistance Test test

⚠ The high voltages used in testing insulation resistance will damage electronic components; isolate all Stator leads before testing.

Tools: HI-Pot tester or Megohmmeter

Disconnect and isolate all Stator leads from other components.
Connect the ends of all Stator leads together; make sure none touch any terminal or part of the generator.
Connect one tester probe to the junction of all Stator leads; connect the other probe to a clean frame ground on the Stator.
Apply a voltage of 1000 volts for about 1 second.
Observe the breakdown indicator or read the megohms of resistance.

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

Connection	Leads	Notes
Battery Charge Rectifier (BCR)	66 (Brown)
CCG Circuit Board (CONN4)	PS1 (Brown)	Pin 1 of CONN4 connector
Engine Controller Board (J1 pin 1)	56	Delivers 12 VDC to Starter Contactor while cranking only
Genistor (G)	SL2 (Brown)
Grounding Terminal	77 (Brown)
Ignition Sensor	RED (+)	Battery voltage from Ignition Module to Ignition Sensor
Main Circuit Breaker (CB1)	11 (Blue)

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

Parts cataloged across the Generac GN-190 family

Part #	Description	Category
78601	ELEMENT, AIR FILTER	air_filter
86311	FUEL FILTER	fuel_filter
78629	GASKET, BREATHER	gasket
78631	GASKET, CARBURETOR/SKIRT	gasket
87478	GASKET, OIL FILTER ADAPTOR	gasket
89096	GASKET, CRANK CASE FLANGE	gasket
89476	GASKET, EXHAUST	gasket
90051	GASKET, CARB/SPACER/HEAD	gasket
90536	GASKET, AIR CLEANER OUTLET	gasket
94643	GASKET, OIL DRAIN PLUG	gasket
96362	GASKET, ROCKER COVER	gasket
96459	GASKET, CARB/INLET/ADAPTOR	gasket
A8822	GASKET, CYLINDER HEAD	gasket
30340	1/4" FUEL LINE (8" LONG)	hose
82580D	3/16" CARBURETOR LINE (4" LONG)	hose
86710	HOSE, CARBURETOR INLET	hose
89062	HOSE, BREATHER	hose
70185	FILTER, OIL	oil_filter
52617	DRAIN PLUG, M12 x 1.75" LONG	other_service
65795	Battery Charge Rectifier	other_service
77604	HOUR METER	other_service
86275	GENISTOR, TRIAC MODULE	other_service
86711	MODULE, IGNITION	other_service
86714	SCREEN, OIL PICK-UP	other_service
86730	TUBE, EXHAUST OUTLET	other_service
86731A	ASSEMBLY, MUFFLER	other_service
89049B	COIL, IGNITION	other_service
89680	SPARK ARRESTOR	other_service
90145	30A Circuit Breaker (all units); 30A Circuit Breaker Q-70G	other_service
90881A	ASSEMBLY, CARBURETOR	other_service
92234	RV CONTROL BOARD	other_service
94468-A	Manual Part No. 94468-A	other_service
A961	FUSE, 7.5A. AGC	other_service
A9969	ASSEMBLY, PCB CCG	other_service
90475	FUEL PUMP	pump
81695	SEAL, OIL-CRANKSHAFT	seal
88156	SEAL VALVE-INTAKE	seal
89045	SEAL, WASHER EXH. PIPE	seal
89048	SEAL, OIL FILTER HOLE	seal
90071	O-RING, 1.062" I.D.	seal
90072	O-RING .562" I.D.	seal
60108	GASKET, OIL FILTER SUPPORT	sensor
77667	Oil Pressure Switch	sensor
86697	ASSEMBLY IGNITION SENSOR	sensor
94090	SWITCH-THERMAL, OIL TEMP.	sensor
72347	SPARK PLUG-CHAMPION R12YC	spark_plug

Parts cataloged across all variants of this engine family — verify the exact part fits your specific variant and serial number before ordering.

Common questions

Which generators use the Generac GN-190 or GN-220 engine?

The Generac GN-190 or GN-220 powers 1 generator set(s), including Generac NP-30G and NP-40G.

What is a common problem with the Generac GN-190 or GN-220 engine?

A commonly reported issue on generators using the Generac GN-190 or GN-220 is: Stator windings are shorted to ground. Fix: The Stator should be cleaned and dried. The Insulation resistance tests should then be repeated. If, after cleaning and drying, the Stator again falls the test, replace the Stator assembly..