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Carbs Leaking

Category: General Tech Discussion 3 months ago

Client aircraft's 912 CV carbs started leaking, both of them.  It's a tricycle gear Highlander.  Replaced the float needles and ensured the float arms are the correct distance from the base of the carbs.  Still leaked after reassembly.  Looked back in where the float needles seat, no visible deformities.  Weighed the floats, they are within spec.

Chatted with the Pro Carb guys in Kansas, their suggesting would be to next replace the seats.  Not sure we're there yet.  Would have to tap them out and press in new ones.

I have another set of new floats that I'm going to try, but any other suggestions on what to look at?

  • Re: Carbs Leaking

    by » 3 months ago


    Are the carburetors synchronized? If not vibrations may cause the needle vales to unseat. Fuel pressure over 7 psi will also cause leakage. Are the carburetor vent lines properly installed.


  • Re: Carbs Leaking

    by » 3 months ago


    Bowl gaskets properly seated?  I prefer the newer composite-style gaskets as opposed to the earlier cork gaskets.


  • Re: Carbs Leaking

    by » 3 months ago


    As David asked,  Is it leaking from the Bowl, or is it dripping out of the Carb Throat?

    Exactly where is the leak originating from???

    Does it drip with the engine running or is it only noticed when stopped?


    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    Bill.Hertzel@Yahoo.com
    Clicking the "Thank You" is Always Appreciated.


  • Re: Carbs Leaking

    by » 5 weeks ago


    Update, still an issue.

    Owner told me the carbs had old rubber, so I did the 5 year on them and replaced all the rubber components.  The owner reinstalled the carbs himself, did a run up and afterwards they started leaking again.  Does not leak when engine is running.

    Per the owner (I have not had a chance yet to go to the airplane), the leak is coming from where the air filter connects to the carb.  Per the owner, they did not do a static balance yet.

    Looking for suggestions on what to look at next.  I've asked the owner to do the balancing.


  • Re: Carbs Leaking

    by » 5 weeks ago


    Since it's coming out of the air intake side it could be heavy floats or the brass float armature that the floats push on are out of adjustment or the needle valve has an issue. If the floats aren't too heavy then the carbs need to come back off. Somebody missed something.


    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-574-1080 Home (TRY HOME FIRST)
    520-349-7056 Cell

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