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Rough Running.......need help.

in 912 / 914 Technical Questions 10 years ago

  • Re: Rough Running.......need help.

    by » 10 years ago

    Did you have the problem before the carb rebuild? Maybe something in the carbs was missed or installed wrong.

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

      
    Report

  • Re: Rough Running.......need help.

    by » 10 years ago

    I have had this problem since I have had the plane. I just bought it in May and have been trying to fix in since then. The engine has 500 hours on it now.

    I did a full teardown of the carbs, all O-rings replaced along with jets, needle jets, diaphrams. The only thing not replaced was the springs.

    I always get the vibration you can see in the Lexan. The seat of the pants vibration(which is different) is not consistent though. Some days it seems worse than others. It is more like a low frequency rumbling and usually feels worse in a descent.

    Travis
      
    Report

  • Re: Rough Running.......need help.

    by » 10 years ago

    There is some normal vibration in most aircraft and some feel it differently due to the type of aircraft materials. Could this just be its normal vibration?

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

      
    Report

  • Re: Rough Running.......need help.

    by » 10 years ago

    I not want to steal this thread but add my own story to help.

    I have also rebuilded my carbs, every part but not slides or springs. Springs had length 120mm, same as new spring. I even take out new parts and fit old parts as double test but still rough running is present.

    I hope to borrow 2 carbs to test. I wonder if slide is sticky and make mixture wrong. I not have EGT sensors which would help much.

    I have also run motor with exhaust removed, rough running still happen.

    Prop balance and blade angles all good. Rough running is still happens with prop removed (careful with speed).

    My gearbox has new inside parts, prop shaft, dog gear, bearing and springs.

    If I test borrow carbs, I report my results to help.
      
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  • Re: Rough Running.......need help.

    by » 10 years ago

    At first I thought maybe it was just normal engine/airframe harmonics issue, but after flying for about an hour on a cross country I just cannot imagine this being very normal.
    I am intrigued about the barry mounts, as when I replaced them I thought that it felt slightly more harsh afterwards. The mounts did not come with instructions so I tightened them down as far as possible. Aren't they supposed to be fully compressed (tightened)?

    I have ridden in another rotax 912 aircraft and felt no vibration at all. Mine has the vibration and it feels like the engine is missing or stumbling upon itself but listening to the engine you cannot hear any difference, it is very strange. Everything I can think of keeps pointing me back to the carbs but I don't know what to do next.

    Travis
      
    Report
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