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Wondering if anyone has any ideas as to why my 912iS would suddenly be creating tons of white grayish exhaust soot all over the length of the belly? The belly used to be super clean and exhaust never stuck to it. But now I get this nasty white grayish exhaust soot all along the belly all the way from the exhaust pipe to the tail covering half the width of the fuselage, and it only comes off with strong bug & tar remover. I exclusively use 100LL and have my entire ownership, so fuel hasn’t changed. Could this indicate some kind of a combustion problem that wouldn’t flag anything on the engine computer? 
  • Re: Rotax exhaust white grayish soot?

    by » 6 weeks ago


    Sounds like lead residue from the 100LL. 


  • Re: Rotax exhaust white grayish soot?

    by » 6 weeks ago


    Disregard. Created a new topic since soot is different color.

     

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    I have a copper colored soot clinging to the underbelly of my aircraft. It is about the color of rust water. It begins a few inches back from the exhaust and widens as it reaches all the way to the stabilator.

    Rotax 912iS that has exclusively consumed 91 octane unleaded mogas. The copper soot accumulated from the very beginning of usage and still accumulates at the same rate after 335 hours. Any thoughts on what could produce a soot of this color?


  • Re: Rotax exhaust white grayish soot?

    by » 5 weeks ago


    Oil vapors from the oil tank vent tube can cause this. Same color and I see it all the time. I use a product called "Oil Eater". It is water based and biodegradable and won't harm any type of aircraft skin and I wipes any oily or greasy residue off right off really easy.. It doesn't have all the harsh solvents in it like some fluids have.


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


    Thank you said by: Jayson Gieringer

  • Re: Rotax exhaust white grayish soot?

    by » 5 weeks ago


    Roger Lee wrote:

    Oil vapors from the oil tank vent tube can cause this. Same color and I see it all the time. I use a product called "Oil Eater". It is water based and biodegradable and won't harm any type of aircraft skin and I wipes any oily or greasy residue off right off really easy.. It doesn't have all the harsh solvents in it like some fluids have.

    For the grayish white soot or the rust/copper soot?


  • Re: Rotax exhaust white grayish soot?

    by » 5 weeks ago


    Copper colored. Greyish is usually exhaust. I see the grey all the time around the exhaust knuckles where they meet the muffler from leaks. If it was a big leak then that can be blown out to the bottom of the plane. I'd start by looking at my exhaust / muffler knuckles for leaks since it's a common occurrence. 


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


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