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engine stumble at WOT

in 912 / 914 Technical Questions 7 years ago

  • Re: engine stumble at WOT

    by » 7 years ago

    Wrap your exhaust pipes and make sure all fuel hoses are in fire sleeve. If you're cooking a red Teflon hose line it could be put in fire sleeve to help insulate it. The header wrap Mfg's claim up to a 70% reduction in heat. Even if it's only 50% that's a lot of heat that isn't radiated or convected to wires and hoses.

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

      
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  • Re: engine stumble at WOT

    by » 7 years ago

    They are the red teflon hoses

    But the left feels significantly hotter than the right. I need to get a temperature sensor on it.

    Ok I'll get some fire sleeve and I'll also get exhaust wrap.
      
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  • Re: engine stumble at WOT

    by » 7 years ago

    Be sure to cover ALL the fuel lines in the Fire Sleeve.
    The Fuel pump is at the front of the engine.
    This means that the Fuel lines have to pass over the hot parts twice to get to the Carbs.
    Cover the hoses going TO and FROM the Fuel pump.

    HINT: AN6 Fire Sleeve can be found on eBay for under $5 a foot.
    - - - - -

    This is a great example of the difficulties of remote troubleshooting.
    Thermal issues are not something I am thinking about as I sit in Ohio.
    The Temperature is the upper 50's, a little chilly, and we are trying to stay warm.
    If I was standing there, the blistering heat would have been obvious.

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

      
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  • Re: engine stumble at WOT

    by » 7 years ago

    I got a chance to do some due dilligence / investigation on this issue last couple of days. I kept coming back to Air/Vacuum, fuel, spark and wanted to methodically go through and test.

    I removed and re-installed the left side inlet manifold (checking for gaskets, the seal and torque), I also took off the carb throat seal and the drips trays, cleaned that all up and re-installed. I checked the engine after that and saw the same stumbling at WOT.

    Next I wanted to see if the issue was to do with the main jet or the components of the main circuit on the left side. I took the float bowls off and swapped the main jets between the carbs, additionally I unscrewed the jet that is screwed into the bottom of the carb bowl (in the parts manual its just called "jet"), I blew it out and then blew out its seat, I could have sworn I saw something black fly out...

    I reassembled everything and tested the engine, NO issue and I sat there for a 5 mins on my timer at WOT.

    yesterday I got a chance to do some additional tests it was 101F outside, I performed a ground test after engine warmed up and tested for 5 mins at WOT, NO issue. I went to a wide open area of the ramp and tested a fast taxi, interestingly my RPMs rose about 150-200 from my static WOT. That is exactly what people see the RV12 do, but I have never seen on mine..
    Thank you said by: Sam Purpura
      
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  • Re: engine stumble at WOT

    by » 7 years ago

    Good Deal!

    Your diligence found the issue.
    As you now know, Just because you just cleaned the carbs does not mean they are clean.

    Happy to hear you are flying with confidence!

    Bill

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

      
    Report
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