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I experienced an engine hesitation when I was practicing wheel landings. I had the mains firmly planted on the deck, and when I pushed the throttle forward, the engine hesitated noticeably. it quickly came up to speed, and I left the runway in a normal climb out. I am surrounded by Farmfield, so was not concerned about potential need for a landing site. I repeated the exercise two more times with the same results. The carburetors were rebuilt by me Eight hours ago with a full rebuild kit, including floats.

I’m running high test, car gas.

carburetor sync is very good, and smooth from idle to full power. Any ideas

  • Re: 912 UL hesitation

    by » 4 months ago


    I hope I am not offending you when I say it sounds like your throttle movement is a tad to fast.


  • Re: 912 UL hesitation

    by » 4 months ago


    Not offended! Never even thought of that. Other than that the engine is running flawlessly, and I am quite happy with it. Thank you very much. I will pay attention to my throttle technique when I fly next.


  • Re: 912 UL hesitation

    by » 4 months ago


    I had similar symptoms once that turned out to be a small piece of debris in the float bowl that was getting sucked into the main jet. It looked like a small piece of rubber, perhaps from a fuel hose. It might be worth dropping the bowls to take a close look.


  • Re: 912 UL hesitation

    by » 4 months ago


    Consider that the Operating Handbook for every reciprocating engine, not just Rotax, encourages 'smooth application of power.'  The reason for this is to prevent an over rich condition (too much fuel) from abrupt throttle advance which will cause your (any) engine to stumble until the fuel/air mixture resolves to the ratio compatible with the throttle setting.

    Farm fields or not, this is important in a touch and go, or more important in a go-around situation where you need your Rotax to pull you out of your canceled landing without hesitation.

    Taking you at your statement that things are properly installed and calibrated, the required adjustment might be in the speed of your hand.  In any take-off or balked landing, power is your friend, and all that's available to you will be found in the prompt, but smooth advance of your throttle.  Too fast, and you gag your powerplant with too much gas.

    If this still happens after a practice run or two, you likely have a contamination issue from your recent work, something you may want to investigate first before flying.

     


    Thank you said by: jay white

  • Re: 912 UL hesitation

    by » 4 months ago


    Sean, 

    thank you for the quick reply. I neglected to give you a thumbs up, or any commentary before replying to you. Sorry, I should do better with this, although the social media tools tend to be a little silly for a guy my age. I realize after many years of using this forum, that they are actually quite helpful for identifying solid advisors. Thank you again. I will report on my next flight. It is currently 19°F and a strong east wind. The Kitfox has an anemic heater to say the least. I will fly when the temperature is above 30. I’m ID 78 if you’re ever on the side of the pond.

    Cheers  


    Thank you said by: Sean Griffin

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