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912UL Runnability issues

in 912 / 914 Technical Questions 10 years ago

  • Re: 912UL Runnability issues

    by » 10 years ago

    Guys- thanks for all the suggestions, however it turns out its not fuel but spark. I have done a DCDI check and never had a issue before, but as I was syncing the carbs I had side "A"(top module) die on me. Hopefully I found my original problem- fingers crossed. I switched the red leads off the generator coils and the "A" side is still dead- so I switched DCDI's and it switched sides so I figured I had a bad DCDI. Ordered the soft start update(make sure you get the connectors and terminals as they don't come with the kit)and I still have a dead "A" side. Is it possible I have the trigger coils backwards? None of the schematics I have found match my wire colors, my trigger coil wires are white/red and white/green and the schematics say they should be white/yellow and blue yellow.
      
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  • Re: 912UL Runnability issues

    by » 10 years ago

    Let me answer my own question- yes it is possible to mix up the trigger coil wires, and yes they have to go a certain way or your Rotax will not run. Swapped pins around the right way- and viola- all is right with the world. Its pouring down rain outside so it will be a few days until I get back out to the airport but hopefully my problem is cured.

    Scott
      
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  • Re: 912UL Runnability issues

    by » 10 years ago

    So fixed all the electrical, both sides within 50 rpm drop- original problem of rough running still present. Checked all wires with a inductive timing light, pulled all caps and ohmed them out, new plugs with gaps verified, pulled valve covers and verified valves are all opening and closing, compression check ok, leakdown ok, carbs have been rebuilt 4 times, sync right on, gearbox is brand new, fresh out of ideas. Still runs rough below 2500 rpm. Total of 158 hours. If I never needed to land there would be no problem :woohoo:

    Who can I pull and send the engine to- I am about to that point.
      
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  • Re: 912UL Runnability issues

    by » 10 years ago

    It could easily be engine mounts or out of balance prop.

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

      
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  • Re: 912UL Runnability issues

    by » 10 years ago

    Roger- If the prop was out of balance would it not be rough running on top as well? It is a warp drive prop, which I am told is very heavy for the engine, but I swapped it out a while ago and it did not seem to help. Engine mounts are new.
      
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