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Rough Running.......need help.

in 912 / 914 Technical Questions 10 years ago

  • Re: Rough Running.......need help.

    by » 10 years ago

    Travis,

    Roughness is not normal, mine was smooth until 20 hours ago.

    Mine there is no noise from engine like misfire, outside plane it is not possible to tell there is problem, only rough running felt through airframe inside.

    I have checked all rubber motor mounts. Mine has 2 piece rubber and metal spacer in middle with 2 large metal washers at ends. I just torque down bolt so washers contact spacer. Motor mount frame does not touch spacer, rubber is in way.

    If I cannot borrow carbs from 912 motor I am planning to buy some Bing 64/32 from BMW motorcycle from eBay. These look almost same but much less cost. I will change jets to same as 912 carb. They will let me find fault so I can then buy correct part for 912 carbs.

    Grzeg
      
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  • Re: Rough Running.......need help.

    by » 10 years ago

    His engine may be running smooth and the vibration being generated from something else.
    Engine mounts should always at least be suspect and has caused vibrations in quite a few aircraft until ferreted out.

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

      
    Report

  • Re: Rough Running.......need help.

    by » 10 years ago

    Yesterday I try another pair of carbs that someone lended me. My rough running problem is still same after balance carbs. I also check ignition timing with strobe and it measures 26 degree before and stable.

    My next step needs motor to be taken apart and look inside.

    Not happy :(
      
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  • Re: Rough Running.......need help.

    by » 10 years ago

    If I missed this in an above post just disregard.

    Have you done a differential compression test?

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

      
    Report

  • Re: Rough Running.......need help.

    by » 10 years ago

    Yes, differential pressure test has 1% leakage on every cylinder. Standard compression test has > 6bar on every cylinder.

    I think valves and pistons are good.
      
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