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new carbs venting fuel at 2500rpm and below

in 912 / 914 Technical Questions 13 years ago

  • Re: new carbs venting fuel at 2500rpm and below

    by » 13 years ago

    Don,

    The floats sit with very little of the float submerged. When you remove the bowl, notice if the floats are both about the same height while floating. Lift them out and shake them and you will know right away if any fuel is inside the float. If you can carefully remove the bowl without spilling any fuel, lift the floats out and the fuel level should be about 1/2" from the top of the bowl.

    Bill.
    Thank you said by: Don Hudgeon
      
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  • Re: new carbs venting fuel at 2500rpm and below

    by » 13 years ago

    Hi Bill
    Thanks for the information. I did not get down to the hanger today. Hopefully tomorrow.I suppose if the floats are porous at all they should have some fuel on the inside. I sure did not notice any last week when I changed the float valves.
    Thanks again.
    Don
      
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  • Re: new carbs venting fuel at 2500rpm and below

    by » 13 years ago

    I got to the airport today. The floats sink down almost to the "arm pins" (very close to half way submerged). The fuel level with the floats in is about 1/4" from the top. With the floats out is closer to 1/2". I talked to Rob (mechanic at Rotax in Vernon) and he says they should sit quite high in the fuel.There was no fuel inside that I could tell just by shaking.
    Today I ordered 4 new floats. Sure hope that was the problem. This issue (spitting fuel) came on with no other changes to the engine so I guess it makes sense if they just kept sinking a bit over time. They are original from a mid 90`s engine.
    Crossing fingers.
    Don
      
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  • Re: new carbs venting fuel at 2500rpm and below

    by » 13 years ago

    Hi Don,

    Your floats sound okay. I don't feel the new floats will help. I just did a hose change yesterday and a little rubber hose debris the size of a pin head got into a carb. It caused rough running and fuel venting plus the carb balance was a PITA so I knew right away where my problem was. Once the plane starts shaking the fuel may vent because the floats can't do a good job controlling the level while shaking.

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

    Thank you said by: Don Hudgeon
      
    Report

  • Re: new carbs venting fuel at 2500rpm and below

    by » 13 years ago

    Hi Roger
    When I had the carbs off to change the float valves I looked at the cleanliness quite closely. Just in case though, I sprayed carb cleaner on all parts including in all the jet orifices (everywhere else too) and then used air pressure by blowing in each of the holes. I did not remove any jet seats though thinking the 100 pounds air pressure would remove any possible contamination.
    Back to the float question. Are you saying that it is quite normal for the floats to sink about half way up. The float arm pins were pretty well right at the fuel surface. Is this normal?
    Thanks for your comments
    Don
      
    Report
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