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Hi to all!
I have a 912 Uls 100 with 300
Hours TT. Ocassionaly in flight I would get whiff of fuel, I run
93 auto fuel. Then when I use
100 LL aviation nothing. I checked all fuel fittings, replaced the distribution block, it was leaking and things were normal again.
My oil was due for a change
And when I removed the cowl
I could smell auto fuel. Further investigation revealed
The number 2 carburetor was
Weeping fuel from the hot air
Duct down the scat tube. I removed the carb and checked the the floats they weighed in at 6 grams total.
I replaced the bowl gasket and reinstalled. The engine idled fine and runs great. Bad news it's weeping fuel again.
If I don't stuff a rag in it it will
Drip enough to start a puddle on the hangar floor. I am lost
at the moment and seeking
Some guidance. I have the old floats which weigh in at 5.7
Grams put they have been dried out since May when I did the float replacement.

Thanks everyone for your help.

Bob Strakele
RANS S7S
N854K
  • Re: fuel seepage from 912 100hp carburetor

    by » 7 years ago


    I am not familiar with your particular installation but let me suggest some general ideas.

    If the carb is leaking fuel while hangared, it is generally caused by the float bowl overfilling.
    This can be because the floats are not floating, which you have apparently ruled out,
    Or because the float valve is not sealing.
    I would look at the float valve as the next possible source of the problem.
    It could have debris blocking it or the seal may have seen better days.
    It might also just be loose and seeping fuel past the threads.

    When you initially remove the carb bowl, hold the float up loosely with a finger.
    The float valve should seal with extremely little pressure, don't push aggressively.
    You should not have any fuel dripping.

    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    Clicking the "Thank You" is Always Appreciated by Everyone.


  • Re: fuel seepage from 912 100hp carburetor

    by » 7 years ago


    Hi Bob,
    I fly the 80 HP Rotax. When the bowl is full of fuel, the float pushes the arm up to stop fuel from flooding. Are your float arms adjusted to specs with the Rotax Manual. Could there be some dirt in the needle seat area keeping it from seating properly? Is there evidence of fuel in the carburetor Vent tube? Do you have a gascolator and can you see if there is debris in the bowl? Just some ideas. Do you have a pic of the installation?
    Wheels

  • Re: fuel seepage from 912 100hp carburetor

    by » 7 years ago


    Hi, no evidence of dirt in carb bowl. Vent tubes show
    No fuel. I have a gasolator which I will check today.
    I haven't checked the specs
    For the float stop since nothing has
    changed other than I replaced the floats in
    May of this year. I will get a few pictures of the installation. Thank you for your help.

    Bob

  • Re: fuel seepage from 912 100hp carburetor

    by » 7 years ago


    Hi Bill, thank you for your input. I will check it out today. The floats meet the spec of less than 7 grams,
    6 to be exact. I think we are on to something with the float stop or some particles
    Holding it up. Going to check gasolator astvsame time.

    Thanks, Bob

  • Re: fuel seepage from 912 100hp carburetor

    by » 7 years ago


    HI Bob.

    I have had this same problem for years. I went to great lengths to solve this problem but it persists. On the advice of another member I just close the fuel valves. It will only leak overnight through the float valve of either carb.

    Alan

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