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I recently purchased a plane with a 80hp 912. After about 8hrs of flying it started to miss, I advanced the throttle to climb and it was better but still noticeable. Once at a safe altitude I reduced the power to idle for 10 seconds or so then went back to cruise rpm(4900). After this it ran perfect, once back over my home airport I did some turns and a descent and it had the miss again. I reduced power to idle and it was good?

I did some searches on and thought it would be best to rebuild the carburetors. I rebuilt them and replaced the floats with new. The first flight after that I had the same issue and after going to idle I didn't have it the rest of the day(2.5 flying hrs)? I have checked for water and sumped the fuel system and did not find any signs of water in the fuel.

I have already replace the plugs, voltage regulator and done a oil change before any of this. The engine currently has 550hrs.

Any ideas?

  • Re: 1995 912UL miss

    by » one month ago


    The intermittent miss can be tough to solve so assume nothing and check everything from a vacuum leak to plug wires or carb balance issue.


  • Re: 1995 912UL miss

    by » one month ago


    Just a question or two.

    You need to try an narrow down whether it is electrical or fuel related. 

    What is the mag check and is it reasonably equal? How about checking the carb sync? The gauges may reveal an issue. (Not with an electronic carb sync tool) Re-checked the carb bowls for debris? Some of your comments could point to debris.


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


  • Re: 1995 912UL miss

    by » one month ago


    When I went thru the carburetors there where really no loose debris. The right side mag check at 3000 rpm drops more than the left and feels like the engine is rougher, if that is a thing? To be honest I have not checked the carb sync. The darn thing idles and runs so smooth I didn't take the time but I can.

    Really weird to me why the idling for 5-10 seconds fixes it. I really thought I had water in the fuel somewhere initially.


  • Re: 1995 912UL miss

    by » one month ago


    If it has always been fine before the plug change, could it be a problem with the new plugs? Are any of them loose? Could there be a problem with one of the plug leads? Either the resistive end cap or where it screws into the lead.

    When you get the fault can you switch to one ignition and see if that makes it better?


  • Re: 1995 912UL miss

    by » one month ago


    I torqued all of the plugs and double checked them but anything is possible. The fact that it is intermittent is the hard part. We flew over a hour and a half on the way home Saturday with no problems.


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