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912UL Engine vibration on throttle back

in 912 / 914 Technical Questions 12 years ago

  • Re: 912UL Engine vibration on throttle back

    by » 6 years ago

    Attending those Rotax Maintenance classes is a great thing to do. And the best thing you learn there (if you are smart) is where to send your engine or parts thereof for repair. Unless you are doing maintenance on a regular basis in ma competitive scale you will never remember half of what you saw at school. I highly recommend every Rotax owner attend all three classes if at all possible. Been to all of them at South MS Light Aircraft. Wonderful people there. Well worth the time and small cost.
      
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  • Re: 912UL Engine vibration on throttle back

    by » 6 years ago

    This is a well known syndrome to many 80 h.p 812 owner/users.
    Failure from excess wear at the gearbox sliding splined output shaft and its splined drive cam.

    My first lasted 700 hours, the second installed last year only 47 (yes, 47 hours) then vibration on the over-run was horrible. A new splined pair from Rotax UK agent cured it, but theyv'e now modded the design to include and oil way to spline plus the inside feeder oilways. (not readily retro-fitted).

    So nothing you can do, prop, engine, mounts, carbs all O.K. but suspect meatl and/or its correct heat treatment and hardness at this spline mean Rotax have at best a marginal design, or as I fear, lower standard application to new cheaper sub-suppliers. See the LAA magazine October 2018 for photo and article.

    mike hallam, UK
      
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  • Re: 912UL Engine vibration on throttle back

    by » 6 years ago

    Thanks Roger,
    well said. We have about 150 Rotax engines on the field and many reach TBO easily, and many do not.

    The common factor to the ones that do not is people not doing regular maintenance, people thinking they know more than Rotax and people using them wrong because the "just know" that they are right.

    They are the best engines out there, just use them exactly as Rotax says, do the maintenance with a well qualified Rotax engineer whom does many engines, and 95% of the problems will go away.

    Regards

    Glenn
      
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  • Re: 912UL Engine vibration on throttle back

    by » 6 years ago

    Hi Glenn,

    New Zealand. Just a hop, step and jump across the pond. I'll be there for lunch. :)

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

      
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  • Re: 912UL Engine vibration on throttle back

    by » 6 years ago

    Rotax definitely has a gear problem in several of their later 912 series engines. Not sure what they are doing about it but it is becoming widely known now. I am one of the lucky winners of a set of their bad gears. Drove me crazy for the last three years. Couldn’t believe Rotax had put out anything that wasn’t first class.
      
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