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Generac NP-50G/LP Engine

Name: Generac NP-50G/LP Engine
Brand: Generac

The Generac NP-50G/LP is a 0.36 L 1-cylinder natural engine rated at 3600 rpm, producing up to 6.5 kW. It powers generator sets from Generac, including the NP-50G, NP-50LP and Q-40G. It holds 1.6 L (0.4 gal) of oil.

Also known as: Generac NP-50G/LP

0.363 L

Displacement

Cylinders

3600 rpm

Rated speed

6 kW

Gross power

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

Engine specifications

Oil capacity	1.6 L
Displacement	0.363 L
Cylinders	1
Aspiration	Natural
Rated speed	3600 rpm
Gross power	6 kW

Generator sets powered by this engine

Generac NP-50G Generac NP-50LP Generac Q-40G

How to read your Generac engine serial & model number →

Common problems

Engine won't crank.
Cause: 1. 15 amp fuse blown. 2. Loose or corroded or defective battery cables as necessary. 3. Battery is discharged or defective. 4. Defective starter contactor. 5. Defective starter motor.
Fix: 1. Replace fuse. 2. Tighten, clean or replace battery cables as necessary. 3. Recharge or replace battery. 4. Replace if defective. 5. Replace if defective.
Engine spark plug defective.
Fix: Clean, regap or replace as needed.
Engine cranks but won't start
Cause: 1. Out of fuel. 2. Fuel shutoff valve is closed. 3. Fuel pump not operating 4. Automatic choke not operating property 5. Engine is flooded. 6. Fuel Filter is clogged. 7. Defective Controller Circuit Board.
Fix: 1. Replenish fuel. 2. Open fuel shutoff valve(s). 3. Repair or replace if defective. 4. Repair, replace or adjust. 5. Wait 5-10 minutes; try again. 6. Replace filter if clogged. 7. Replace bad circuit board
Bad ignition magneto on engine.
Fix: Replace if defective.
Bad carburetor.
Fix: Adjust, repair or replace.

Compiled from service & troubleshooting documentation across every generator set that uses the Generac NP-50G/LP.

Maintenance schedule

Item	Spec	Capacity	Part #
Air filter	Paper element with foam pre-cleaner		—
Fuel filter			—
Oil filter			70185	Amazon $28.95 eBay $18.99 KuduParts $11.00
Battery	12 volt, 70 amp-hour, 360 cold cranking amperes (above 32°F); 95 amp-hour, 450 CCA (below 32°F)		—
Oil	SAE 10W-30, For Service SF	1.5 U.S. quarts	—
Spark plug	Champion RC12YC		RC12YC	Amazon $19.99 eBay $12.90 FridayParts $19.99

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
Engine oil level	Check	8 hr		At least every eight hours of operation, or before use
25-hour check up	Other	25 hr		First service — After 25-hour break-in: change oil and oil filter, check oil level, inspect cooling/ventilation openings, check carburetor adjustments, check ignition system, inspect electrical system, inspect exhaust system
Foam pre-cleaner	Clean	25 hr	3 mo	Every three months or 25 operating hours, whichever comes first; more often in dusty conditions
Engine crankcase oil	Change	50 hr		First service — First change after 25-hour break-in period, then every 50 operating hours
Engine oil	Change	50 hr		First service — Thereafter every 50 operating hours; more often under heavy load or high ambient temperature
Air intake screen	Clean	100 hr		At least once every 100 hours of operation; clean more often if necessary
Engine spark plug	Clean	100 hr		Clean and set gap to 0.030 inch (0.76mm) every 100 hours
Fuel filter	Replace	100 hr	12 mo	Every 100 hours of operation or once each year, whichever comes first
Oil filter	Change	100 hr		First service — First change after 25 hours, every 100 operating hours thereafter
Paper air filter	Replace	100 hr	12 mo	Once each year or every 100 hours, whichever comes first; must be flame retardant type
Paper air filter element	Replace	100 hr	12 mo	Once each year or every 100 hours of operation, whichever comes first
Battery	Test		6 mo	Every six months check state of charge and condition with an automotive battery hydrometer
Battery state of charge and condition	Test		6 mo	Every six months with automotive type battery hydrometer

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 system clearance to combustible material	3	inches (76mm)
Clearance	Generator compartment clearance on sides	1	inch
Clearance	Generator compartment clearance on top	1-1/2	inches
Gap	Spark plug gap	0.030	inch (0.76mm)
Other	Battery amp-hour rating	70	amp-hour	above 32°F (0°C)
Other	Battery amp-hour rating	95	amp-hour	below 32°F (0°C)
Other	Battery charge current	2	amperes (max)
Other	Battery grounding	Negative (-)
Other	Battery voltage	12	volts DC
Other	Battery voltage drop	0.12	volts per 100 amperes
Other	Cold cranking amperes	360	CCA	above 32°F (0°C)
Other	Cold cranking amperes	450	CCA	below 32°F (0°C)
Other	Compression ratio	8.6 to 1
Other	Crankcase oil capacity	1.5	U.S. quarts (1.6 liters)
Other	Cranking current	100	DC amperes
Other	Displacement	363	cc
Other	Displacement	480	cc
Other	Displacement	570	cc
Other	Exhaust temperature rise maximum	117	°F (65°C) above ambient
Other	Flexible fuel hose length	6	inches longer than necessary
Other	Fuel line clearance from exhaust	2	inches
Other	Fuel octane	87	minimum octane rating	gasoline
Other	LP gas connection size	3/4	inch (female)
Other	Minimum cooling air inlet opening	100	square inches
Other	Minimum gas flow rate	67	cubic feet per hour
Other	Rated horsepower	13	horsepower	at 3600 RPM
Other	Rated horsepower	16	horsepower	at 3600 RPM
Other	Rated horsepower	19	horsepower	at 3600 RPM
Pressure	LP gas pressure at gaseous fuel solenoid valve and secondary regulator inlet	11	inches water column	operating
Pressure	LP gas pressure at inlet to gaseous fuel solenoid	11	inches water column
Pressure	LP gas pressure maximum	14	inches water column	do not exceed
Pressure	Leak test pressure	90	psi (620kPa)
Pressure	Low oil pressure switch	10	PSI	normally-closed; engine shuts down on low pressure
Pressure	Oil pressure switch (low oil) setting	10	PSI	normally-closed
Speed	Engine RPM	2570	rpm
Speed	Engine RPM	2571	rpm
Speed	Engine RPM	2700	rpm
Speed	Frequency under load	58	Hertz	minimum under load
Speed	Frequency under load minimum	58	Hz	under load
Speed	No-load frequency	62	Hz	no-load
Speed	Rated horsepower	15	HP	at 4200 RPM
Speed	Rated horsepower engine speed	4200	RPM	15 HP rated
Speed	Rotor RPM	3600	RPM
Temperature	High oil temperature switch	284	°F (140°C)
Temperature	High oil temperature switch closes	284	°F (140°C)
Temperature	High temperature shutdown switch	284	°F (140°C)	contacts close and engine shuts down
Temperature	High temperature shutdown switch setting	284	°F (140°C)	shutdown
Torque	Governor clamp bolt	70	inch-pounds (8 N-m)
Torque	Governor clamp nut	70	inch-pounds (8 N-m)
Voltage	Battery cable voltage drop	0.12	volts per 100 amperes of cranking current	maximum
Voltage	Battery charge voltage	14	Volts DC
Voltage	Dual voltage line-to-line no-load voltage	244-252	volts AC	no-load, reconnected dual voltage
Voltage	No-load voltage	122-126	volts AC	no-load
Voltage	Regulated AC output voltage	120	volts AC	at 60 Hz (voltage-to-frequency ratio 2-to-1)
Voltage	Voltage regulator adjustment	124	volts	62 Hz, no-load
Voltage	Voltage regulator setting	124	volts AC	at 62 Hz no-load

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	SAE 10W-30	For Service SF	1.5 U.S. quarts	1.6 liters
Engine oil	SAE 30 (summer); SAE 10W-30 acceptable substitute; SAE 5W-30 (winter)	API service classification SF, SG or SH	1.4 liters	Crankcase and oil filter capacity about 1400ml or about 1.5 U.S. quarts. Do not use SAE 10W-40. Use no special additives.
Engine oil	SAE 30 (summer); SAE 5W30 (winter); SAE 10W-30 acceptable substitute in summer	API service classification SF, SG, or SH	1.4 L	DO NOT USE SAE 10W40. Crankcase and oil filter capacity about 1400ml or about 1.5 U.S. quarts. Use no special additives. For storage, use SAE 10W30, API 'For Service SF'.
Fuel	Commercial propane gas			Vapor withdrawal type system only
Fuel	High quality UNLEADED gasoline (leaded REGULAR grade acceptable substitute)			Gasoline with alcohol must not contain more than 10 percent ethanol; do not use methanol
Fuel	High quality unleaded gasoline; leaded REGULAR grade an acceptable substitute			Do not use gasoline containing alcohol; if used, must not contain more than 10 percent ethanol and must be removed during storage. Do NOT use gasoline containing methanol.
Fuel	UNLEADED gasoline, minimum octane rating 87			Leaded REGULAR grade gasoline acceptable substitute. For gasoline-powered units.
Fuel	Unleaded gasoline with minimum octane rating of 87			Leaded REGULAR grade gasoline is an acceptable substitute
Other	Distilled water (battery cells)			DO NOT USE TAP WATER IN BATTERY

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

Procedures

Adjusting No-Load Frequency (NP-50G/LP) adjustment

⚠ Avoid overspeeding the engine.

Tools: Pliers, Wrench

Loosen governor clamp bolt.
Push spring end of governor lever clockwise to wide open throttle position.
Hold governor lever at wide open throttle. With pliers, rotate governor shaft fully counterclockwise.
While holding shaft fully clockwise and lever at wide open throttle, tighten governor clamp bolt to 70 inch-pounds (8 N-m).
Start engine, let it stabilize and warm up at no-load.
Turn adjuster nut to obtain frequency reading of 62 Hertz.
Check governor spring location in slot of governor lever. Move spring down one slot for excessive droop; up one slot for greater stability.
After repositioning spring, recheck frequency and readjust adjuster nut if necessary.
Check AC voltage reading. If incorrect, voltage regulator may require adjustment.

Adjusting No-Load Frequency (Q-40G, NP-66G/LP, Q-55G/LP, Q-70G/LP) adjustment

⚠ Avoid overspeeding the engine.

Tools: Screwdriver, Wrench

Loosen governor clamp nut.
Push spring end of governor lever all the way up to wide open throttle position.
Hold governor lever at wide open throttle. Insert screwdriver into slotted end of governor shaft. Rotate governor shaft fully counterclockwise.
While holding governor shaft fully counterclockwise and lever at wide open throttle, tighten governor clamp nut to 70 inch-pounds (8 N-m).
Start engine, let it stabilize and warm up at no-load.
Turn adjuster nut to obtain frequency reading of 62 Hertz.
Check governor spring location. Move spring left on bracket teeth for excessive droop; right for greater stability.
After repositioning spring, recheck frequency and readjust adjuster nut if necessary.
Check AC voltage reading. If incorrect, voltage regulator may require adjustment.

Adjusting No-Load Frequency for NP-50G/LP adjustment

Tools: pliers

Loosen governor clamp bolt.
Push spring end of governor lever clockwise to wide open throttle position of lever.
Hold governor lever at wide open throttle and, with pliers, rotate governor shaft fully counterclockwise.
While holding governor shaft fully clockwise and governor lever at wide open throttle, tighten governor clamp bolt to 70 inch-pounds (8 N-m).
Start engine; let it stabilize and warm up at no-load.
Turn adjuster nut to obtain a frequency reading of 62 Hertz.
Check governor spring location in slot of governor lever.
If droop is excessive, move governor spring down one slot on lever.
For greater stability, move governor spring up one slot on lever.
Recheck frequency reading; readjust adjuster nut if necessary to obtain 62 Hertz at no-load.
When frequency is correct at no-load, check AC voltage; voltage regulator may require adjustment.

Adjusting No-Load Frequency for Q-40G, NP-66G/LP, Q-55G/LP, Q-70G/LP adjustment

Tools: screwdriver

With engine stopped, inspect anti-lash spring. Replace if broken or damaged; attach if disconnected.
Loosen governor clamp nut.
Push spring end of governor lever all the way up to wide open throttle position.
Hold governor lever at wide open throttle and insert screwdriver into slotted end of governor shaft.
Rotate governor shaft fully counterclockwise (CCW).
While holding shaft fully counterclockwise and lever at wide open throttle, tighten governor clamp nut to 70 inch-pounds (8 N-m).
Start engine; let it stabilize and warm up at no-load.
Turn adjuster nut to obtain a frequency reading of 62 Hertz.
Check governor spring location in notched teeth of governor adjustment bracket.
If droop is excessive, move governor spring to the left on notched teeth of bracket.
For greater stability, move governor spring to the right on notched teeth of bracket.
Recheck frequency reading; readjust adjuster nut if necessary to obtain 62 Hertz at no-load.
When frequency is correct at no-load, check AC voltage; voltage regulator may require adjustment.

Voltage Regulator Adjustment adjustment

Tools: screwdriver

Remove generator control panel cover and front panel.
With frequency at 62 Hertz, AC voltage should read 124 volts.
If voltage is incorrect, slowly turn VOLTAGE ADJUST POT on voltage regulator until AC voltage is correct.

Checking No-Load Voltage and Frequency diagnostic

Tools: AC voltmeter, AC frequency meter

Connect an accurate AC voltmeter and AC frequency meter across generator AC output leads.
With generator running, stabilized, and warm, check AC frequency and voltage. Frequency should be about 62 Hz; voltage about 122-126 volts AC.
If frequency is high or low, adjust engine governor to obtain 62 Hertz at no-load; then recheck voltage reading.
If frequency is good but voltage is high or low, adjust voltage regulator to obtain 124 volts at 62 Hz no-load.

LP Gas Leakage Test diagnostic

⚠ Do not use any flame to test for leaks.

⚠ No leakage is permitted.

Tools: separate 12 volts DC source, soap and water or equivalent solution

Use a separate source of 12 volts DC to open the gaseous fuel solenoid valve.
Test all connections, hoses, valves, regulators, fittings, and other fuel system parts under gas or air pressure of not less than 90 psi (620 kPa).
Use soap and water or equivalent solution to check for leaks.
Do not use any flame to test for leaks.
Comply with NFPA Paragraph 318.

Leakage Tests diagnostic

⚠ Do not use any flame to test for leaks.

Tools: Soap and water solution, 12 volts DC source

Do not place generator into service until gas system properly tested for leaks.
Use separate source of 12 volts DC to open gaseous fuel solenoid valve.
Test all connections, hoses, valves, regulators, fittings under gas or air pressure of not less than 90 psi (620kPa).
Use soap and water or equivalent solution to check for leaks.
Do not use any flame to test for leaks.

Testing Under Load diagnostic

Tools: AC frequency meter

Apply electrical loads equal to about 75-100% of unit's rated wattage/amperage capacity.
Check frequency with electrical load applied; frequency should not drop below about 58 Hz under load.
Let unit run at least 30 minutes with load applied; check unit is not running excessively hot and adequate cooling air flow is available.
Do not allow unit to overheat during prolonged operation.

Battery Cable Connections installation

Connect battery cable from battery POSITIVE, POS or (+) post to large lug on starter contactor.
Connect battery cable from battery NEGATIVE, NEG or (-) post to frame ground connection.
Connect cables so connectors are clean and tight. Check battery cable boot for starter cable has been installed.

Reconnection Procedure installation

⚠ Units reconnected for 120/240 volts dual voltage output will not be listed per RVIA.

⚠ Not applicable to Q-40G model.

Remove generator cover and front panel.
Disconnect stator leads 11 and 33, T1 (red) and T3 (black) from main circuit breakers CB1 and CB2.
Set aside leads T1 (red) and T3 (black) for later use.
Disconnect stator leads 11 and 33 from 4-tab terminal connector (TC).
Disconnect stator leads 22 and 44 from grounding terminal (GT).
Disconnect one of the two T2 (white) leads from grounding terminal.
Remove existing circuit breakers CB1 and CB2; install new appropriately rated circuit breaker.
Connect stator leads 11 and 44 to new circuit breaker; attach leads T1 (red) and T3 (black).
Connect stator leads 22 and 33 to grounding terminal (GT).
Be sure a neutral lead is installed and routed from grounding terminal for connection loads.
Route leads T1 (red), T3 (black), and grounded neutral lead through conduit clamp and out of panel.
Reassemble panel and generator cover.

Reconnection for Dual Voltage installation

⚠ Units reconnected for 120/240 volts dual voltage output will not be listed per RVIA.

⚠ Not applicable to Q-40G model.

Tools: Screwdriver, Pliers

Gain access to generator panel interior by removing generator cover and front panel.
Disconnect stator leads 11 and 33, T1 (red) and T3 (black) from main circuit breakers CB1 and CB2. Set aside T1 and T3.
Disconnect stator leads 11 and 33 from the 4-tab terminal connector (TC).
Disconnect stator leads 22 and 44 from the grounding terminal (GT).
Disconnect one of the two T2 (white) leads from the grounding terminal.
Remove existing circuit breakers CB1 and CB2. Install new appropriately rated circuit breaker.
Connect stator leads 11 and 44 to new circuit breaker. Attach leads T1 (red) and T3 (black) to circuit breaker.
Connect stator leads 22 and 33 to grounding terminal (GT).
Be sure a neutral lead is installed and routed from grounding terminal for connection loads.
Route leads T1 and T3 and grounded neutral lead through conduit clamp and out of panel.
Reassemble panel and generator cover.
Loads may be connected: T3 to Neutral 120 volts; T1 to Neutral 120 volts; T1 to T3 240 volts.

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
120	1	T1 (red) to Neutral	T1, neutral	After dual voltage reconnection.
120	1	T1 (red) to T2 (white)	T1, T2	Line-to-neutral; protected by circuit breaker CB1; up to 3600 watts.
120	1	T1 (red) to T2 (white) neutral	T1, T2	Protected by circuit breaker CB1; use separately for 120 volts, 1-phase, 60 Hz loads up to 3600 watts (3.6 kW).
120	1	T3 (black) to Neutral	T3, neutral	After dual voltage reconnection.
120	1	T3 (black) to T2 (white)	T3, T2	Line-to-neutral; protected by circuit breaker CB2.
120	1	T3 (black) to T2 (white) neutral	T3, T2	Protected by circuit breaker CB2; total unit load must not exceed maximum rating.
120	single	Figure 1 - Connections for 120 Volts Only	dual 2-wire connection system; neutral grounded	Dual stator AC power windings; generator may have been installed to power 120 volts AC loads
120/240	1	Stator leads 11 and 44 to new circuit breaker; 22 and 33 to grounding terminal	11, 44, 22, 33	Reconnection procedure for dual voltage output.
120/240	1	Stator leads 11 and 44 to new circuit breaker; stator leads 22 and 33 to grounding terminal	11, 44, 22, 33	Dual voltage reconnection procedure. Not applicable to Q-40G.
120/240	single	Dual voltage - install jumper wire between the circuit breakers when reconnecting		All units are reconnectable to 120 and/or 240 volts dual voltage output; units are no longer listed per RVIA/ANSI when reconnected for dual voltage output. Refer to the Installation Manual.
240	1	T1 (red) to T3 (black)	T1, T3	Dual voltage; neutral T2.
240	1	T1 to T3	T1, T3	After dual voltage reconnection. Replace CB1 and CB2 with a single suitably rated circuit breaker.

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 NP-50G/LP?

The Generac NP-50G/LP engine has an oil capacity of 1.6 liters.

What is the displacement of the Generac NP-50G/LP?

The Generac NP-50G/LP has a displacement of 0.363 liters with 1 cylinders.

Which generators use the Generac NP-50G/LP engine?

The Generac NP-50G/LP powers 3 generator set(s), including Generac NP-50G, Generac NP-50LP, Generac Q-40G.

What is a common problem with the Generac NP-50G/LP engine?

A commonly reported issue on generators using the Generac NP-50G/LP is: Engine won't crank.. Cause: 1. 15 amp fuse blown. 2. Loose or corroded or defective battery cables as necessary. 3. Battery is discharged or defective. 4. Defective starter contactor. 5. Defective starter motor.. Fix: 1. Replace fuse. 2. Tighten, clean or replace battery cables as necessary. 3. Recharge or replace battery. 4. Replace if defective. 5. Replace if defective..