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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, 4.0CCK, 4.0CCK-3CR and 4CCK. 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 4.0CCK 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

Out of Fuel
Fix: Check fuel
Low or Discharged Battery
Fix: Check and replace if necessary.
Loose or Corroded Battery Connection
Cause: Faulty Starter
Lean Fuel Mixture
Fix: Readjust
VOLTAGE UNSTEADY BUT ENGINE NOT MISFIRING
Cause: Speed too low.
Fix: Adjust governor to correct speed.
VOLTAGE LOW AT FAR END OF LINE BUT NORMAL NEAR POWER PLANT
Cause: Too small line wire for load and distance.
Fix: Install larger or extra wires. Or reduce load.
The speed may remain about the same or increase when the load is applied, resulting in a frequency 1 or 2-cycles Aigker than the no load frequency.
Fix: If the rise in frequency is more than 2-cycles, lessen the internal spring tension. If there is a drop in the frequency, increase the booster internal spring tension. To increase the tension, pull out on the spring bracket, and move the pin to a different hole.
Spark plug burned or carboned.
Fix: Install new plug.
Sludge on oil cup screen.
Fix: Clean screen & air sump.
SHARP METALLIC THUD, ESPECIALLY WHEN COLD ENGINE FIRST STARTED
Cause: Low oil supply.
Fix: Add oil.
PINGING SOUND WHEN ENGINE IS SUDDENLY OR HEAVILY LOADED!
Cause: Wrong spark plug.
Fix: Install correct spark plug.
Oil too light or diluted from leaking fuel pump diaphragm.
Fix: Drain. Refill with proper oil. Repair or replace fuel pump.
Oil too heavy grade.
Fix: Drain. Refill.
Oil taa low.
Fix: Add oil.
Oil relief valve stuck.
Fix: Clean by-pass. Replace if needed.

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
Fuel filter			149-202		Amazon eBay
Oil filter			122-37		Amazon eBay 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	buy

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
Fuel supply	Check	8 hr
General	Inspect	8 hr
General inspection	Inspect	8 hr
Oil level	Check	8 hr		During break-in, check at least every 8 operational hours.
Air cleaner	Clean	50 hr		Perform more often in extremely dusty conditions; replace element every 500 hours
Battery electrolyte	Check	200 hr
Crankcase oil	Change	50 hr		First service — Drain initial oil fill after 50 hours while engine is hot; change every 50 operating hours in dusty/low temperature conditions.
Engine oil	Change	50 hr		First service — Change crankcase oil after first 50 hours of operation
Governor linkage	Clean	50 hr
Governor linkage	Lubricate	50 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
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	Replace	100 hr		if not changed within last 100 hours
Breaker points	Change	200 hr		Change every 200 hours of operation.
Breaker points	Check	200 hr		Critical maintenance schedule
Crankcase breather	Clean	200 hr
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
Carbon & lead	Clean	1000 hr
Carbon & lead	Other	1000 hr		Remove carbon & lead - critical maintenance schedule
Carburetor	Clean	1000 hr		Critical maintenance schedule
Generator	Clean	1000 hr		Critical maintenance schedule
Oil base	Clean	1000 hr		Remove & clean oil base - critical maintenance schedule
Valve clearance	Check	1000 hr		Critical maintenance schedule
Breaker arm pivot shaft	Lubricate	1200 hr		Place a drop of light oil on breaker arm pivot shaft.
General	Other	5000 hr		General overhaul - critical maintenance schedule
General overhaul	Other	5000 hr
Valves	Other	5000 hr		Grind valves - critical maintenance schedule

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	0.006-0.012	in
Clearance	Crankshaft main bearing - journal to bearing clearance	.0025 - .0038	in
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 to guide clearance	0.0025-0.004	in
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 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
Clearance	Out-of-Round	0.002	in
Clearance	Pinion to housing clearance	1/16 to 1/8	inch	pinion in operating position
Clearance	Piston Clearance in Cylinder	.0015-.0035	in.	Measured Below Oil Control Ring 90° From Pin
Clearance	Piston Pin Clearance in Connecting Rod	0.0002-0.0007	in
Clearance	Piston Pin in Piston	Thumb Push Fit
Clearance	Piston Pin in Rod	0.0001 min / 0.0006 max	inches (0.0025-0.0152 mm)	at room temperature 70°F

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
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-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.
Fuel	Clean, fresh, regular grade automotive gasoline			Do not use highly leaded premium types.
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	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
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

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.

Carburetor Main Jet and Idle Adjustment adjustment

Tools: Carburetor adjustment wrench

Make all adjustments with the engine at normal operating temperature.
For main jet, connect a full or nearly full load; turn main adjusting needle out about two full turns.
Turn needle in slowly until engine begins to lose power and speed, then out slowly until engine runs smoothly at full power and speed.
If hunting occurs, open main adjusting needle a little more (no more than 1/2 turn beyond maximum power).
For idle jet, with no load, turn needle in until engine loses considerable speed, then out until engine runs smoothly.

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, 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	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	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.
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
250VDC		12V start		Wiring diagram 611B276
250VDC		6V start		Wiring diagrams 602B164, 611B244
250VDC		Manual start		Wiring diagram 602A174
277/480	3	Voltage Code 9X		277/480V, 3PH

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 6 generator set(s), including Cummins/Onan 3.5CCK, Cummins/Onan 4.0CCK, Cummins/Onan 4.0CCK-3CR, Cummins/Onan 4CCK, Cummins/Onan 5.0 CCK.

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: Out of Fuel. Fix: Check fuel.