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   Hello, I have a Rotax 912 and just got my 200hr. Service done. I will add I am a total novice with the engine.  The fuel line that runs across the top and to both carbs had been rubbing a bolt head and had a flat spot.

     I had bought a new line, but the mechanic forgot to replace it.  After I got the plane back in the hanger, I just replaced it myself.  Wasn’t too bad.  I left it to make sure it wasn’t leaking.  It wasn’t, but I never cranked it and have been very busy for 3 weeks.

   Today I was getting it ready for its first flight in the morning.  I was going to crank it just to make sure everything was ready.....it literally sounded like a bugs bunny cartoon.  Slamming, jerking, sounding like it was going to blow apart????? Seemed like one side wasn’t even firing.

 It seemed fine before I changed the line.  The only thing I can think of is air in the system????  This may be totally off base. It was late, so I haven’t even taken the hood off, but hoping that someone could make me feel better about it.  Been grounded for over 8 months trying to get the service done.  Can’t believe I got a problem.

Sorry for the length, and thanks for any help.  thanks again, John

  • Re: Problem after Fuel line change

    by » 10 months ago


    Sounds like Air in the lines.

    If it has been sitting for three weeks, the carb bowls may be only half full.

    Here is the catch;  the bowls won't fill until you start it and it won't run until the bowls fill.

    This is one of the reasons Electric AUX Fuel pumps are recommended.

    If you have one, turn it ON for 30 seconds before cranking.

    If you don't have one, crank for ~20 seconds with the MAGs OFF to pump fuel into the carbs.

    Then try starting again. it may still sputter but it should clear up quickly.

     

    Do not burn up your starter.

    If you need to repeat the process, crank for 30 seconds Max, But wait for 5 minutes before repeating.


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


    Thank you said by: RotaxOwner Admin

  • Re: Problem after Fuel line change

    by » 10 months ago


       Thanks so much for the reply.  I turned it over twice with no mags.  I choked it and it started right up, running smooth at about 2800rpm and full choke.  But, the second I started to let off the choke, it would start getting rough and the EGT on the left side would drop like a rock.???

       It would only run smooth at full choke, and everything looked normal with the choke all the way out.

      I did that before work.  Came back late afternoon and went through the same thing again...same result.  As soon as the choke inches forward, left side EGT drops and it starts getting rough, pull back out all the way and EGT will come back up and match the right.

     

       Is this still air?  Thanks again.

     

     


  • Re: Problem after Fuel line change

    by » 10 months ago


    Sounds like debris in your main jet from the fuel line change.


  • Re: Problem after Fuel line change

    by » 10 months ago


    Your Air problem was gone about 5 seconds after the engine came up to speed.

    This is a different issue.

    The Enricher Circuit (Choke) only functions near idle.

    It sounds like a clogged jet problem but I am guessing it is the Idle Jet.

    If with the Choke ON, and you advance the throttle briskly to a high RPM and it initially sputters coming through the mid-range and then roars to life, the MAIN Jet is clear.

     

    In any event, the solution is the same, the cleaning of the carburetor is in order.

    Next time, be sure to flush out the fuel hoses before you hook them up.

    just because they are New, doesn't mean they are clean.

    Running the Electric AUX Fuel pump for a minute with the hoses disconnected would flush the lines.

     

     


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


    Thank you said by: David HEAL

  • Re: Problem after Fuel line change

    by » 10 months ago


         Well, that sucks. I really appreciate y’all’s help.  Thanks again. -John


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