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Carb issues

in General Tech Discussion 10 years ago
Last year I rebuilt the carbs on my 912UL. To get it to develop full power, I had to lower the circlips to the third notch down. It runs fine in warm weather however in colder weather it seems like the carbs ice up. If I land and shut off the engine for a few minutes, it will have good power again for a while. Do I need to lower the circlips to the bottom notch?

  • Re: Carb issues

    by » 10 years ago

    Hi jerry,
    First you should install a carb heat system!
    Rob
      
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  • Re: Carb issues

    by » 10 years ago

    Rob:
    I have not needed a carb heat system before and this happens on low humidity dry days.
      
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  • Re: Carb issues

    by » 10 years ago

    Strange, it sure sounds like carb ice.
    Try going to the 2nd notch, the bottom notch is extreme and seldom used.
      
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  • Re: Carb issues

    by » 10 years ago

    The clips on the needle on the 912ULS should be in the third notch and come that way from the factory.
    Just a couple of questions to help trouble shoot.

    Did someone alter the original clip position and move them to the second notch?
    Lowering the clip from #3 to #4 position will make them quite rich. What kind of outside air temps and humidity are you dealing with where you live?

    Is this an open air engine or in a tight cowl? Are you using cooler outside air from an air intake duct or do you have the air filters attached directly to the carbs?

    Are we sure it is icing and not floating debris inside the carb?

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

      
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  • Re: Carb issues

    by » 10 years ago

    Thanks for your input, guys. This is the 80 HP 912UL in a Kitfox3. The air filters are not connected directly to the carbs. They have short Scat hoses and are fastened to the oil tank far back in the cowling. Before I overhauled the carbs, the circlips were always in the second notch from the top. After overhauling the carbs, I couldn't get any power out of the engine until I moved them down to the 3rd notch. The fuel nozzles were replaced on the overhaul. When the air temps are 70 or higher, it runs fine, If it's below 50 and I back off the power, the engine doesn't want to come up to speed again. If I land and shut it off for 10 minutes, it will have good power again for a while. I'm sure the fuel bowls are clean. I'm not sure it's icing, but it kind of acts like that.
      
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