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Sudden Onset Extreme Rough Running on Rotax 912

in 912 / 914 Technical Questions 8 years ago

  • Re: Sudden Onset Extreme Rough Running on Rotax 912

    by » 8 years ago

    Thanks for the gold star, I'll use the gold to offset the falling value of our British pound ;-)

    Here are my thoughts on the lack of valve movement:
    1. Broken rocker
    2. Broken head casting (not supporting the rocker fulcrum)
    3. Broken pushrod
    4. Broken/missing tappet
    5. Broken camshaft lobe


    Most of these you can inspect with just the rocker cover off. The last few will require the head to be removed, just follow the procedure in the heavy maintenance manual. It shouldn't take you too long, just drain the coolant, remove the coolant hoses, inlet manifold, exhaust, etc. Be careful when you remove the head, it will have some oil in it as will the pushrod tubes. Don't let the pushrods drop out of the tubes, keep it all horizontal and place it all in a bowl/tray. Do not lose the large pushrod tube O rings and be careful when reassembling to make sure that they don't get caught otherwise you'll have a serious oil leak.

    If you want to remove the tappet use a magnet and gently slide it out. You should then be able to inspect the camshaft. I don't know what happens if you rotate the crank with the head off. You will have to be careful as there will not be anything holding the cylinder to the block. Also I don't know if any oil will be forced out of the pushrod holes.

    Kevin
      
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  • Re: Sudden Onset Extreme Rough Running on Rotax 912

    by » 8 years ago

    I've just spoken to someone more knowledgeable about these things than me and this was the advice:

    If the pushrod is not moving then smell the oil in the tank, if it smells like burnt steel like in a machine shop then the outcome is not going to be good. It probably means that the cam has gone and you have metal paste travelling around the engine damaging everything in its path :-(

    Let's hope that this is not the case.

    Kevin
      
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  • Re: Sudden Onset Extreme Rough Running on Rotax 912

    by » 8 years ago

    Here's a more likely scenario.

    This is more likely the loss of the hardened metal coating on a lifter. It is a poor metallurgy issue. If the metal hardness coating fails the crank grinds the lifter down. This might happen 1-2 times a year. If this is the case the magnetic plug will be coated with metal fuzz and look like it has a beard. If you run the oil in the tank over a couple of magnets when it drains it will have metal on them. If you cut the filter open and wash the filter in gas and then pour that mixture through a white paper towel it will have metal fuzz in it. If you remove the head of that cylinder and just slide the cylinder back just enough the tappet s should just slide out. If one is stuck in place you have your answer. Do not force it out and it probably won't come out because the other side of the tappet has been ground down and flattened. This means the tappet is gone and so is the crankshaft. The metal filings are throughout the engine and seals.

    The engine is done and not reusable.

    If this has happened you NEED to fill out a CSIR, copy your entire engine logbook, a brief description of what happened and send it to your regional service center. If you have kept good detailed logbooks and followed the Rotax preventive maint. recommended along the way then Rotax may offer you some help with a new engine. This is just one reason I have preached and preached about good record keeping. If you have poor records and poor maint. practices then you may be on your own.

    I know exactly what this is like as it happened to me at 833 hrs. If this did happen then there is no warning and there was no way to prevent it unless you caused it by poor oil choices.

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

      
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  • Re: Sudden Onset Extreme Rough Running on Rotax 912

    by » 8 years ago

    As you both suggested, I removed the head of the cylinder with the intake valve that was not opening. The lifter for the exhaust valve came out easily, but I could not get out the one for the intake valve with either a magnet or several different styles of right angle picks. I then pulled the magnetic plug, and it was covered with metal fuzz (at all my 100-hr maintenance/inspections it has been clean).

    Thus what I found was pretty much exactly what Roger described in his scenario. I did not drain the oil over magnets or check the oil filter, but I have no doubt that there would be lots of metal bits showing up in those.

    So it looks like I'll be grounded for awhile, but at least now I know what happened.

    Roger - did Rotax ever come out with a bulletin or notice about this problem? I have seen ASB-912-051UL (Checking of Magnetic Plug) but it does appear to refer to anything like this particular failure mode (however my plug looked very much like the pictures shown there). My engine is likely a 2006 production model, since the production date on my trike was November, 2006, and its serial number is in those covered by that ASB. Did you have any luck getting Rotax to help with a new engine when it happened to you?

    I do have complete maintenance records on the engine, and have changed the oil (AeroShell Oil Sport Plus 4) and filter every 100 hours.

    Thanks to you both for helping me track down this problem (I only wish it had not been such a catastrophic failure!!!)

    Paul
      
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  • Re: Sudden Onset Extreme Rough Running on Rotax 912

    by » 8 years ago

    Hi Paul,

    The 2006-2007 is where I have seen these. I was told it only happens to 1-2 per year and is something that wouldn't dictate a special bulletin because it is so rare. The hardness coating (metallurgy) on the head of the lifter failed and the crank ground the lifter down. The engine now has fine metal dust throughout everything and isn't salvageable. There are however many good valuable parts still on the engine.

    Sorry. It happened to me also and my engine at the time was a 2006 with 833 hrs. That was a few years back.

    If you are in the US go here and under support docs: http://www.rotaxflyingclub.com/search/tech_doc
    and get the customer service information report. Do not leave ANY blanks empty. If it isn't applicable write that. Write a description of what happened and any anomalies noted at that specific instance. Copy all the pages out of your engine logbook from the begining. Contact your service center (for you it is CPS in CA) and let them know this is coming. Call them in a week or so and MAKE SURE they sent it into the Rotax Flying and Safety club group for processing. It may take a while, but follow up every week or so, so it doesn't get lost in the cracks. Rotax needs to know what's going on.

    Anyone that has a Rotax issue of any kind should be sending these reports in otherwise Rotax will never know.

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

      
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