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  • Re: fuel coming out of vent tubes

    by » 6 years ago


    What type of aircraft? are the carbs and manifolds swapped to the outboard position like a Kitfox 4?
    maybe the carbs are shaking too much?
    Are the pneumatically carbs synced at idle?
    Idle too low?
    Engine mount weak (not containing torsional vibration)?

  • Re: fuel coming out of vent tubes

    by » 3 months ago


    Hi Roy! Did you ever get this problem solved? I am having nearly the exact same issue. Carb vent lines are leaking fuel after carb rebuild. Floats are within specs and they float, also replaced viton tips in both carbs.

    We thought we fixed everything and got thru a carb sync and everything ran perfectly for 10 minutes. Started up the next day for a test flight and the engine ran rough and then started leaking out vent tubes again!!

    We are out of ideas!?!


  • Re: fuel coming out of vent tubes

    by » 3 months ago


    Hi Ian,

    This may be the float brass armature is not adjusted properly or the needle valve isn't shutting off the fuel. I have saved several carbs from this by polishing the needle valve seat.


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


  • Re: fuel coming out of vent tubes

    by » 3 months ago


    We are currently soaking the carbs in Berrymans to possibly and hopefully fix that seating issue..  what did you use to polish?


  • Re: fuel coming out of vent tubes

    by » 3 months ago


    Ian, just a thought, have you double checked the bowden cable and housing installation. If the housing(s) have leeway to move even a little you get all sorts of vibration despite a preliminary good sync - it just won’t last. If the housings are not firmly fixed (with no leeway) syncing carbs is a game one cannot win.


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