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RPM goes back and fwd 200 RPM while cruising

in General Tech Discussion 10 years ago

  • Re: RPM goes back and fwd 200 RPM while cruising

    by » 10 years ago

    Here is a couple ideas,


    Most likely a carb issue and not electrical. It could be a bad fuel pump (how old is the pump and what make/model?), clogged fuel filter or even an air leak in the rubber carb flange or if around the air intake manifold. Rubber carb flange leaks are hard to see at times. One way to look for an air leak is to use a can of "starting Fluid". Start the engine and let it idle around 1800 rpm. Take the carb in one hand and flex it back and forth and spray the flange with some starting fluid. Don't be afraid to flex the rubber carb flange a little. If there is an air leak the engine rpm will pick up with the induction of the starting fluid. If the carb flanges are over 5 years old they should have been replaced.
    You can then spray a little starting fluid around the air intake manifold joints. If there is a leak the engine rpm will change.

    The fuel pump may not be able to keep up with the fuel flow at high rpms if it is going bad. There is a filter inside the pumps that may have too much debris and or you other fuel filters.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

      
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  • Re: RPM goes back and fwd 200 RPM while cruising

    by » 10 years ago

    Hola Gaetan, I did change the cowling because the old one was heavier, ans was in bad shape.
      
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  • Re: RPM goes back and fwd 200 RPM while cruising

    by » 10 years ago

    Thanks Roger, I will check and let you know
      
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