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Really need help here with my 80hp.  During this morning’s oil sump vent/gurgle, after counting 23 compression cycles, the oil tank gurgled.  Then I turned the prop to get one more gurgle and the prop kicked like it was going to start hitting the back of my hand.  ALWAYS TREAT A PROP AS IF IT WERE HOT!   But the question is how could it do this?  Do 912s do this?  Hand blue and hurting, I started the engine and did about 50 mag checks.  Each individually toggle switch throw dropped the RPM about 175 + - nothing (0) differnce between one and the other.  And the engine shut down with the switches as it should, but I did hear one backfire as it stopped.  What caused the prop to fire?  Is this normal?  Is it something I can fix?  I run 100% mogas with ethanol but previous owners had run 100LL.  I replaced the plugs 30 hours ago.  The engine had not been run in over 24 hours, so it was stone cold.    In my 230 hours with a Rotax 912, I have never had the prop kick during hand rotation.  I didn’t think our engines could be hand-propped to fire?  HELP!

  • Re: Prop fired during sump/tank gurgle

    by » 4 months ago


    Dennis, any updates? Looking through the Rotax manuals, what I’ve found is there should be no spark from either ignition module below 90 engine rpm, and the ignition must provide spark at a minimum of 150 rpm, so unless one can hand prop about as fast the starter motor, there should be no spark to the plugs.

    Jim

    Dennis, no it should not behave like that, nor should it backfire.  Have you called Lockwood, Ronnie Smith at South MS Light Aircraft, or Rotech Canada and asked for tech support help?

    Jim


  • Re: Prop fired during sump/tank gurgle

    by » one month ago


    Well, I just watched a video on YouTube of a man hand propping his aircraft and although the engine is not visible (cowlings in place) he states in the video the engine is a Rotax 912, and the purpose of his video was to determine if it could be done. He was able to start the engine.


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