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Generac 480c Engine

The Generac 480c is a 0.66 L engine. It powers generator sets from Generac, including the POWERPACT 55, POWERPACT 66, POWERPACT 70 and QuietPact 55.

Also known as: Generac 480c

0.66 L

Displacement

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

Engine specifications

Displacement	0.66 L

Generator sets powered by this engine

Generac POWERPACT 55Generac POWERPACT 66Generac POWERPACT 70Generac QuietPact 55

How to read your Generac engine serial & model number →

Common problems

Engine cranks but will not start — spark plug is wet
Cause: Overchoking
Engine cranks but will not start — spark plug is dry
Cause: Leaking carburetor mounting gaskets
Engine starts hard or will not start
Cause: Physical damage to the AC generator; check the Rotor for contact with the Stator
Voltage & frequency are both high or low
Fix: Go to Test 2 (Check Engine Governor)
Problem continues after adjusting valves to specification
Cause: Valve clearance out of adjustment
Fix: Adjust valves to specification and retest; if problem continues, go to Test 38
No-load voltage and frequency are within the stated limits
Fix: Go to Test 13
Hard starting or failure to start
Cause: Flywheel key sheared or partially sheared, changing ignition timing
Fix: Remove and inspect flywheel key for damage
Governed speed is high or low, causing AC frequency and voltage to be correspondingly high or low
Cause: Governor out of adjustment
Fix: Loosen the GOVERNOR CLAMP BOLT; push Spring end of GOVERNOR LEVER clockwise to wide open throttle position of lever; hold the GOVERNOR LEVER at wide open throttle and, with a pair of pliers, rotate the GOVERNOR SHAFT fully clockwise (CW) using a minimum amount of force against the governor shaft; while holding the GOVERNOR SHAFT fully clockwise and the GOVERNOR LEVER at wide open throttle, tighten the GOVERNOR CLAMP BOLT to 70 inch-pounds (8 N-m); start engine, let it stabilize and warm up at no-load; turn the ADJUSTER NUT to obtain a frequency reading of 62 Hertz; if droop is excessive, move the GOVERNOR SPRING down one slot on LEVER; for greater stability, move the GOVERNOR SPRING up one slot on LEVER; after repositioning the SPRING on a LEVER slot, recheck frequency reading and, if necessary, readjust ADJUSTER NUT to obtain 62 Hertz at no-load; when frequency is correct at no-load, check the AC voltage reading and if voltage is incorrect, the voltage regulator may require adjustment
Generator produces zero voltage or residual voltage (5-12 VAC)
Fix: Go to Test 3 (Test Excitation Circuit Breaker)
ENGINE WILL NOT CRANK 7.5 AMP (F1) FUSE BLOWING
AC voltage and frequency are BOTH correspondingly high or low
Fix: Go to Test 2
AC output voltage drops to a value commensurate with the Rotor's residual magnetism (about 5-12 volts AC)
Cause: Excitation circuit breaker (CB3) failed in its open position
Fix: Replace the excitation (DPE) circuit breaker (CB3), and go to Test 4
AC output voltage and frequency are both "zero"
Fix: Go to Test 12
AC frequency is good but low or residual voltage is indicated
Fix: Go to Test 3
7.5 amp fuse blowing F1

Compiled from service & troubleshooting documentation across every generator set that uses the Generac 480c.

Service intervals

Item	Action	Hours	Months	Notes
Engine Oil Level	Check	8 hr		At least every eight hours of operation, or before use
Foam Precleaner	Clean	25 hr	3 mo	Every three months or every 25 hours, whichever occurs first
Spark Arrestor	Clean	50 hr		Inspect and clean every 50 hours or once each year, whichever comes first
Air Pre-filter	Clean	100 hr		From RV Generator Service Interval list
Engine Oil and Oil Filter	Change	100 hr		First service — Every 100 operating hours; more often under heavy load or high ambient temperature
Spark Plug	Clean	100 hr		Clean plug and reset gap every 100 hours
Spark Plugs	Inspect	100 hr		RV Generator Service Interval list
Paper Air Filter Element	Replace	250 hr
Fuel Filter	Replace	400 hr		Gasoline only; once each year or every 400 hours, whichever comes first
Spark Plugs	Replace	500 hr
Valve Lash	Adjust	500 hr		First service — 1st 50 hours, then every 500 hours
Battery	Test		6 mo	Every six months - check state of charge and condition with 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	Belt tensioning spring compression, side bolts	5/8	inch	between washer and bearing carrier
Clearance	Belt tensioning spring compression, stator stud nuts	1/2	inch	between washer and support slide
Gap	Ignition magneto (armature) to flywheel air gap	0.012" to 0.015"	inch
Gap	Spark plug gap	0.030	inch (0.8 mm)
Other	AC voltage regulation	115	volts	at 60 Hertz AC frequency
Other	Compression ratio	8.6 to 1
Other	Nominal starter amp draw in generator	60	Amps
Other	Normal battery charge output	0.8 to 2	Amps	no load to full load
Other	Rotor amp draw	0.85	A	±20% current draw
Other	Rotor amp draw	0.87-.79	A	±20% current draw
Other	Rotor amp draw	1.2	A	±20% current draw
Other	Starter motor maximum amps	50	Amps	bench test
Pressure	Engine oil pressure (low oil pressure switch test)	above 10	psi	engine running
Pressure	Fuel pump outlet pressure	2.0 to 3.5	psi
Pressure	LP gas pressure at LPG shut off valve inlet	11-14	inches water column
Pressure	LP gas pressure at gaseous fuel solenoid valve and secondary regulator inlet	11	inches water column	optimum
Pressure	LP gas pressure to solenoid valve	14	inches water column	do NOT exceed
Pressure	LP gas system leak test pressure	90	psi (620 kPa)	not less than, test with soap and water solution
Pressure	Low oil pressure switch trip point	below 10	psi	switch closes below this pressure
Resistance	AC power winding (11P-22P, 11S-22S, 33-44)	0.157 - 0.182	ohms	at 20°C (68°F), tolerance ±5%
Resistance	AC power winding (11P-22P, 11S-22S, 33-44)	0.209 - 0.242	ohms	at 20°C (68°F), tolerance ±5%
Resistance	AC power winding (11P-22P, 11S-22S, 33-44)	0.280 - 0.320	ohms	at 20°C (68°F), tolerance ±5%
Resistance	Battery charge resistor (R1)	1	ohm, 25 watt
Resistance	Battery charge winding (Wires 55 & 66)	0.092 - 0.107	ohms	at 20°C (68°F), tolerance ±5%
Resistance	Battery charge winding (Wires 55 & 66)	0.100 - 0.116	ohms	at 20°C (68°F), tolerance ±5%
Resistance	Battery charge winding (Wires 55 & 66)	0.104 - 0.120	ohms	at 20°C (68°F), tolerance ±5%
Resistance	Battery charge winding (Wires 55 & 77)	0.076 - 0.088	ohms	at 20°C (68°F), tolerance ±5%
Resistance	Battery charge winding (Wires 55 & 77)	0.087 - 0.101	ohms	at 20°C (68°F), tolerance ±5%
Resistance	Battery charge winding (Wires 55 & 77)	0.100 - 0.116	ohms	at 20°C (68°F), tolerance ±5%
Resistance	Bi-metal heater assembly resistance	37	ohms	±20%
Resistance	Choke solenoid coil resistance	3.7	ohms
Resistance	Excitation 'DPE' winding (Wires 2 & 6)	1.12 - 1.30	ohms	at 20°C (68°F), tolerance ±5%
Resistance	Excitation 'DPE' winding (Wires 2 & 6)	1.41 - 1.63	ohms	at 20°C (68°F), tolerance ±5%
Resistance	Excitation 'DPE' winding (Wires 2 & 6)	1.59 - 1.84	ohms	at 20°C (68°F), tolerance ±5%
Resistance	Fuel solenoid coil resistance (gasoline)	38.0	ohms
Resistance	LPG fuel solenoid coil resistance	30-32	ohms
Resistance	Rotor minimum insulation resistance	1.5	megohms
Resistance	Rotor winding (slip ring to slip ring)	10.81	ohms	at 20°C (68°F), tolerance ±5%
Resistance	Rotor winding (slip ring to slip ring)	14.50 - 16.0	ohms	at 20°C (68°F), tolerance ±5%
Resistance	Rotor winding (slip ring to slip ring)	14.88	ohms	at 20°C (68°F), tolerance ±5%
Resistance	Starter contactor relay coil resistance	155	ohms
Resistance	Stator minimum insulation resistance (120 VAC)	1.12	megohms	per formula (rated volts/1000)+1
Speed	2-pole rotor speed for 60 Hertz	3600	rpm
Speed	Engine cranking speed for spark test	350	rpm or more	cranking
Speed	Governed no-load rotor speed	3720	rpm	no electrical load
Speed	No-load AC output frequency	62-63	Hertz	no load
Speed	No-load frequency	62	Hz	governor set point, no electrical load
Speed	Starter motor minimum rpm	4500	rpm	bench test
Temperature	High temperature switch setting (LP models)	284	°F (140°C)	closes on high temp
Temperature	High temperature switch setting (gasoline models)	270	°F (132°C)	closes on high temp
Temperature	Oil temperature switch actuation (LP units)	284	°F
Temperature	Oil temperature switch actuation (gasoline units)	270	°F
Torque	Connecting rod cap bolts	16.2 - 19.8	ft-lbs
Torque	Crankcase breather mounting screws	5-8	ft-lbs
Torque	Crankcase breather screws	5-8	ft-lbs
Torque	Exhaust outlet bolts	18	ft-lbs
Torque	Fan retainer	16 - 20	ft-lbs
Torque	Flywheel nut	135 - 165	ft-lbs
Torque	Governor clamp bolt	70	inch-pounds (8 N-m)
Torque	Governor lever pinch bolt	120	in-lbs

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	5W-30 or 5W-20			Data decal (SAE VISCOSITY) alternate viscosity
Engine oil	SAE 10W-30	API classification 'For Service SF'	1.8 liters	Crankcase capacity 1.8 liters or 1.9 quarts with oil filter change; do not pour in additives
Engine oil	SAE 30 or 10W-30			Data decal (SAE VISCOSITY); temperature 40°F and higher
Engine oil	SAE 5W-30	API classification 'For Service SF'		Used to refill crankcase during out-of-service storage
Fuel	Gasoline or LP (vapor withdrawal)			Shelf life on gasoline is 30 days; a fuel stabilizer must be used at all times. LP must be supplied at 11-14 inches water column.
Fuel	High quality UNLEADED gasoline			Leaded REGULAR grade acceptable substitute; alcohol content must not exceed 10 percent ethanol; do NOT use methanol
Other	LP (liquid propane) gas			Vapor withdrawal type systems only

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

Procedures

Adjust Choke Solenoid adjustment

Loosen screws retaining choke solenoid to its bracket.
Slide choke solenoid in slotted holes to adjust axial movement of solenoid plunger.
Adjust until, with choke plate closed, solenoid is bottomed in its coil.
Tighten the two screws; verify plunger and linkage move freely.

Adjust Engine Governor adjustment

Tools: pliers

Loosen the governor clamp bolt.
Hold governor lever at wide open throttle and rotate governor shaft fully clockwise.
While holding, tighten governor clamp bolt to 70 inch-pounds (8 N-m).
Start engine and let it stabilize.
Turn adjuster nut to obtain 62 Hertz.
Check AC voltage; adjust voltage regulator if needed.

Adjust Valve Clearance adjustment

Tools: 10mm allen wrench, feeler gauge, crow's foot

Loosen the rocker arm jam nut.
Use a 10mm allen wrench to turn the pivot ball stud while checking clearance with a feeler gauge.
When clearance is correct, hold the pivot ball stud and tighten the jam nut with a crow's foot.
Recheck valve clearance to be sure it did not change.

Adjust Voltage Regulator adjustment

Set frequency at 62.5 Hertz with no load on generator.
Slowly turn the voltage adjust pot until 124 VAC is measured.
If voltage is not adjustable, refer to troubleshooting.

Check and Adjust Valve Clearance adjustment

Tools: 10mm allen wrench, feeler gauge, crow's foot torque wrench

Adjust valve clearance with engine at room temperature, piston at TDC of compression stroke.
Loosen rocker arm jam nut, use 10mm allen wrench to turn pivot ball stud while checking clearance with feeler gauge.
Set intake valve clearance 0.002-0.004 in and exhaust valve clearance 0.002-0.004 in.
Hold pivot ball stud with allen wrench and tighten rocker arm jam nut to 174 inch-pounds with a crow's foot.
Recheck valve clearance after tightening jam nut.
Install rocker arm cover with new gasket and retain with four screws.

Governor Adjustment adjustment

Tools: Pliers

Loosen governor clamp bolt.
Push spring end of governor lever clockwise to wide open throttle position.
Hold governor lever at wide open throttle and rotate governor shaft fully clockwise with pliers.
Tighten governor clamp bolt to 70 inch-pounds (8 N-m) while holding shaft and lever.
Start engine, let stabilize and warm up at no-load.
Turn adjuster nut to obtain 62 Hertz frequency reading.
Reposition governor spring in lever slot if droop is excessive or for greater stability.
Recheck frequency and readjust adjuster nut to obtain 62 Hertz at no-load.
Check AC voltage reading; adjust voltage regulator if incorrect.

Set Ignition Magneto Air Gap adjustment

Tools: thickness gauge

Rotate flywheel until magnet is under the module armature laminations.
Place a 0.012-0.015 inch thickness gauge between flywheel magnet and module laminations.
Loosen mounting screws and let magnet pull magneto down against gauge.
Tighten both mounting screws.
Remove thickness gauge by rotating flywheel.
Repeat for second magneto.

Voltage Regulator Adjustment adjustment

⚠ Adjustment must be done only when unit is running at correct governed no-load speed

Run unit at no-load with frequency set to 62.5 Hz.
Slowly turn voltage adjust pot on voltage regulator until 124 VAC is measured.
If voltage is not adjustable, proceed to troubleshooting Problem 2.

Compression Test diagnostic

Tools: compression gauge

Remove both spark plugs.
Insert a compression gauge into either cylinder.
Crank engine until there is no further increase in pressure.
Record the highest reading.
Repeat for the remaining cylinder and record.

Cylinder Leak Down Test diagnostic

Tools: cylinder leak down tester, air source

Remove a spark plug and remove the valve cover.
Rotate crankshaft until piston reaches top dead center; both valves closed.
Lock flywheel at top dead center.
Attach leak down tester adapter to spark plug hole.
Connect air source of at least 90 psi and adjust regulated pressure to 80 psi.
Read cylinder pressure; 20 percent leakage is normally acceptable.
Listen for air escaping at carburetor, exhaust and crankcase breather.
Repeat on the remaining cylinder.

Starter Motor Performance Test diagnostic

Tools: clamp-on ammeter, tachometer (P/N 042223), fully charged 12-volt battery, test bracket

A fully charged 12 volt battery is required.
Connect jumper cables and clamp-on ammeter as shown.
Activate the starter motor and note ammeter and tachometer readings after 2-4 seconds stabilization.
Good starter will be within minimum rpm and maximum amps specification.

Stator Short-to-Ground Insulation Test diagnostic

⚠ Insulation resistance testers are a source of high and dangerous electrical voltage

Tools: Hi-pot tester or megohmmeter

Disconnect and isolate all stator leads including sensing, excitation, battery charge and power leads.
Connect terminal ends of all stator leads together.
Connect tester leads across all stator leads and to frame ground on stator can, apply 1500 volts for no more than 1 second.
If breakdown indicated, clean and dry stator and re-test; replace stator if it fails second test.

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	120VAC only (single load)	Stator power leads 11P and 33; customer connections T1 (Red), T2 (White), T3 (Black)	Figure 1-8, page 7. Total load may not exceed the generator rated power output.
120	single phase	120 VAC loads only - one load with maximum total wattage equal to the generator's rated power output; 120V across the generator output terminals	T1 (red), T2 (white), T3 (black), green ground; grounded neutral	Figure 1.1/5.1 - Connection for 120 Volts Only
120 VAC only	1-Phase	Single load, 120V across output terminals	11P/22P, 33/44	Max wattage equal to rated output
120/240	1	Dual voltage output	Stator output leads 11P and 44 form the two hot leads (T1-Red and T3-Black); junction of leads 22P and 33 forms the Neutral line (T2-White), neutral remains grounded	Figure 1-9. If reconnected for dual voltage the unit is no longer RVIA listed. Units with two 30A or two 35A breakers may reuse existing breakers; units with a 30A and a 20A breaker may use two 25A main breakers with a connecting piece between handles.
120/240	single phase	120/240 VAC loads - one load with maximum total wattage equal to rated output at 240V; or two separate loads each up to half rated output at 120V	T1 (red), T3 (black) are 'hot'; T2 (white) is the grounded neutral; green lead connects to ground	Figure 1.2/5.3 - Connection for 120/240 Volts; units not listed per RVIA/ANSI when reconnected for dual voltage output
120/240 VAC	1-Phase	Dual voltage output, two hot leads T1(11P/44 red) T3(33 black), neutral T2 (22P/33 white)	11P, 22P, 33, 44	No longer RVIA listed if reconnected for dual voltage

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 displacement of the Generac 480c?

The Generac 480c has a displacement of 0.66 liters.

Which generators use the Generac 480c engine?

The Generac 480c powers 4 generator set(s), including Generac POWERPACT 55, Generac POWERPACT 66, Generac POWERPACT 70, Generac QuietPact 55.

What is a common problem with the Generac 480c engine?

A commonly reported issue on generators using the Generac 480c is: Engine cranks but will not start — spark plug is wet. Cause: Overchoking.