The ONAN CCK Generator.

I think it was Bill Perkins that told me the old CCK Onan was tough. Being a flat head twin, the fuel economy isn’t that good, but many of these units were made in gasoline and propane conversions, and they have given their owners years of reliable service. The manual for a lot of the Onans can be found on Smokstack, and I hear that’s where you can find people that know these old sets inside and out. Bill Perkins says the treasure is the CCK with simple electrics, there was also one with a control board that failed in the early days.. maybe the replacements were better? This one is just the way I like it.. simple as a brick.. Kiss Engineering is at the heart of this beast.

Mine came out of a motor home, electric start, a fuel pump, very little use, and runs like a watch. I recently looked at the brush springs and found one I didn’t like the looks of.  I called my local Cummins NW Dealer in Renton Washington and got hold of Mark Magner on the parts line.

I sent him a picture of the spring, we swapped a few emails, and he sent me a drawing and part number to confirm he had found the right thing. It’ll be here in a week or so, and no shipping cost..

I was impressed with the price quote, I ordered four of them, and once I had a good part number, I found another vendor on ebay selling for near double the price.  This old Onan purrs, and it’s nice to see a company carry parts for somethign they sold over 40 years ago!

Thanks Mark… Thanks Onan



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41 Responses to The ONAN CCK Generator.

  1. John says:

    Glad you like your Onan generator! As a generator tech for them, Cummins/Onan currently keeps me fed housed, etc. 🙂

    If your unit pre-dates roughly 1987 (check the serial numbers 2nd & 3rd digit) it’s just an “Onan” (sans Cummins!).

    If you need more info on it LMK, since I have access to pretty much all of it.

    • alan says:

      we had a lightning strike at camp
      fuse blown on cck replaced
      will start now but not run
      i think relay must have been taken out(this happened once before)
      where can i find a replacement?
      can the reply be bypassed?


      • George B. says:

        You say it will start now, but not run? Do you mean that as long as you have your finger on the start toggle switch it runs?

        Take off the cover on the control box, watch the relay that comes up when you operate the start switch..if any.. there are several different CCK MODELS,you need find the right drawing, and it’s likely on line. Hold down the relay that falls off, and see if it continues to run, then investigate what is susposed to hold it up, open relay winding? There’s a Cummings Dealer (they bought Onan) in Renton WA who was very helpful in getting me new brushes for my CCK.. might be a place to start for the relay, depending on the winding and contacts, there may be quite a few suitable replacements if you can’t find the original..

        If lightening did damage when the generator was off line, might be worth looking into the reason it got int the quipment, and looking into a protections scheme. you could certainly add to thsi post by reporting back your findings..

        A reminder to all of us.. make up a book of all the drawings and info you might need during an outage.. keep them near your generator.. alan.. I’m not expert on the CCK..

    • John Wells says:

      Have overhauled a 5CCK-3CR -vintage 1983. Wiring from fields and controls has been slightly messed with. Is there any more complete wiring diagrams with wire numbers, etc on them? I have the standard diagram with the manual, but it is not detailed sufficiently. any help would be most appreciated.

      • George B. says:

        I can only say.. my local Cummins-Onan Dealer in Renton Washington went well beyond my expectations in getting me parts and drawings for my old machine.. try yours.. yes, we have readers here that might know where the mother load is AS PER on line drawings as well.


  2. Harold Madison says:

    Hey George

    I enjoyed your article on the Onan CCK generator. Starting in the early sixties for about 15 years I made a living in the Air Force maintaining 40 or so, of these generators among a host of other assorted ground support equipment. They powered portable light carts (Air Force NF-2) which also supplied 115 VAC for aircraft maintenance test equipment. These things literally ran thousands of hours a year and I can remember tearing down only one engine for internal problems. It was a near perfect example of a balanced engine, and though it never idled in normal use it could idle about as smooth as a Swiss watch.

    Scheduled maintenance was just about limited to changing oil and filters, changing spark plugs and scraping carbon out of the heads once a year. About the only unscheduled maintenance involved the 24 volt cranking battery that often times was castaways from the aircraft battery shop. Mechanics that complained about frequency control likely did not understand how to adjust the governor vacuum boost or did not replace dried out seals and diaphragm. Bad Onan mechanics were not hard to find because, like the Maytag repairman, they didn’t get much practice.

    Electrically, everything was done by relay logic. A few years ago I got a motor home CCK unit in my shop with a small circuit board on it that had failed. It had two large transistors and half a dozen diodes, caps and resistors. It had replaced a couple of relays. The local parts distributor only wanted $360 for a replacement board. He told me they had so much trouble with the solid state stuff that after a couple of years they went back to relays. How’s that for KISS? I ended up repairing the board.

    These gensets gave way to some kind of diesel unit in the 70’s I recon like all the other “mo-gas” powered Air Force ground support equipment.

    A good picture of the NF-2 can be found at:

    I enjoy your website. Keep up the good work.

    Best regards

    Harold Madison

    • George B. says:

      Thanks for your contribution here, there’s no reason that circuit board had to be so much trouble, it sounds like somone only did half the design.

    • Fred David says:

      Your post stating experiences with cck engines piqued my curiosity I have 3 of
      them one of which is a cckb powering a Bendix 400hz 120/208 model 28e01 type 1 generator I have tried all over to get a dwg showing field input requirements Did you over the years ever work on one of these units?
      I believe they saw usage in airports and on helicopters doing geological surveys
      wherever 400hz power was needed on a sitting aircraft thats if Iam correct
      any insite you can give me would be appreciated thanx Fred

    • Fred David says:

      Hi Harold during your air force days any experience with Bendix 28e01 generators 400hz 7.5kw

      • Harold says:

        Sorry, I have no experience with the cckb Bendix 400 Hz units.

        For 400 Hz equipment the USAF in my day, had Beach Aircraft MD-3s powered by a 6-cylinder Continental air cooled aircraft type engine and Wolverine Diesel M32A-60s powered by Air Research turbines. The Continental has since been replaced with a diesel engine about which I have NO knowledge. I don’t know the status of the -60. It gave considerable trouble with oil transfer tube seals and the hot end of the turbine. About 900 hours was its max life expectancy in the late 60s. It was great when it came to frequency control (400 cps + or -1, every time) but it was a thirsty beast. It could blow through 90 gallons of JP-4 in less than 8 hours, and this, running half, or less, of its 175 KVA 400 Hz capacity and none of its 500Amp, 28 Volt DC capacity. By now they may have a better mouse trap.

        There’s a lot I have forgotten about Air Force power generating equipment. You might have better luck asking John (above). The last time I saw one of the NF-2 light carts with and Onan CCK was in Alaska in 1974. I did some motor home generator work since retirement but sadly have not kept up with the newer stuff.

        There is a wealth of information available on line. One example which I have is:

        ARMY GENERATORS Technical Manuals (CD) $17.00, about 165 Lubrication Orders and Technical Manuals.

        You need to know the TO / TM number to find these. Example: ARMY TM 9-6115-641-24 Maintenance Manual, GENERATOR SET, SKID MOUNTED, MEP 802A, 5 KW, 60 Hz (Approved for public release, distribution unlimited). You’re paying for the media, not for the data.
        I have not been able to cross reference Manufactures or model numbers to military technical manual numbers. Maybe you will have better luck.

        This particular TM is 296 pages of PDF, about 3 megabytes.

        • Fred David says:

          Hi Harold thnx for reply and info I will keep looking I have been doing reverese engineering on this unit as follows. These units have no residual magnetism so I have used my variac and a bridge rectifier and it seems 90v dc is what it likes polarity doesnt seem to matter unit puts out power and will work on any resistive load
          or most universal motors Units motor gen are very high
          quality truly a travesty to junk them. Anyway the above

          may help someone else cheers

  3. George B. says:

    Thanks for the comments and offer.. I like simplicity, this old Onan is fairly quiet and simple..

  4. Thomas Z says:

    Thanks for the ONAN Article. I also believe in “KISS” systems, I just purchased a used 4.0CCK ONAN/GEN 120/240 V. and plan to use it for the house for basic power needs when the grid goes offline.
    Best Regards,

    • George B. says:

      And… can you believe my Cummins experience! The parts man put a lot of work into finding the right brush springs for my rig.. A 40 year old machine! How many other companies would have told us to get lost after 10-12 years? I spent the better part of the day building a custom frame out of one inch square tube for this set. I don’t need another generator, but I might keep this one around a while longer. The stock electric fuel pump makes it possible to shove a hose into a five gallon or larger fuel can.. put your finger on top of the fuel pump relay and the set seems to have no problem priming the hose for a very quick start. One can easily install a remote prime button, and of course a remote run and stop button was a normal part of many onan installs.

      • John says:

        And don’t forget about that ‘sneaky’ hidden fuel filter inside the fuel pump. I’ve seen people get caught on that one a few times, wondering why the pump sounds like it’s running, but nothing goes through it.

      • ThomasZ says:

        I wish more companies would be like this in North America. I purchase a Reliance Manual Transfer switch (20216A) for power outages and will hook it up this weekend. This unit will be used for when the power go out. Thanks for your Kiss principal knowledge.
        Have a Great Easter Weekend to you and yours.
        Best Regards,

    • larry burke says:

      I have recently bought an old cck model (1972, if I’m reading the serial # correctly) which I assume came from an RV.
      For years I have heard about ONAN, in general, and have heard nothing but positive comments. Finally had this opportunity to get one for cheap, which runs well.
      This unit is in use daily, as it is my only source of energy, for now.
      I am a mechanic (retired) by trade but have no experience with ONAN, and even more technically challenged when it comes to electrical theory relating to generator systems.
      Seeing that you have apparently the same or similar unit, I was hoping I could pick your brain from time to time, if for nothing else, resources.
      This site itself seems like a great place for info, but not being well versed with ONAN I don’t really know if there are major differences between models or not, but assume so at least to the extent of practical application.
      That being said, I had hoped that since your ONAN is similar that you could perhaps guide me as I go.
      There are a few peculiarities of this unit that I’m not familiar with, compared to other generators and engines, that I have questions about.
      Regardless, any help of any kind would be welcome.
      Larry J Burke

  5. Homealone777 says:

    Well; I’m glad to hear about someone else having one of these Onan Gensets. The Lord blessed me with one about 20yrs ago. It came out of a motor home and has remote start. It’s a 1976, 16 HP, twin; And it has the solid state board. When I got it ,it would run just fine and would power my worklite, but not much else. When I took the cover off the electronics board, I could see it was burned. At the time I was building a house so all my money was tied up in that, so I put it up in my shed to keep it dry. Time passed and I forgot about it until recently. I found a Cummins place where I live, and have found a supposedly better made board, but I have’nt had time to go get it. I guess I might ought to do it before times change and I can’t. I’ve heard a lot of good reports on them. Lord Willing, until I get that Lister setup I want so bad; I’ll use this for now. Thanks for all the input on that George B. Coming from you, that means a lot. Much appreciated.

  6. bob g says:

    i have a couple of the cck onan’s, fine engines in my opinion

    i am also a huge fan of the kohler k-series engine’s, and as far as i am concerned they are about as good a flat head engine as was ever made.

    my best buy a couple years ago was a 4kw motorhome generator
    kohler 1800rpm genset, brand new, never started since the factory, complete with all the factory stuff, manuals and other paperwork.
    it is a 1973 model and as far as i am concerned i wouldn’t part with it for 10x what i paid for it, (i paid 600bucks so that should tell you what i think of this jewel)

    second best buy was a miller AEAD 200le AC/DC welder, 100% duty cycle at 225amps AC and 200amps DC, onan powered. bought it because it would not weld but ran flawlessly for 200 bucks. took
    15 minutes to fix a loose female spade and it is back to life again.
    i would buy them all day long at this price!

    only other flathead engine i like better than either the kohler or onan has to be the continental F series. in my opinion if the world came to an end the F series would be my first choice hands down for a “mad max” survival vehicle engine. put an allison mt40/41 automatic and you would have an indestructible power unit, if not the fastest.

    in my opinion every diy’er that is either producing or thinking of producing his own power should have either an onan or kohler flathead engine in the wings. they are incredibly good buys if you watch for them and seem to run for decades with very little repair/overhaul cost.

    bob g

  7. George B. says:

    Bob… if they would have only made a diesel….. 🙁

    • Harold says:


      I have a bad feeling that I missed out on a good deal back in early July this year. I answered the following add in a local sale paper:

      ALLMOND TRAILER MOUNTED GENERATOR and light plant. The light mask can be raised up 10-12 feet. Has a Laister diesel engine, very economical, $850. Call 270-749-xxxx.

      The engine would probably run a long time on its 50 gallon fuel tank. It was an orange colored, in-line, 2 cylinder, air-cooled diesel, reminiscent of half of the four-cylinder Onan unit on a de-icing truck I used to service in Alaska. The only data plate I could find was on the generator head. It was an Almond, 6 kw, 1800 rpm unit. I found many Allmond light plants on line but nothing on this particular unit, or engine. It had no battery and was buried among other assorted contractor cast-offs. I was assured that it “worked” 2 years ago when it was parked there but I passed—to my loss—I now suspect.

      Care to comment?

  8. Homealone777 says:

    I remember, 5-10 years ago; Around here, unless it was in big truck or bigger pickup
    truck; Nobody cared much about small diesel’s. Boy, Look at it now! What I could find so easily then and decently priced, has almost disappeared! Even in the junk yards, it’s like
    finding a hidden treasure! And the price is in the ceiling! Now, almost completely out of my reach. Just a few years ago I could have had about anything I wanted…I guess hindsight truly is 20/20. But with the Lords help; I’ll get there.

  9. Paul Karpfen says:

    Is there a relay to push to get the fuel pump to prime the engine? I just picked up one of these which had been sitting around for a few years. A friend helped with getting it going – we decoked the head and put it back together. He got it going playing with the fuel screws to let the old fuel out. One thing was that he had to hotwire the fuel pump as when you pushed the start button it wasn’t priming the engine.

    I was on this board earlier asking about a lister that had come available – but that was beyond my price point and as a neophyte to old reliable engines a bit of a pipe dream. I’d been looking for a generator to power our house in outtages and wanting to avoid what my wife would get – a big box type generator … and liked the look of the onan 6500 w rv generators – that at least ran at 1800 rpm rather than 3600. One showed up on Craigslist – I took a bit of a leap of faith as it wasn’t running and was in storage and I didn’t know the model of it even. My friend told me its an old cck from the 60s. Now that it’s gotten running I need to give it a home, put the muffler on, change the oil and filter and spark plugs – and see how it runs the house. I’m glad I just happened upon a keeper (for $350) … when a lister was a bit beyond me (at $3500).

  10. Fred David says:

    Hi Harold

  11. Robert B. says:

    Looking for a sassoon choke control unit for a 5.0 CCK Onan GenSet. Any help would be appreciated. Thank you.

  12. phill manley says:

    a friend recently cam into a onan gen set 5OCCK with battery start. also has manual rope start. Any info would be helpfull, was in good running order 5 yrs ago. Thanks = phill

    • George B. says:

      I may have mentioned that a website called smokestack has quite a bit of info on CCKs, the other thing i did mention is Cummins bought up Onan, and my local dealer went out of his way to help me find parts and even drawings for this old machine, hats off to Cummins.

    • larry burke says:

      I can’t say I’m well versed on the Onans, as I’m just starting out. I will say I’m overly impressed with my CCK and see lots of potential in it. Though as George B. states, the gas mileage is atrocious. However, there are a few remedies I think I’ll try before conceding defeat on that issue.
      I’m a retired auto mechanic, living ‘off-grid’ and the CCK is my lifeline until I get my waterwheel on-line. So it is essential that it runs well.
      When I got it, the guy who had it didn’t know much about engines in general and I have had to re-do much of his wiring on the 120VAC side, as he simply had taken bare wires and twisted them together when he removed it from the RV to become a free-standing’ unit. Much is missing too. Still, it runs and operates well. That is except for a few glitches. There is an aftermarket electric fuel pump on it, connected to a 1 gal. makeshift gas tank that came off of a pressure washer unit, and had no filters what-so-ever, which created immediate probs. with the carb. Of which I have removed several times and cleaned the needle & seat, power circuit etc. Fortunately, they are very simple carbs. and have only needed to remove the top. The intake manifold must be removed to get to the bolts underneath the carb base, but still, even if needed, that won’t require much.
      I’m learning as I go, and right now my problem is that it doesn’t charge the batt. It gets it’s 12V circuit from internal fields in the gen. but otherwise is similar to an older style auto system with a separate voltage regulator. Of which, very little information seems forthcoming, at least via the net. So once again, I’ll try my trial & error approach and see what happens.
      I wouldn’t mind that way normally, as I have found you really learn a system thoroughly by playing with it. But the other side of the coin is you can make some costly errors too.
      Regardless, if you experience any problems, I’ll try to help as best I can and maybe by that time I will have gone through the entire generator/engine.
      Good luck

  13. philip o'dowd says:

    I am new to old generators but am searching out my options and keep coming across the Onan CCK, CCKA, CCKB designations. I am curious. What do the letters stand for, if anything except the model designation?

    • George B. says:

      Might as well stand for old, outdated, and less efficient.. these are flatheads and they don’t exaclty sip fuel. They do however run forever and make great standby units, don’t ever think you’ll be happy with fuel consumption. There are better picks if you plan to run the hours.

  14. larry burke says:

    I was so desperate for a manual that I clicked on the ad for free downloads and now can’t remove the toolbar they placed on my computer, and besides, it is not what they say it is.

  15. Dave L says:

    I found one of these old gems in a 139 year old farm house back in the shed. After talking to the owner he said when he purchased the house it been there for over 20 years he’s owned the house its been there. After getting it home and cleaning of the carb tank etc I was pleased it runs like a champ. I love the way it hums while running not sounding like these new generators now a days. Boy they just don’t make things to last anymore.

  16. larry burke says:

    Since my last post, I have been running this old cck, and true enough as George B. says, it doesn’t ‘sip’ gas. But this old guy starts every time in less than a full revolution, IF the battery is charged. But that is the problem I’m having. Not being familiar with the entire set-up, all I know for certain is that I am not getting more that 12.4VDC coming off any terminal of the regulator. On the older vehicles, where the regulator was not integrated with the alternator, there was a procedure to check the operation of each unit separately. However, they didn’t have all these ceramic resistors that I’m seeing on my CCK, all of which, in one way or the other, connect to the regulator directly or otherwise.
    One of which has a coil winding external that appears to have a break in it. But each of these resistors, when I checked the voltage while the eng. was running, showed 19 VDC on at least one terminal.
    I recall some older type regulators being adjustable by way of the spring tension to the contacts. Still, I haven’t a clue as to the effect these resistors have in relation to it.
    But the bottom line is, I’m not getting enough voltage directly from the regulator to charge the battery. Anyone familiar enough with these monsters to guide me?

  17. Bryan says:

    G’day Guy’s
    On the subject of Onan’s I have this old one here with a fully rewound 15KVA single and 3 phase gen head attached. The onan motor is a 4 cyl air cooled and it runs on autogas. Just went up and had look and the nameplate for the spec has worn away so model number in unkown. I was told this unit was used on container ships for refrigerated containers and it has the space for 3 gas bottles.

    Now as No.3 cyl is gone on the motor( well serious head issue) and the fact no spares can be sourced like dizzy cap points etc the motor is destined for scrap metal.

    Would anyone have any idea as to what speed these units run at as I would like to find a new motor (possibly a 20/2) so I can get that genhead back to life so when big machining jobs comeup I’m not limited with my shed RE system.

    Regards Bryan

    • George B. says:

      It may depend on country, if made in this hemisphere, it’s likely 1800 rpm.

      In your country, 1500 rpm, the stock head would have said whether it was 60hz or 60hz, and would have given number of poles, all of these are related to RPM.

  18. Dean Shultis says:

    I have a 1985 vintage Onan 4.0 CCK-3CR/2260H in my boat. Not only would I like to find parts, I’m seeing that the electric choke is not working. It appears that +12vdc is on always on the choke and when you start, the ground path is applied. Not sure of that path. Does anyone know where I can get the wiring diagram for that circuit?
    Thanks, Dean

    • George B. says:

      Dean, a few searches should find it, there’s a CCK expert that visits here, otherwise, go to your local Cummins dealer, or call the one in Renton Washington. Very helpful peopel there, and I was amazed how well they were supporting old Onan products. these old Onan units are kiss, it’s likely there’s one relay that brings in the ground to take off the choke, if you wern’t in sucha tight space, you’d likely have foud it on your own.. But that’s a guess, and not all CCKs are the same.

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