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Thread: Rotax 912 running rough all of a sudden?

  1. #1
    Senior Member Peteohms's Avatar
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    Sep 2008
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    Leander, TX Hangared @ KGTU
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    Default Rotax 912 running rough all of a sudden?

    Engine has been running great. Flew last weekend and then Wednesday was going to fly. Started up and it was sounding rough at idle. I warmed up a minute and advanced the throttle and it continued rough until it got to 3000 rpm. Let it warm up some more then ran it at 3000 rpm for a couple minutes hoping to clear up the problem. No joy. I ran it at high idle and turned off the fuel valve. After a while it smoothed out just before it was starved for fuel. Opened the fuel valve before it died and it ran smoothly for a few seconds before it began to run rough again. Sounds like a carb problem where maybe one carb is getting too much fuel. Mag check at 3k is normal. I dropped the float bowels and the floats looked to be floating normally. Fuel looked clean. I had run on this tank for a couple hours Saturday. Gascolator had clean fuel. Suggestions? Why would a good,running engine start running rough after just a few days?
    Pete
    Leander, TX
    Model III SN 1000
    912
    Grove

  2. #2
    Senior Member kmach's Avatar
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    Nov 2009
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    Cupar, SK, Canada CLC4 Loon Creek Airfield
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    Default Re: Rotax 912 running rough all of a sudden?

    Are the starter carb cables and return springs allowing the arms to fully return to the off position?
    Any debris in the carb bowls or in the float needle valves?

    Some things that came to mind.
    Kevin,

    Kitfox Outback
    912 ULS
    Airmaster AP332CTFH-WWR70W
    Summit Aircraft Wheel Skis
    C-FOXW

  3. #3
    Super Moderator Av8r3400's Avatar
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    Merrill, WI
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    Default Re: Rotax 912 running rough all of a sudden?

    Pull off the bowls and weigh the floats. Sounds like a float went heavy...
    Av8r3400
    Kitfox Model IV
    The Mangy Fox
    912UL 105hp Zipper
    YouTube Videos

  4. #4

    Join Date
    Jun 2013
    Location
    Spokane, Wa
    Posts
    120

    Default Re: Rotax 912 running rough all of a sudden?

    Check your intake manifolds as well, could be torn.

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