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Rebuilding an Onan motor.

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13 comments

  • Forkliftking
    Parts aren't all that expensive. I overhauled an onan opposed cyl. engine on a welder last summer for about $125.00. Rod caps go on at an angle. First rods that I've ever seen like that.
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  • peabo
    Onan engines were bad to get a carbon build-up in the cylinders. Is it making a knocking sound?
    You may want to pull the heads and see how much carbon is on top of the pistons and the heads. Clean that off and check the compression again. May not need a complete overhaul. Let us know what you find.
    It's been a long time since I worked on one so take this with a grain of salt.


    Thanks---Peabo
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  • Cutiegirlracing
    If it has carbon build up, there is this stuff, I can't remember the name, it's for car engines, you spray it into the engine, in each spark plug hole, let it seat over night and then start and rev the engine and it suppose to break the carbon up and clean it out. Question is can't I just use that? It's not knocking or anything. It still has good power, I puller a 5000 pound boat, it smoked more than usual but it pulled okay.
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  • Kimbercolt
    My dad and me rebuilt his sears suburban garden tractor, we replaced the old 16 with a onan, I found him some chevon tires off an atv, by god its a real tractor now, Bigger engine, bigger tires, got love the power
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  • dcon12
    quote:Originally posted by Kimbercolt
    My dad and me rebuilt his sears suburban garden tractor, we replaced the old 16 with a onan, I found him some chevon tires off an atv, by god its a real tractor now, Bigger engine, bigger tires, got love the power



    The Sears suburban tractors were powerful little tractors in thier day. They also have a fan base with collectors and a website. Don
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  • rogue_rob
    quote:Originally posted by Cutiegirlracing
    If it has carbon build up, there is this stuff, I can't remember the name, it's for car engines, you spray it into the engine, in each spark plug hole, let it seat over night and then start and rev the engine and it suppose to break the carbon up and clean it out. Question is can't I just use that? It's not knocking or anything. It still has good power, I puller a 5000 pound boat, it smoked more than usual but it pulled okay.


    you can use "Seafoam" on it. I hear that stuff is VERY good for doing a top-end cleaning of engines. In my truck, I just let the whole bottle suck in through the PCV vaccum hose. Turn the truck off for 15 minutes and then start it back up. You should see all the smoke!
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  • Cutiegirlracing
    Wouldn't carbon build up in my engine cause a higher compression reading due to the smaller air space in the cylinders? You guys that have done the rebuilds, where did you get your parts?
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  • Cutiegirlracing
    quote:Originally posted by dcon12
    quote:Originally posted by Kimbercolt
    My dad and me rebuilt his sears suburban garden tractor, we replaced the old 16 with a onan, I found him some chevon tires off an atv, by god its a real tractor now, Bigger engine, bigger tires, got love the power



    The Sears suburban tractors were powerful little tractors in thier day. They also have a fan base with collectors and a website. Don



    I had one that I restore and sold a few years back. I was a smaller one with a 8 horse B&S. I'll have to try to find some pix of it. There is a very good fan base for the Sears though.
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  • scrumpyjack
    There are Onan dealer networks out there. You can also go to your local John Deere lawn & garden dealer. The JD 316 tractor was a big seller, equipped with a 16hp Onan. The JD 318 is still to this day, one of the all-time greatest sellers for JD.

    If you decide to do anything to it, which if it's not broke....don't fix it until it is, be sure to copy all of the info from the data plate on the engine and take it with you. If you go to an original OEM dealer for the brand of tractor, take the tractor serial number with you as well. Your parts person will love you for it.[:D]

    What brand and model tractor is it??
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  • A J Christ
    Cummins/Onan will sell you all the parts you could need, all at a premium price. Look around and you'll find some other sources. Very common engine, lots out there. Good solid reliable, well made.

    Onan sells some stuff goes by the name of 4C that is designed to clean out the carbon. Just follow the directions on the can, good stuff.

    Have been in a lot of them, nothing odd or unusual about them.
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  • buddyb
    Are Kohler and Onan the same?I rebuilt a 12 HP Kohler a few years ago and parts were pretty expensive.If I remember correctly I paid about a 100 dollars for a piston and rod.
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  • v35
    The Aux gen set in my camper makes cranking noises but doesnt seem to rotate the engine.
    It's an NHM, essentially sealed in a box that prevents you from seeing
    much. I suspect an RV shop sabotaged it.
    Any hints on getting at the starter without dropping the whole MG set?
    I googled Onan and found lots of parts plus some listed on Ebay.
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