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Thread: older 912 ul heating up

  1. #21

    Join Date
    Jan 2011
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    Default Re: older 912 ul heating up

    Ok guys here is the update have about 20 hours on the old bird have 168 main jets in carb EGTs at 1550 F at max, coolant temp at 230 F max , cylinder head temp 260 F runs great. Still not sure why I had to open up jets to get to right temps?? Here are some pic of the plugs, one from each side what do you guys think of color of plugs . Still looking for cause
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  2. #22
    Senior Member jiott's Avatar
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    Default Re: older 912 ul heating up

    Color looks about right to me; if anything maybe a tad on the hot (lean) side.
    Jim Ott
    Portland, OR
    Kitfox SS7 flying
    Rotax 912ULS

  3. #23
    Senior Member jiott's Avatar
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    Default Re: older 912 ul heating up

    I don't see any sign of the white thermal paste you should be using. Definitely use it, it will cool the plugs somewhat.
    Jim Ott
    Portland, OR
    Kitfox SS7 flying
    Rotax 912ULS

  4. #24
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    Default Re: older 912 ul heating up

    I think the color is darn near perfect. The gaps seem to be a little different but that may just be the different photo angles. I do agree that the larger jetting is compensating for a different carb problem. Such as incorrect fuel float level and/or sinking floats.

  5. #25

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    Default Re: older 912 ul heating up

    The carbs are brand new ?? But I will check height of floats and adjust to the heavy side and see if I can get to run rich. thanks for the help guys love flying this plane.

  6. #26
    Super Moderator Av8r3400's Avatar
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    Default Re: older 912 ul heating up

    Just because they are new doesn't mean they don't have bad or badly adjusted floats in them. There have been several series of bad floats coming out of Rotax (Bing) in recent years.

    I agree with Danzer1, those jets are unnecessarily huge and masking a different problem. What about the rubber boots between the manifolds and carbs? What about the o-rings on the intake manifold to head seam?
    Av8r3400
    Kitfox Model IV
    The Mangy Fox
    912UL 105hp Zipper
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  7. #27
    Senior Member Dusty's Avatar
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    Dec 2012
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    Default Re: older 912 ul heating up

    It has been suggested before, but have you checked your vent lines.
    These make a huge difference.if they are vented into the K&N type filters like mine you will need to be up a jet size or two.

  8. #28
    Senior Member jiott's Avatar
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    Default Re: older 912 ul heating up

    Mine are vented into the K&N filters and needed no jet change from the standard.
    Jim Ott
    Portland, OR
    Kitfox SS7 flying
    Rotax 912ULS

  9. #29
    Senior Member jrevens's Avatar
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    Default Re: older 912 ul heating up

    Same here.
    John Evens
    Arvada, CO
    Kitfox SS7 N27JE
    EAA Lifetime
    Chap. 43 honorary Lifetime

  10. #30

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    Default Re: older 912 ul heating up

    I need to check the float height but seems to me if floats were low you would run out of gas at WOT on take off I have replaced all the rubber O rings and carb flange boots and ran motor spray down intake manifolds looking for leaks it is good but I’m not giving up . Guys have a great 4th holiday

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