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I've read through many posts and responses and I believe that the low-rpm engine roughness that we are experiencing is due to a gearbox issue (which I believe is near or over the inspection time anyways).  The carbs are synced, the plugs are good, and the mounts are in good shape and torqued.  In looking at the manual I see no reference to a "belleville" washer which is mentioned many times in the forums.  I assume the washer between the dog gears which the book seems to call 2 different things is the "compression disc/plastic thrust washer" but please correct me if I am wrong.  I appreciate any help or information and thanks for all the posts you all make, it has been very helpful. 

  • Re: Engine roughness at low idle

    by » one month ago


    The 'belleville washers '  are called 'disc spring' in the parts manual.

    There are 2 or 3..depending if there is a clucth or not

    in yellow in the attached drawing

     

    https://en.wikipedia.org/wiki/Belleville_washer

     

    30883_2_912 gearbox parts.JPG (You do not have access to download this file.)

  • Re: Engine roughness at low idle

    by » one month ago


    The large metal bellville washers or compression disc if you like are down low in the gearbox. You most likely have 3 of them unless you have a 912UL and or older engine. The plastic thrust washer is up under the top small gear. Over time the bellville disc can loose tension and or the thrust washer could get damaged. The latter is fairly rare. These both get replaced during a gearbox inspection. If the vibration in the gearbox has gone on long enough or has been severe enough you can damage the gearsets and may need replacement during the inspection. Idling at too low an rpm, carbs way out of balance or a prop way out of balance will add and accelerate gearbox wear / damage.


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


  • Re: Engine roughness at low idle

    by » one month ago


    What are the results of your latest friction-torque test?


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