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Hello, 

I have a 912UL with a edge performance 100 HP upgrade. The A&P that installed the kit was at 1300’ elevation. He installed 165 main jets and 2.74 needle jets. I am at 6200’ elevation and I am fouling plugs with black soot. I found the needle jet clips on the richest setting, I moved them up to the second from the top. This helped but I still have soot. Can you help me with the proper jet sizes for my elevation?

thank you

  • Re: 912 UL jetting

    by » 2 weeks ago


    Have you been idling before checking plugs? It can be normal to get dry black spot on plugs in idle rpms. What are the plugs gapped at? That burns off at higher cruise rpms. 


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


  • Re: 912 UL jetting

    by » 2 weeks ago


    My plugs are gapped at .031. The spark plugs were checked after a run up to 4000 RPM to check mag drop.


  • Re: 912 UL jetting

    by » 2 weeks ago


    Reduce the plug gap to .025 gap. Unscrew each plug wire to the plug rubber boot and trim each wire back 3/8", apply a dab of dielectric grease to the end of each plug wire and screw them back on until they are fully seated. Now repeat your test. 

    Mag drop test time isn't long enough. It needs to run at those higher rpms much longer.


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


  • Re: 912 UL jetting

    by » 2 weeks ago


    Thank you. 
    I am assuming then that my jetting is ok for my elevation? I will reduce gap and reply with results.

    thanks


  • Re: 912 UL jetting

    by » 2 weeks ago


    Use your EGT's to help for carb adjustment. This should be more aimed at high rpm settings like cruise and climb. Make sure the mixture screw on the bottom of the carb is adjusted properly.  Make sure carbs are synced.

    I never check the plug real burn at idle circuit rpms.


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


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