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Vibrations 2000-3000 RPM on final

in 912 / 914 Technical Questions 5 years ago
Hello,

Probably an old item. On final vibrations between 2000-3000 RPM but not on the ground. Too rich? Install a 0.30 idle jet?

Thanks.

Jan

  • Re: Vibrations 2000-3000 RPM on final

    by » 5 years ago

    Check that the piston under the diaphragm moves easily and down. I had the same thing happen and I just cleaned and re lubricated the internal bronze bushing that keeps it centered.
      
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  • Re: Vibrations 2000-3000 RPM on final

    by » 5 years ago

    What Engine?
    What Gearbox?
    Clutch?

    There is a middle ground where during part of the rotation cycle the Propeller outruns the Crankshaft and on the next Power stroke the crankshaft catches up. Slack-Bump-Slack-Bump...
    At High power, the prop slows down fast enough that no slack occurs.
    At Low power, the forces are so low as to be unnoticed.
    It is only in the middle power settings that the prop and crankshaft get into a fight.
    On the ground, the prop is always pushing air.
    During the glide on final, the prop becomes unloaded due to the relative wind.

    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    Clicking the "Thank You" is Always Appreciated by Everyone.

      
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  • Re: Vibrations 2000-3000 RPM on final

    by » 5 years ago

    I also have a sync problem at 3000 rpm
    How do you clean and lubricate?
    What oil do you use?
    Thank you
    Jacques
      
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  • Re: Vibrations 2000-3000 RPM on final

    by » 5 years ago

    I wanted to talk about the piston above the diagphram, and Garrett's solution
      
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  • Re: Vibrations 2000-3000 RPM on final

    by » 5 years ago

    My problem started after Lockwood installed a new fuel pump after a gear box service/inspection. Initially the new pump was over pressurizing and caused the carburetors to flood and then the engine would vibrate and shake after the power was pulled back on final. I called Joe at Lockwood, described the problem and he immediately suggested check the slides, he said that the flooding washed away any lube and the blue dye left over from the 100LL would cause the slides to stick unevenly causing an out of sync condition. I cleaned the bronze slider bushing with mineral spirits and then re lubed with engine oil. The engine ran better than it had in a while as I think the carbs were staying perfectly synced with the sliders moving freely because of fresh lubricating oil. If you take the diaphragm and top of carb off make sure when reinstalling to put the alignment tab on the diaphragm back in the proper position so the slider is properly aligned.
      
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