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912 ULS float valve overflow overflew

in 912 / 914 Technical Questions 7 years ago

  • Re: 912 ULS float valve overflow overflew

    by » 7 years ago

    Pull the bowls and weigh the floats even if you have fairly new ones. Then you may need to pull the carb and turn it upside down and make sure the float armature that the floats ride on is at its proper height. It is possible that the needle valve is bad, but more likely the other two items may be the offender.
    You can play around for another week, but the sooner you check these items to sooner the problem gets fixed or at the least you rule them out.

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

      
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  • Re: 912 ULS float valve overflow overflew

    by » 7 years ago

    I weighed the floats in the leaking carb and they came to 11.7g so I definitely need to replace those. Will order them this week and I expect I'll be able to have them in and try again next weekend.

    I'm curious how they can get to weigh so much - how does the fuel get in?
      
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  • Re: 912 ULS float valve overflow overflew

    by » 7 years ago

    When the floats sink that allows more fuel to flow and makes idle rpms too rich and flood the carbs. You may have fuel coming out the vent tubes.
    The floats are made of millions of tiny air bubbles and each seal themselves from fuel absorption. If the material composition is wrong then fuel can penetrate the float over some time and they loose the ability to float and slowly start to sink and fail to control the fuel level in the bowl.

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

    Thank you said by: RotaxOwner Admin
      
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  • Re: 912 ULS float valve overflow overflew

    by » 7 years ago

    Thanks for the explanation Roger, makes sense.

    This weekend I got my replacement floats and after swapping them out I'm happy to say that the engine seems back to normal, no vibrations and no fuel out of the overflow. Ran it through a range of RPMs and all seemed good, will do some taxi tests to verify before taking it back up.

    Thanks to you and everyone who made suggestions, all very helpful

    Paul
    Thank you said by: RotaxOwner Admin
      
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