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912S back firing problems + ignition timing

in 912 / 914 Technical Questions 12 years ago

  • Re: 912S back firing problems + ignition timing

    by » 11 years ago

    Bill,

    Are the kickbacks caused by a faulty sprag clutch can damage the crankshaft or other parts and resulting in an in-flight engine out?

    I experienced rough kickbacks on start-up. I already had the HD starter and SSM module. I put a new battery and a charger unit that keeps the battery always full charge. I discovered that my engine starts better and make a lot less kickback if I crank it for a couple of revolution and then turn on a magneto. The inertia of the prop helps the engine not to kickback.

    Thanks,

    Pat
      
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  • Re: 912S back firing problems + ignition timing

    by » 11 years ago

    As the starer spins up the sprag is engaged and as the engine starts it over speeds the starter and the sprag releases. If you have a bad sprag it usually causes hard starts and a poor engagement of the sprag.

    All of what Gregoire said will help a start up and keep kickbacks away. Using a light composite prop compared to a long and or nickel edge heavy Warp Drive prop will also help stave off kickbacks. They can also be a result of low gearbox slipper clutch pressure and poor carb setup, sync and throttle position at start up.

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

      
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  • Re: 912S back firing problems + ignition timing

    by » 11 years ago

    Also check the earth connection on the engine.
    I had a problem on my SoptCruiser.
    The connection looked to seem in very good condition but after disassembling cleaning up and re assembling
    the engine started a lot better.
    Later after installing the soft start system from Rotax, the engine start very smooth now

    Best regards,
    Guy
      
    Report

  • Re: 912S back firing problems + ignition timing

    by » 11 years ago

    I have the same problem with sprag clutch after 300h. Rotax have made some changes of engeene since 2007, new flywheel, stronger spiral-spring in sprag cluch, soft start module and suggest not to have long startcabel.
    Now I make new fiywheel and sprag clutch, soft start modul is mount 2 years ago, but I am a little unhappy about rotax and not thinking it is my fault, I have made a super instalation in the plane and made all handling of engene by my self.
      
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