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Generator Tune-Up - What Have I done?

Discussion in 'Electronic Repair' started by Fred McKenzie, Jul 13, 2006.

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  1. A 2500 Watt 120V power generator (Powermate Proforce PM0102500) seems to
    be working fine, but engine sounds a little rough. Why not touch up the
    carburetor adjustment and see if that improves it?

    First I turned the screw on the carburetor to the right. Some resistance
    to turning, but absolutely no difference in engine speed or sound.

    Then I turned the screw to the left. Screw is quite loose and still no
    difference in the engine, but now I have gas leaking from the bottom of
    the carburetor! I turned the screw to the right until snug, and the gas
    leak has stopped.

    There is no other adjustment visible on this carburetor. Is that screw
    intended to drain the carburetor, or have I seriously messed up something?

    I've searched the web for data, and only found that the 5.5 HP engine was
    made by "Sumec". I gather that they make motorcycle engines, but found no
    carburetor data.

  2. Well, if the screw is about a #8 and has a o-ring and pointy end and
    screws into the main body of the carb, it probably is a mixture
    adjustment screw.

    If it's bigger, has a flat rubber or fiber washer, and screws into the
    float-bowl, it's probably a drain screw.

    In any case you'llprobably get better answers on a small-ening
    newsgroup, not an electronics group.
  3. Probably true, but there are all kind of guru's here that know all sorts of
    things.. I once asked abou the best way to make a glass beer bottle into a
    drinking glass / tumbler and got lots of answers here and almost no answers
    in or whatever the group is for that was. :)

    Answer to the original,

    As Ancient Hacker also said...
    I'd guess that the screw you turned was just a bowl drain since it was tight
    when you tried to turn it to the right. Many small carbs have them, and you
    probably havn't messed anything up.

  4. Mike-

    The screw is located on the side of the carburetor, but at the very
    bottom. Your comment that "many small carbs have them", reinforced by the
    fact that gas did drain, leads me to think everything is OK.

    Following Ancient Hacker's suggestion, I searched for a more relavent
    newsgroup. A semi-close match was, where I posted
    again. Today there are a couple of responses there that don't seem to
    address the carburetor! One refers to an article from the Journal of
    Personality and Social Psychology entitled, "Unskilled and Unaware of It:
    How Difficulties in Recognizing One's Own Incompetence Lead to Inflated

    Those motorcycle guys sure are an intellectual bunch!

  5. Following Ancient Hacker's suggestion, I searched for a more relavent
    I see that you had about the same experience that I did with the glass
    making / cutting community. :)

    - Mike
  6. James Sweet

    James Sweet Guest

    That sounds like the banjo bolt that holds the float bowl on. If you
    loosen it up go figure fuel will leak out.
  7. James-

    There is a hex-head bolt on the bottom that probably holds the bowl in
    place. The subject screw is on the side near the bottom, screwing in
    towards the center of the bowl. It has a small hole on the bottom of the
    tube it screws into, that appears to be the drain.

    I ran the engine with the fuel valve shut off and choke on, to run out as
    much fuel as possible. I removed the screw and there was still a few
    drops of gas that drained.

    The screw has a relatively sharp point and has a spring to keep it from
    vibrating loose. In other words, it looks just like needle-valve
    adjustments on other carburetors.

    Someone on the newsgroup posted a link to which has forums on small engine and generator
    set repairs. If I have any additional problems, that looks like a good
    place to find help.

  8. James Sweet

    James Sweet Guest

    Hmm that really does sound like the needle valve, be careful not to
    crank it down too tight, you can squish the tip. It may be for the idle
    mixture if the engine still runs fine.
  9. Well I'd say it sounded like a needle valve too except that it was tight to
    start with and when you open it gas pours out.. Does the gas come out some
    sort of line or hole in the carburator or does it pour out the hole where
    the screw is?

    An easy way to find out what that screw does is simply to remove it.. If it
    is a needle valve it should come all the way out and look kind of like a
    needle and be pointed on the end.. If not you'll probably have gas running
    allover the place.

    If it is running correctly now I wouldn't touch it though. Too much
    potential to make it not run. If anything I'd take the carb and have it
    cleaned or rebuilt at the local mower shop if it doesn't appear to have any
    other screws on it.

    - Mike
  10. Mike-

    It is a needle valve. There is a small hole, perhaps an eighth of an inch
    diameter, located on the bottom side of the bowl where the needle valve
    screws in. Yes, gas leaks when the valve is unscrewed, even before it is

    There is a paragraph in the owner's manual that says to drain the
    carburetor before storing the generator for a long period. However, it
    doesn't say anything about how to do it. I'm hoping that the subject
    needle valve is intended for that purpose!

    I have an old Sears/Generac carburetor that has two such valves, and the
    owner's manual gives instructions on how to adjust them. One is for
    no-load and the other for full-load, according to the procedure. The one
    on the Powermate generator doesn't behave like either of the ones on the
    Sears/Generac. The engine sound doesn't waver when it is adjusted for
    either load or no load, and there is never any black smoke from the

    For the moment, I plan to leave it alone, as the generator seems to be
    functioning OK. I think the "rough" sound may have smoothed-out after
    running for a while.

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