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While inspecting my carbs (for a 912 ULS), I noticed that the piston on the 1/3 carb creates a larger opening in the throat than the one for the 2/4 carb.  Both pistons have the same markings, but significantly different geometry.  As far as I can tell, there's just one part number for the carb pistons.  Can someone explain why they might have different sized "apertures"?  Photo attached – 1/3 carb is on the left.

8656_1_carb pistons.jpg (You do not have access to download this file.)
  • Re: carb piston "apertures"

    by » 12 months ago


    yep. You have a problem. They should both be down flush with the piston base where it curves. I've only seen this a few times.


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


  • Re: carb piston "apertures"

    by » 12 months ago


    Well, just my luck! 

    Roger, are you saying they both look wrong, or just one?  

    What was the solution the other times you saw this? Just replace the piston(s)?


  • Re: carb piston "apertures"

    by » 12 months ago


    We have never come across this before. It looks like one of the piston slides was machined wrong or is from a different BING Carburetor. Here is a photo of what they normally look like and a rough dimension with a caliper to show you the proper size. 

     

    Please click on this link and submit a CSIR  https://rotaxirmt.com/registration/sir#step-1

     

    29730_2_20210607_103210.jpg (You do not have access to download this file.)
    29730_2_20210607_103233.jpg (You do not have access to download this file.)

    Thank you said by: Tyler Hathaway

  • Re: carb piston "apertures"

    by » 12 months ago


    I have seen a similar issue on a bing 54.

    I can only assume that as these carbs are also used on ground application engines, there are slight differences.....perhaps a slide from a BMW motorbike has found its way into your carb.


  • Re: carb piston "apertures"

    by » 12 months ago


    I've seen it and just press fitted it back down in place and they have always stayed.


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


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