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fuel coming out of vent tubes

in General Tech Discussion 6 years ago
hello, i have a Rotax 912 ul 80 hp it has two 64 carbs on it and they were rebuilt but fuel is comming out of both vent tubes on the cabs the floats are set corectly at 10.5mm from the base of carb. they have all new parts...help please

  • Re: fuel coming out of vent tubes

    by » 6 years ago

    Have you reviewed this video:

    https://www.rotax-owner.com/videos-topmenu/rotax-minute/454-carb-vent-lines
      
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  • Re: fuel coming out of vent tubes

    by » 6 years ago

    i have.. the fuel is coming out constanty out of both vent tubes while on the ground with the 3 inch tubes
      
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  • Re: fuel coming out of vent tubes

    by » 6 years ago

    Hi Roy,
    Check that both carburators are perfectly vertical, if they are installed in an angle this can cause the neddle float to stuck and you will have a leak at the vents, if the carburators are perfectly vertical and you have a leak at the vent of both carburators you will need to disassemble them again and first check the flotability of each float then check that you don´t have any debris in the float neddle seat and check also the the tip the the float neddles are not damaged.
    I s very strange that both carbs have a float neddle leak and more when they where rebuilt, for sure they are not well assembled.
    If you did the work check it again and before closing the carburator bottom cup, check thta when you push the floats you have a perfect seal of the needle.

    Also check the height of the floats when they push and close the neddle that supply the fuel

    Regards
    Thank you said by: Roy Evans
      
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  • Re: fuel coming out of vent tubes

    by » 6 years ago

    All have been rechecked by myself irmt-A and another a&p irmt again restarted and again fuel coming out of vent tubes... Is possible that the fuel pump is putting out more than 7.5 p.s.i. causing this problem?????
      
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  • Re: fuel coming out of vent tubes

    by » 6 years ago

    I don´t think so, check the flotability of your floats
    Your fuel pump will give you about 5.5 psi and with this pressure and even with about 8 psi a good pair of floats and the needle valve will not open and this pressure.
    Are you sure you installed the seat of the needle valves or your teied to clean the seats that maybe you damaged the seats of your needle valves of the floats?
    Here I have some carbs, I will make a test at how much pressure they will open
      
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