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Full Engine Power

in 912 / 914 Technical Questions 13 years ago
I have a 912uls which used to develop full power on takeoff (5500rpm - 4500ft alt) and the full 5800rpm straight and level at 8000msl. I now will only develop 4800rpm on takeoff roll and in climb. After being in flight for 15+min, I will get the full 5500rpm. I have not changed prop pitch, I have rebuilt the carbs, exterior fuel filter clean, air filter clean, fuel hoses recently replaced, fuel pump inspected and found good condition, using 91 octane motor gas, engine brought up to 120 degrees before takeoff (and oil pressure 60 lbs. I have no idea as to what the problem is. Any help would be appreciated. Thanks, Jeff

  • Re: Full Engine Power

    by » 13 years ago

    Hi Jeffery,

    Since you just worked on the carbs and providing everything was okay before you did the work the carbs is where I would start. If you fuel starve the engine it will react just like you described. You either blocked a fuel line, a filter or did something inside the carb. Since you just replaced the fuel hose, check the carb bowls for debris. I am seeing this quite often with hose change. If you have small flecks of black debris you can try and pull the bowls and flush the carbs some, but if that doesn't work you can spend a week and chase a ghost and spend lots of hours scratching your head or pull the carbs back off and really flush the passages out with carb cleaner in a can with the jet spray and then blow them out with some air and be done with it in an hour or two.
    If you have black rubber flakes in the carb bowl then it came from the hose from the fuel pump that goes to the carbs. There is a screen in the fuel pump and it is a fine mesh so it didn't get past that. If you have a gascolator then that would have been another screen point.
    Out of 20 some hose changes this has happened to me 3 times. Now I just protect myself from it happening.

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

      
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  • Re: Full Engine Power

    by » 13 years ago

    I experienced an identical problem about 50 hours before an engine failure during takeoff. The cause of the failure was not determined by me. I suspect it was the old carburators that I have since replaced but I actually will never know. My carbs were about 12 years old but only had 250 hours on them when I experienced my failure, wish I knew what happened. Hope you find out.
    P.S. I fly a 912F on my Kitfox. The plane did not have a fuel return line. That is being rectified as we speak.
      
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  • Re: Full Engine Power

    by » 12 years ago

    I am having a similar problem on my 914 with about 200 hours on it. Did the carb clean fix the problem?
      
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  • Re: Full Engine Power

    by » 12 years ago

    Hi jeff,

    Yours could be fuel delivery or a sensor.

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

      
    Report

  • Re: Full Engine Power

    by » 12 years ago

    Roger:

    Thanks for the response. I am embarking on rebuilding the carburetor, which are due anyway and testing the fuek regulator. Which sensor(s) are you referring to.

    Jeff
      
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