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Rotax 912 ul, severe vibration

in 912 / 914 Technical Questions 8 years ago

  • Re: Rotax 912 ul, severe vibration

    by » 8 years ago

    Here is a mind map that I have done to help. I used Free Mind if you want to edit it.

    Roughrunning.jpeg (You do not have access to download this file.)
    Roughrunning.zip (You do not have access to download this file.)
    Thank you said by: Jorge, Dr William Scott
      
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  • Re: Rotax 912 ul, severe vibration

    by » 8 years ago

    Hi,

    yes, the 860990 covers are installed. I also tried running the engine at night looking for arcing but couldn't see any.

    No, I swap every single component of the ignition system, being systematic every time, cleaning contacts, making sure the wiring order was correct, etc. From the stator, to the ignition coils, CDI, ignition wires, spark plugs connectors and spark plugs (new).

    Because of all this and that the ignition test it's ok I kind of rule out the electrical origin of the diagnosis thinking that, as you said, it might be due to the cranking speed ... but that's just a supposition.

    Thanks for the mind map, I will be using it in the future. Question, what are the followers?

    I have done all that but doubting about the gearbox since no new parts were installed. I've been told by several repair shops that there is some parts to change at minimum when opening it for a control check. Still thinking that maybe the guys who inspected mine missed something.
      
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  • Re: Rotax 912 ul, severe vibration

    by » 8 years ago

    Do you tryed to change the propeller. I now propeller stored with one blade down, that blade are havyer! Even carbonfibre propeller in a dry hangar!/eyolf
      
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  • Re: Rotax 912 ul, severe vibration

    by » 8 years ago

    Jorge,

    The followers are the hydraulic lifters that go between the camshaft and the push rods. I am not sure how to test them other than to remove and inspect them.




    If you still suspect the gearbox then I would run the engine with the prop removed. You won't need to run it for long to know whether that is your problem. I know that others on this forum have reservations about this technique but it would give you a definitive answer.

    Kevin
    Followers.jpg (You do not have access to download this file.)
      
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  • Re: Rotax 912 ul, severe vibration

    by » 8 years ago

    Eyolf, I tried with a different prop and no change.

    I always paid special attention for any improvements when I tried something (on the electric, carbs, prop,etc). The shake is been always the same with no changes on sound, frequency, strength,etc.

    Followers, that's understood. I call them hydraulic tappets, I heard it from my engineer but I don't know if this is the proper english word. Those were inspected the first time the engine was dismantled and replaced with a new set the second time.
    Same, same ... :angry:

    I am out from home until October when I am planning to re-install the engine and take it step by step.

    I'm hoping to see some improvement with the shortened gasket on the engine mount rubbers and continue from there.

    If this evil machine keeps trying to blow up, then I will send the gear box for a proper inspection again. It will cost me "only" another 500 dollars ... after how much I spent in this engine it would be stupid no to try.

    An then If that doesn't work, and with great regrets, I have a buyer interested already!
      
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