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Re: Onan generator in 1984 Allegro

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  • J Carlisle
    Happy New Year all,, Since generator questions came up, I have one. On a 67 Travco, I have an Onan, orginal that is powered from a small 4 cyl flathead
    Message 1 of 8 , Jan 1, 2007
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      Happy New Year all,,
      Since generator questions came up, I have one. On a 67 Travco, I
      have an Onan, orginal that is powered from a small 4 cyl flathead
      engine. The previous owner said when he went to start it one day
      there was a loud pop from around the switch box, or just behind it
      somewhere. I have yet to track anything down that may have shorted
      out. Is there anywhere I should be looking or something I should be
      looking for? It is the 6500W model. I have removed the cover from
      the switch box where the toggle switches are and even replaced one of
      the switches but nothing.
      Thanks for any help



      --- In classicrv@yahoogroups.com, Richard Stratton <rstratton40@...>
      wrote:
      >
      > Some thoughts to consider.
      >
      > I repair Generators for a living and from what you are
      > saying I would have to agree with others that you have
      > a carburetor issue.
      >
      > It is my experience that a simple "Carb cleaner"
      > treatment will not do what you want. I suspect that
      > the gen set has been left sitting for some time (more
      > than three months) with fuel in the tank and
      > carburetor and that it has deteriorated to the point
      > of creating a gummy substance in not only the float
      > bowl but also the jets and fuel passages within the
      > body of the carb. These fuel passages are only
      > slightly larger than a human hair and can clog very
      > easily. It is likely you will need to remove the carb
      > from the engine and soak it in a good carb leaning
      > solution for a few hours or more then carefully clean
      > all the passages using compressed air or a spray type
      > cleaning solution. DO NOT use any type of wire other
      > than perhaps a copper wire to clean out the passages.
      >
      > If you find any hardened lacquer type deposits on the
      > bottom of the float bowl you can count on letting the
      > carb soak over night in a good carb cleaning solution
      > and even then it will require carefull cleaning to
      > clear all the small passages.
      >
      > I really suggest you turn this problem over to a small
      > engine repair shop that has staff who are familiar
      > with generators as the govenor settings are very
      > critical and specific to generators as opposed to
      > other small engine applications. Not only that but
      > even the cleaning process is tricky as there are some
      > non metalic parts in the carb that should be removed
      > before using the carb cleaner. Carb cleaner and non
      > metalic parts don't get a long!
      >
      >
      > --- elvislopez35010 <elvislopez35010@...> wrote:
      >
      > > Generator cranks and runs but the governor starts
      > > hunting then the
      > > motor runs rough or even back fires then goes dead.
      > > Sometimes it will
      > > run fine for ten minutes then you turn on the air
      > > conditioner the motor
      > > starts to run eratically then smooth out but will go
      > > dead shortly after
      > > that. I have tried carb cleaner and tried to adjust
      > > the carb. The Mix
      > > adjustment has no affect on runability. Can anyone
      > > help?
      > >
      > >
      >
      >
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    • ned.crv@edwordsmith.com
      ... Isn t the air filter back there behind the controls? A backfire at the carb would be heard at the air filter. Personally, I would ignore one backfire, but
      Message 2 of 8 , Jan 1, 2007
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        J Carlisle wrote:
        > Happy New Year all,,
        > Since generator questions came up, I have one. On a 67 Travco, I
        > have an Onan, orginal that is powered from a small 4 cyl flathead
        > engine. The previous owner said when he went to start it one day
        > there was a loud pop from around the switch box, or just behind it
        > somewhere.

        Isn't the air filter back there behind the controls? A backfire at the
        carb would be heard at the air filter.

        Personally, I would ignore one backfire, but carb backfires have the
        risk of sending flames into the engine compartment, and that's where
        your fuel lines and filters and stuff are, right.

        Carb backfires mean you have fuel being ignited while an intake valve is
        open. This might be due to mis-set ignition timing, but since the
        Onan's ignition timing is fixed and can't be adjusted (if I remember
        correctly), that would be the last place to look. A better bet would be
        to do a leakdown test. Briefly, this test pumps compressed air in
        through a test fitting screwed into a sparkplug hole. If the cylinder
        doesn't hold the compressed air, you determine where it is leaking by
        listening to the exhaust system and the intake system. A leaky intake
        valve will sound like a hiss at the carb/air filter. If that's what
        you've got, you can probably fix it with some wrenches, a few gaskets,
        probably a new valve/spring/guide, and a little bit of work by a
        machinist to prepare the cylinder head.

        By the way, I saw a leakdown tester at Harbor Freight for $39 a couple
        of months ago. They also sell a portable compressed air tank that you
        refill from a gas station air pump. With these two things and a
        sparkplug wrench, I think you could do a leakdown test on a generator
        cylinder. Being a small-budget shade-tree mechanic myself, I made my
        own leakdown tester several years ago from parts I got in the air
        tools/compressor department at the local home fix-it store. Here's a
        link to a good description of how to make the tool and use it:

        http://www.xs11.com/tips/misc/misc3.shtml

        Drilling the 1-mm hole was the hardest part. The tiny drill bit is
        commonly available, but boy howdee, they break easily. It took me three
        tries to drill through the epoxy plug without breaking the bit. Of
        course, a drill press would help, but anyway who has a basement big
        enough for one of those? You might ask at the autoparts store where to
        find a machinist to drill it, if you don't want to hassle with doing it
        yourself.

        Good Luck!

        Ned Bedinger
        Southworth, WA
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