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Cummins/Onan CCK Engine

The Cummins/Onan CCK is a 0.5 L 2-cylinder natural engine rated at 1800 rpm. It powers generator sets from Cummins/Onan, including the 3.5CCK, 4.0 CCK-3R, 4.0CCK and 4.0CCK-3CR. It holds 2.8 L (0.7 gal) of oil.

Also known as: Onan CCK

0.498 L

Displacement

Cylinders

1800 rpm

Rated speed

2.8 L

Oil capacity

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

Engine specifications

Oil capacity	2.8 L
Displacement	0.498 L
Cylinders	2
Aspiration	natural
Rated speed	1800 rpm

Generator sets powered by this engine

Cummins/Onan 3.5CCK Cummins/Onan 4.0 CCK-3R Cummins/Onan 4.0CCK Cummins/Onan 4.0CCK-3CR Cummins/Onan 4CCK Cummins/Onan 5.0 CCK Cummins/Onan 5CCK

How to read your Cummins/Onan engine serial & model number →

Common problems

Voltage drops under heavy load
Cause: Engine lacks power
Fix: See remedies for engine misfires under heavy load.
Hot crank
Cause: Lack of fuel or faulty carburetion
Fix: Refill tank. Check fuel system. Clean, adjust, as necessary.
Low oil pressure
Cause: Defective gage
Fix: Replace.
Excessive oil consumption, light blue smoky exhaust
Cause: Oil leaks from oil base or connections. This does not cause smoky exhaust.
Fix: Replace gaskets. Tighten screws and connection. Check breather valve.
Pinging sound when engine is suddenly or heavily loaded
Cause: Wrong spark plug
Fix: Install correct spark plug.
High oil pressure
Cause: Defective gage
Fix: Replace.
Engine will not start when cranked
Cause: Battery discharged
Fix: Refill tank. Check fuel system. Clean, adjust, as necessary.
Engine overheating
Cause: Insufficient cooling air
Fix: Check air entrance and exit.
Engine misfires at light load
Cause: Spark plug gap too narrow
Fix: Adjust to correct gap
Engine misfires at heavy load
Cause: Spark plug gap too wide
Fix: Adjust gap
Black, smoky exhaust, excessive fuel consumption, fouling of spark plug with soot, possible lack of power under heavy load
Cause: Fuel mixture too rich
Fix: Adjust carburetor or choke. Install needed carburetor parts.
Out of Fuel
Fix: Check fuel
Loose or Corroded Battery Connection
Cause: Faulty Starter
Fails to crank
Cause: Bad battery connection
Fix: Clean and tighten all battery and cable connections.
Cranks but won't start F2
Cause: Blown fuse (F2)
Fix: Replace fuse (F2) on control.

Compiled from service & troubleshooting documentation across every generator set that uses the Cummins/Onan CCK.

Maintenance schedule

Item	Spec	Capacity	Part #	Interval
Air filter			140B495	500 hr	Amazon eBay $22.91
Fuel filter			149-202		Amazon eBay
Oil filter			122-37		Amazon eBay $16.95 NAPA $17.50
Battery			—
Belt	Belt, Alternator		511-76		Amazon eBay
Coolant			—
Fuel	Fuel system and pump		—
Oil	API SE or SE/CC	4.0 liters	—	100 hr
Spark plug	0.025' GASOLINE		167-242	100 hr	eBay

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

Repair guides

Step-by-step procedures compiled from the Cummins/Onan service manual for this engine.

Service intervals

Item	Action	Hours	Months	Notes
Air cleaner oil level	Check	8 hr		Daily service; add oil same SAE number as crankcase.
Crankcase oil level	Check	8 hr		Daily service; add oil as necessary to full mark.
Fuel supply	Check	8 hr		Daily service; perform each 8 hours if operated more than 8 hours daily.
General	Inspect	8 hr
General inspection	Inspect	8 hr
Oil level	Check	8 hr		During break-in, check at least every 8 operational hours.
Plant cleanliness	Clean	8 hr		Daily service; wipe off dirt and spilled oil.
Air cleaner	Clean	100 hr		Perform more often in extremely dusty conditions; replace element every 500 hours
Battery electrolyte	Check	200 hr
Engine oil	Change	50 hr		First service — Change crankcase oil after first 50 hours of operation
Governor linkage	Clean	50 hr
Governor linkage	Lubricate	100 hr		Clean joints and lubricate every 50 hours
Oil	Change	50 hr		Change crankcase oil after first 50 hours; every 50 hours or sooner in dusty conditions
Spark arrester/muffler, screen type	Clean	50 hr		Remove and scrape clean or replace screen; may be blown clean with compressed air. Every 50 operating hours.
Spark arrester/muffler, spin-out type	Clean	50 hr		Remove pipe plug in bottom of muffler and run set for 5 minutes; replace plug. Every 50 hours of set operation.
Spark arresters	Clean	50 hr		Spark arresters should be cleaned every 50 to 100 hours; routine cleaning during servicing is good safety practice.
Battery	Inspect	100 hr		Keep connections tight and clean; check electrolyte.
Crankcase oil	Change	100 hr		First service — Normal conditions; every 50 hours if using diluted oil, highly leaded gasoline, or severely dusty conditions.
Dolly wheel bearings	Lubricate	100 hr		Use approved wheel bearing lubricant through Zerk fittings.
Fuel filter	Clean	100 hr		Every 100 hours or sooner, drain fuel pump and check filter element
Reduction gear box	Drain	100 hr	6 mo	First service — every six months thereafter or every 100 hours
Reduction gear box oil	Change	100 hr	6 mo	every six months thereafter or every 100 hours
Reduction gear box oil	Drain	100 hr		First service — after first 100 hours
Reduction gear drive oil	Drain	100 hr	6 mo	First service — Drain after first 100 hours, then every six months or every 100 hours, whichever is first.
Spark plugs	Check	100 hr
Spark plugs	Clean	100 hr		Clean and reset gap; replace defective plug.
Spark plugs	Replace	100 hr		if not changed within last 100 hours
Breaker points	Adjust	200 hr		Inspect, dress or replace; adjust gap to 0.020 inch at full separation.
Breaker points	Change	200 hr		Change every 200 hours of operation.
Breaker points	Check	200 hr		Critical maintenance schedule
Crankcase breather	Clean	200 hr
Exhaust system	Inspect	200 hr		Monthly service; inspect all connections.
Fuel system/filter	Clean	200 hr		Monthly service; drain tank, clean filter screen, empty fuel filter bowl.
Generator brushes/commutator	Inspect	200 hr		Monthly service; replace brushes worn to 5/8 inch or less.
Oil filter	Replace	200 hr		normally
Air cleaner cartridge	Replace	500 hr		Contractor model; install new cartridge every 500 hours.
Air cleaner element	Replace	500 hr		Begin Spec R
Brushes	Check	500 hr		Critical maintenance schedule
Commutator & collector rings	Clean	500 hr		Critical maintenance schedule
Stainless steel spark arrester screen	Replace	500 hr		For units using specially designed stainless steel screens.

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	Armature End Play	0.004-0.020	in
Clearance	Armature end play	.004 to .020	inch (0.102 to 0.508 mm)
Clearance	Camshaft Bearing	0.0015 min / 0.0030 max	inches (0.04-0.08 mm)	at room temperature 70°F
Clearance	Camshaft Bearing to Camshaft Clearance	.0015-.0030	in.
Clearance	Camshaft End Play	.003	in.
Clearance	Camshaft End Play	0.003 min	inches (0.08 mm)	at room temperature 70°F
Clearance	Camshaft bearing	0.003	in
Clearance	Camshaft bearing clearance	0.0015-0.0030	in
Clearance	Camshaft bearing journal diameter	1.3740-1.3745	in
Clearance	Camshaft bearing to camshaft clearance	.0015 - .0030	in
Clearance	Camshaft end play	0.0020-0.0033	in	at 70 F
Clearance	Camshaft end play	0.0030-0.0120	in
Clearance	Carburetor float clearance (between float bowl gasket and float)	.312	inches (7.938 mm)
Clearance	Commutator Runout Maximum	0.004	in
Clearance	Connecting Rod End Play	.002-.016	in.
Clearance	Connecting Rod End Play (Ductile Iron)	0.002 min / 0.016 max	inches (0.05-0.41 mm)	at room temperature 70°F
Clearance	Connecting rod end play	.002 - .016	in
Clearance	Connecting rod end play (aluminum rod)	0.002-0.016	in
Clearance	Connecting rod end play (forged rod)	0.002-0.003	in
Clearance	Connecting rod journal diameter	1.6252-1.6260	in
Clearance	Connecting rod side clearance	0.0020-0.0160	in
Clearance	Crankshaft End Play	.006-.012	in.
Clearance	Crankshaft End Play	0.0020-0.012	in
Clearance	Crankshaft End Play	0.006 min / 0.012 max	inches (0.15-0.30 mm)	at room temperature 70°F
Clearance	Crankshaft Main Bearing	0.0024 min / 0.0042 max	inches (0.061-0.10 mm)	at room temperature 70°F
Clearance	Crankshaft Main Bearing - Journal to Bearing Clearance	.0025-.0038	in.
Clearance	Crankshaft Main Bearing Journal - Standard Size	1.9992 min / 2.000 max	inches (50.779-50.8 mm)
Clearance	Crankshaft Rod Bearing Journal - Standard Size	1.6252 min / 1.6260 max	inches (41.280-41.300 mm)
Clearance	Crankshaft Rod Journal to Rod Bearing Clearance	.0020-.0033	in.
Clearance	Crankshaft end play	.006 - .012	in
Clearance	Crankshaft end play	0.0015-0.003	in	at 70 F
Clearance	Crankshaft end play	0.0025 to 0.0035	inch
Clearance	Crankshaft end play	0.006-0.012	in
Clearance	Crankshaft main bearing - journal to bearing clearance	.0025 - .0038	in
Clearance	Crankshaft main bearing clearance, aluminum alloy flanged prior Spec F	0.002 to 0.003	inch
Clearance	Crankshaft rod journal to rod bearing clearance	.0020 - .0033	in
Clearance	Cylinder Bore - Standard Size	3.2490 min / 3.2500 max	inches (82.525-82.550 mm)
Clearance	Cylinder Bore Honed Diameter	3.2490-3.2500	in
Clearance	Cylinder bore - honed	3.249 - 3.250	in
Clearance	Exhaust Valve Stem Diameter	0.3410-0.3415	in
Clearance	Exhaust valve stem clearance in guide	0.0025 to 0.004	inch
Clearance	Exhaust valve stem to guide clearance	0.0025-0.004	in
Clearance	Front gear cover oil seal installation depth	1-1/32	in	rear spring side of casing from gear cover mounting face
Clearance	Fuel injection pump installation dimension	3.260	in	new camshaft; instead of 3.254
Clearance	Gear lash at oil pump	approximately .005	in
Clearance	Governor cup in-and-out travel	7/32	in	cup held against flyballs
Clearance	Intake Valve Stem Diameter	0.3425-0.3430	in
Clearance	Intake valve stem clearance in guide	0.001 to 0.0025	inch
Clearance	Intake valve stem to guide clearance	0.0010-0.0025	in
Clearance	Main bearing clearance	0.0025-0.0038	in
Clearance	Main bearing inside diameter CCK (installed)	2.0020-2.0030	in
Clearance	Main bearing inside diameter CCKA/CCKB (installed)	2.0015-2.0040	in
Clearance	Main bearing journal diameter	1.9992-2.0000	in
Clearance	Maximum Allowable Taper	0.005	in
Clearance	Oil Pump Gear Backlash	.002-.005	in.
Clearance	Oil Pump Gear Backlash	0.002 min / 0.005 max	inches (0.05-0.13 mm)	at room temperature 70°F
Clearance	Oil by-pass valve plunger diameter	.3365 to .3380	inches (8.55 to 8.59 mm)
Clearance	Oil by-pass valve spring free length	2-5/16	inches (58.74 mm)
Clearance	Oil pump gear backlash	.002 - .005	in
Clearance	Oil pump gear backlash	0.0005-0.0015	in

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
Coolant	Ethylene glycol base anti-freeze mixed with water				Do NOT use straight 100% ethylene glycol. Normal mixture approximately 50% anti-freeze and 50% water; ratio varies with ambient temperature.
Coolant	coolant under pressure				Do not open radiator pressure cap when coolant temperature is above 212°F (100°C) or while engine is running.
Engine oil		API designation SE or SE/CC			Use oil with API designation SE or SE/CC. Do not use an oil with designation CD unless it is also designated SE and the oil manufacturer certifies it will perform satisfactorily in gasoline engines. For gaseous operation, use an ashless or low-ash detergent oil specifically made for gaseous-fueled engines.
Engine oil	API SE or SE/CC	API SE or SE/CC			For gaseous operation, use ashless or low-ash detergent oil specifically made for gaseous-fueled engines. Do not use CD unless also designated SE.
Engine oil	Ashless or low-ash detergent oil				For gaseous operation
Engine oil	SAE 10W	API MS or MS/DG		4.0 U.S. quarts	0°F to 30°F
Engine oil	SAE 30	API MS or MS/DG		4.0 U.S. quarts	Above 30°F
Engine oil	SAE 30 above 30°F; SAE 10W or 5W-20 from 0°F to 30°F; SAE 5W-20 below 0°F	SE or SE/CC; MS or MS/DG; MIL-L-2104B		4.0 U.S. quarts	Do not mix brands or grades.
Engine oil	SAE 5W (5W-20 if 5W not available)	Service MS or MS/DG		4.0 U.S. quarts	Below 0 F; do not mix brands or grades; oil consumption usually higher with multi-viscosity all-weather oil
Engine oil	SAE 5W or SAE 10W plus 10% kerosene	API Service DG or MS/DG detergent oil	below -18°C	4.0 U.S. Quart	Below 0°F (-18°C). Use 40 ounces kerosene to each quart of oil if SAE 5W not available; mix thoroughly before pouring.
Engine oil	SAE 5W-20	API MS or MS/DG		4.0 U.S. quarts	Below 0°F
Engine oil	SE or SE/CC	API SE or SE/CC (MS sequence / ASTM G-IV; MIL-L-2104B)		4.0 U.S. quarts	Above 30 F use SAE 30; 0 F to 30 F use SAE 10W or 5W-20; below 0 F use SAE 5W-20. Do not mix brands or grades.
Engine oil	SAE 50	API Service DG or MS/DG detergent oil	above 32°C	4.0 U.S. Quart	Above 90°F (32°C). Capacity 4 U.S. Quart typical; dimensional table lists 3 Quart for 305CCK.
Fuel	ASTM 2-D or 1-D diesel fuel	Cetane number 45			Use Number 1-D diesel fuel when ambient temperatures are below 32 F (0 C) or during long periods of light load/cyclic operation.
Fuel	Clean, fresh, regular grade automotive gasoline				Do not use highly leaded premium types.
Fuel	Regular automotive type gasoline, at least 68 octane			4.0 U.S. Gallon	Portable type plant has 4 gallon rectangular tank mounted over generator. Do not use highly leaded premium gasoline.
Fuel	Regular grade automobile gasoline				Do not use highly leaded premium types; never fill tank while engine is running; leave space for fuel expansion
Fuel	clean, fresh, regular grade, automotive gasoline				Do not use highly leaded premium types.
Fuel	regular grade automotive gasoline				Do not use highly leaded premium types.
Fuel	unleaded or regular grade gasoline				Use clean, fresh, unleaded or regular grade gasoline. Do not use highly leaded premium fuels. Use regular gasoline for the first 25 hours, then use unleaded gasoline thereafter.
Gear oil	SAE 50 motor oil or SAE 90 mineral gear oil			1.0 pint	Gear box holds 1/2 pint U.S. measure (.24 litre). Do not use extreme pressure or hypoid lubricants.
Grease	Approved wheel bearing lubricant				Dolly wheel bearings through Zerk fittings.
Grease	Fibrous grease or stiff cup grease				Fill space between oil seal lips; use cup grease to hold bearing thrust washers and to lubricate sheave hub bearing and spring pawls
Grease	Powdered graphite or light non-gummy oil				Governor arm ball joint.
Other	LPG				Gaseous fuel optional. LPG vaporizer regulator reduces LPG tank pressure to a uniform outlet pressure of 7 psi (48.3 kPa).
Other	propane				LPG is heavier than air and settles in low places.

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 Breaker Points adjustment

Tools: flat thickness gauge

Remove cover screws
Remove spark plugs
Turn flywheel clockwise about 1/4 turn after top center
Loosen screws A and turn cam B until gap is .020 in.
Retighten screws and recheck gap
Replace spark plugs and cover

Adjust Carburetor Idle Jet adjustment

Tools: idle adjustment tool

Run engine at no load
Turn idle needle in until engine slows considerably
Turn out until engine runs smoothly

Adjust Carburetor Main Jet adjustment

Tools: main adjustment wrench

Connect full load
Turn main needle out about two turns
Turn in slowly until engine loses power
Turn out slowly until smooth at full power
Do not open more than 1/2 turn beyond maximum power

Adjust Electric Choke adjustment

Loosen two cover retaining screws
Turn cover clockwise for less choking action
Turn counterclockwise for more choking action
Retighten cover screws

Adjust Sisson Choke adjustment

Tools: 1/16 in. diameter rod

Insert 1/16 in. rod through shaft hole into mounting flange notch
Loosen choke lever clamp screw
Adjust choke lever so plate is closed or not more than 5/16 in. open
Tighten screw and remove rod

Adjust anti-dieseling solenoid adjustment

With set stopped, turn lever counterclockwise; set screw so plates are closed but not binding.
Check lever has approximately 30 degrees travel counterclockwise from vertical.
Start set; lever should rotate approximately 60 degrees clockwise from stopped position.
Check solenoid plunger is fully seated.
If not, adjust distance between plunger and lever arm; repeat steps.

Adjusting the Gas Pressure Regulator adjustment

Tools: Manometer reading up to 14 inches water column

Use a manometer which reads up to 14 inches (355.6 mm) water column.
Shut off gas supply. Temporarily remove the 1/8-inch pipe plug at regulator inlet for testing pressure.
Connect manometer to read gas supply line pressure.
Open gas supply line valve. Alternately cover and uncover the regulator outlet with your palm. Watch manometer. If regulator closes completely, manometer holds steady reading.
If manometer reading drops slightly each time you remove your hand, regulator is leaking. Turn adjusting screw inward just enough so reading remains constant.
Close gas supply line valve. Remove manometer. Bleed air from gas supply line. Install test-hole plug in regulator. Open gas supply line valve.
See that vent fitting is installed in the regulator hole.
Secure hose between regulator outlet nipple and carburetor inlet with clamps on each end.
Operate engine to assure quick starting results.

Breaker Point Gap Adjustment adjustment

Tools: thickness gage

Crank engine to fully open breaker points (1/4 turn after top center).
Loosen and move stationary contact to correct gap.
Set breaker point gap at 0.020 in.
Secure points and check for correct gap.

Breaker Points Adjustment adjustment

Tools: Flat thickness gauge, File or fine stone

Remove the two screws and the cover on the breaker box.
Remove the two spark plugs so engine can be easily rotated by hand.
Turn flywheel clockwise approximately 1/4 turn after top center (TC).
Loosen screws (A) and turn cam (B) until point gap measures .020 in with a flat thickness gauge.
Retighten screws (A) and recheck gap.
If points are slightly burned, dress smooth with a file or fine stone; if burned and pitted, replace with a new set.
Replace spark plugs and breaker box cover.

Carburetor Adjustment adjustment

Tools: Onan carburetor wrench 420B169

Turn main adjusting needle out about two full turns.
Turn main needle slowly in until engine begins to lose power and speed.
Then turn out very slowly until engine runs smoothly at full power.
Adjust idle jet needle with engine at normal temperature and no load.
Turn idle needle in until engine loses considerable speed.
Turn idle needle out until engine runs smoothly.
Adjust float level by bending float near shaft.

Carburetor Adjustment (Gasoline) adjustment

⚠ Forcing mixture screws tight damages needle and seat.

Tools: screwdriver

Warm engine until choke fully open.
With no load, turn idle adjustment out until speed drops slightly.
Turn idle needle in until speed returns to normal.
Apply full load.
Turn main adjustment in until speed drops slightly.
Turn main needle out until speed returns to normal.

Carburetor Adjustment - Gasoline adjustment

Start engine and warm up until choke is fully open.
No load: turn idle adjustment out until speed drops slightly below normal.
Turn needle in until speed returns to normal.
Apply full load.
Turn main adjustment in until speed drops slightly below normal.
Turn needle out until speed returns to normal.

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
	1 or 3P, 2 or 3W	Manual start, Magnet service		Wiring diagrams 602B143, 602A166
115VDC		Portable		Wiring diagram 602B165
120	1	2-wire	M1, M3 (join); M2, M4 (join)	Ungrounded load wire black; grounded load wire white
120	1	Two-wire AC remote/manual	M1 (ungrounded black), M2 (grounded white)	Connect grounded white load wire to M2 and ungrounded black load wire to M1.
120, 240 or 120-240V	1P	Revolving armature reconnectible (CCK-3CR)		Reconnection of generator leads
120/208	3	4-wire	M1, M2, M3, M4	3-phase.
120/208	3	Four-wire AC remote	M1, M2, M3, M0	Single-phase lower voltage from any M1/M2/M3 to M0; three-phase higher voltage M1/M2/M3; M0 is ground load terminal.
120/208	3	Voltage Code 4		120/208V, 3PH
120/208V	3P, 4W			Wiring diagram 611C206
120/208V	3P, 4W	Portable		Wiring diagram 602B160
120/240	1	3-wire	M1; M2, M3 (join); M4	Only half nameplate rating can be taken off each 120 V connection
120/240	1	Reconnectable for 120 V, 2-wire; 240 V, 2-wire; or 120/240 V, 3-wire		Applies to sets marked ** in the Generator Set Data Table.
120/240	1	Three-wire AC remote	M1, M2, M3	Two 120 volt circuits across M1-M2 and M2-M3; one 240 volt circuit across M1-M3; M2 not used with 240 volt circuit.
120/240	1	Voltage Code 3C		120/240V, 1PH
120/240	3	Voltage Code 5O		120/240V, 3PH
120/240V	1P, 3W	Portable		Wiring diagram 602B146
120/240V	1P, 3W	Remote start		Wiring diagram 611C164
120/240V	1P, 4W	Reconnectible		Wiring diagram 611C236
120/240VAC, 32VDC				Wiring diagram 611C235
120V	1P, 2W	Manual start		Wiring diagram 611C176
120V	1P, 2W	Portable		Wiring diagram 602B144
120VAC, 32VDC				Wiring diagram 611C234
220/380	3	Voltage Code 7		220/380V, 3PH
240	1	2-wire	M1, M4 (join); M2	Ungrounded load wire black; grounded load wire white
240	3	3-wire	M1, M2, M3	3-phase.
240	3	Three-wire AC remote	M1, M2, M3	Connect one load wire to each terminal; reverse connections at any two generator terminals if 3-phase motor rotation is wrong.
240V	1P, 2W	Manual start		Wiring diagram 611C176
240V	1P, 2W	Portable		Wiring diagram 602B145
240V	3P, 3W			Wiring diagram 611C178
240V	3P, 3W	Portable		Wiring diagram 602B147

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 Cummins/Onan CCK?

The Cummins/Onan CCK engine has an oil capacity of 2.8 liters.

What is the displacement of the Cummins/Onan CCK?

The Cummins/Onan CCK has a displacement of 0.498 liters with 2 cylinders.

Which generators use the Cummins/Onan CCK engine?

The Cummins/Onan CCK powers 7 generator set(s), including Cummins/Onan 3.5CCK, Cummins/Onan 4.0 CCK-3R, Cummins/Onan 4.0CCK, Cummins/Onan 4.0CCK-3CR, Cummins/Onan 4CCK.

How often should you change the oil in the Cummins/Onan CCK?

The Cummins/Onan CCK oil change interval is every 100 hours.

What is a common problem with the Cummins/Onan CCK engine?

A commonly reported issue on generators using the Cummins/Onan CCK is: Voltage drops under heavy load. Cause: Engine lacks power. Fix: See remedies for engine misfires under heavy load..