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Honda 15 spark plug fouling

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  • Honda 15 spark plug fouling

    I bought a pig in a poke on ebay -- 15 hp extra long shaft which fouls plugs so bad after 15 hours engine will not run. Cleaned carb, replaced mixture screw -- set to about 1/2 turn out now. Compression about 170 psi -- a little high. After short run time on new plugs they are classically fouled with carbon.
    Folks suggest running full throttle to prevent fouling.
    Other suggestions?

  • #2
    Re: Honda 15 spark plug fouling

    I don't think gas by itself will cause fouling that fast. How is your oil level? That is probably the same as my 15hp Honda and I have never had a problem with fouling.
    What does the area below the exhaust look like on the rear of the engine? If it is really smoked up w/black crap on it then you are running too rich on gas. A 1/2 turn doesn't seem like it it out enough, but then I don't know that. Have you checked the float level in the carb?
    I am having some problems w/my 15 but not fouling plugs.


    • #3
      Re: Honda 15 spark plug fouling

      Once again it would be nice to know if you have a 15a or 15d as the end advice can be substantially different.Those compression #s are approriate either way.You will need to determine your idle speed either way as well,with an actual tach.15a set at 1100 warmed up in neutral,15d ,950,but give them a little longer to warm up.Idleing these units too slow or lugging them will cause your exact symptoms.What application are we useing here?


      • #4
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        Re: Honda 15 spark plug fouling

        Thanks for replies -- sorry -- been out of pocket.
        Yes upper exhaust port gets dirty when running.
        Will double check float level.
        Oil level unchanged in 35 hours of running.
        Last edited by seajackski; August 8th, 2008, 01:43 PM. Reason: add info