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  • Re: Hard starting Rotax 912 ULS

    by » 11 months ago


    I'm with Sean. It sounds like it needs a new sprag clutch.


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


  • Re: Hard starting Rotax 912 ULS

    by » 11 months ago


    Now that your battery is good you’re going to need a new sprag clutch because of the week cranking previously or the propeller was turned backwards. The spring that holds down the little dogs has stretched and it’s not grabbing anymore.


  • Re: Hard starting Rotax 912 ULS

    by » 4 months ago


    So after it working/not working back and forth for months we finally came to the conclusion that is was the sprag clutch. I decided to have the local flight school do the work being a)they had the tools and b)had just done it on one of their planes. Unfortunately, they have some staffing issues and a couple months went by and they were not able to do it. So they offered to loan the tools to my A&P and I and we did the job ourselves. A bit of a PITA but we were able to replace it and all seemed good. I did 3+ hours of local flying with no issues. Of course last week I go to fly to NJ and lose my electrical system, which at the moment, does not appear related to the work we did. I do have to say the engine starts way better than ever with the new clutch.


  • Re: Hard starting Rotax 912 ULS

    by » 4 months ago


    Hello all

    In reading all the call outs on how to speculate on a sprag there is really only one effective test.   Go and download the correct SB for a start.  You will need a DC Amp clamp meter to read the draw on the starter motor.  If it is less than 75 amps your sprag is slipping, simple test.  

    Download the certified bulletin to get the details of the test and a lot of other suggestions.

    SB-912-042 R1

    Cheers

    37865_2_test for sprag electrical draw in amps.jpg (You do not have access to download this file.)
    37865_2_slip test DC meter .jpg (You do not have access to download this file.)

  • Re: Hard starting Rotax 912 ULS

    by » 4 months ago


    Sorry, the notation I added says "volt" meter, we need to read amps. 

    Cheers


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