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Thread: Carb flooding and venting, Kitfox4 912 UL

  1. #1

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    Default Carb flooding and venting, Kitfox4 912 UL

    After a 5 year rubber replacement, we started the engine to check for leaks and balance the carbs. In the course of the replacement, we had removed a fuel regulator which the previous owner had in the line to the carbs from the fuel pump. Checking with Lockwood Aviation, we had been told that was non standard and not needed to regulate fuel pressure. After starting, the engine ran well for several minutes. Then both carbs began venting and flooding. I consulted the previous owner as to why the fuel regulator was installed. His response was the the carbs had begun to vent and flood. So, he had installed the regulator to reduce the fuel pressure and stop the flooding and venting. The solution I have in mind is to replace the both carbs.

    I am wondering if anyone has encountered a similar situation, or would like to comment. Thanks.
    Bob

  2. #2
    Senior Member jiott's Avatar
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    Default Re: Carb flooding and venting, Kitfox4 912 UL

    Before replacing the carbs, I would suggest you replace the little rubber-tipped needles AND the seats in both carbs. Very likely they are worn and don't seal well at the normal fuel pressure.
    Jim Ott
    Portland, OR
    Kitfox SS7 flying
    Rotax 912ULS

  3. #3

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    Default Re: Carb flooding and venting, Kitfox4 912 UL

    I bought the 5 year Hose and Rubber Component list from Lockwood Aviation which included the fuel pump, float needles, diaphragm, Carburetor Overhaul Kit, etc. I think the seat might be at fault. Lockwood thought so too, with no guarantee that they could fix it. Rather than loose more time, I'm going to bite the bullet with new carbs. Toys that don't work are kind of useless. Thanks for your comment.
    Bob

  4. #4
    Senior Member rv9ralph's Avatar
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    Default Re: Carb flooding and venting, Kitfox4 912 UL

    Did you check the floats to ensure they do not sink. Rotax-Owner.com has the Service Bulletin detailing the process.

    Sinking floats will not close the needle valve that keeps the fuel bowl from overfilling and spewing fuel out the vent lines.

    Ralph

  5. #5
    Super Moderator desertdave's Avatar
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    Default Re: Carb flooding and venting, Kitfox4 912 UL

    That's what happened to mine. I pulled the carb bowls off and one of the four floats was sitting at the bottom of the bowl. Sounds like Bob wants to get back flying ASAP with ordering new carbs.
    Dave
    KitFox 6 Taildragger
    912 ULS
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    All around nice guy

  6. #6
    Super Moderator Av8r3400's Avatar
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    Default Re: Carb flooding and venting, Kitfox4 912 UL

    Did they supply the red or black needles? I believe the red ones are softer and work better with the reversed intake manifolds on a Kitfox 4.
    Av8r3400
    Kitfox Model IV
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  7. #7
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    Default Re: Carb flooding and venting, Kitfox4 912 UL

    If you want a deal on new carbs, Jason Busat from BadAss powersports sells new carbs with intake manifolds and fuel pump for $1250. I got a set from him and they are new. He strips these parts off new engines and puts fuel injection on the engines. Here is the stuff I got from him a couple of months ago. JImChuk

    PS a pair of floats should not weigh more then 7 grams together. I've seen them weigh as low as 2.8 grams each. I would verify this is not the problem. Also, do you have a return line? New style fuel pumps make more pressure than old style ones.
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    Default Re: Carb flooding and venting, Kitfox4 912 UL

    Quote Originally Posted by rv9ralph View Post
    Did you check the floats to ensure they do not sink. Rotax-Owner.com has the Service Bulletin detailing the process.

    Sinking floats will not close the needle valve that keeps the fuel bowl from overfilling and spewing fuel out the vent lines.

    Ralph
    The floats floated. Thanks for the comment.
    Bob

  9. #9

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    Default Re: Carb flooding and venting, Kitfox4 912 UL

    Quote Originally Posted by avidflyer View Post
    If you want a deal on new carbs, Jason Busat from BadAss powersports sells new carbs with intake manifolds and fuel pump for $1250. I got a set from him and they are new. He strips these parts off new engines and puts fuel injection on the engines. Here is the stuff I got from him a couple of months ago. JImChuk

    PS a pair of floats should not weigh more then 7 grams together. I've seen them weigh as low as 2.8 grams each. I would verify this is not the problem. Also, do you have a return line? New style fuel pumps make more pressure than old style ones.
    The weight of the floats checked in at 2.8g each. The new pump has three accesses IN, OUT, and VENT. The stuff looks very nice. The new carbs were $ 1100 something. Thanks for the reply.

  10. #10

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    Default Re: Carb flooding and venting, Kitfox4 912 UL

    Quote Originally Posted by Av8r3400 View Post
    Did they supply the red or black needles? I believe the red ones are softer and work better with the reversed intake manifolds on a Kitfox 4.
    The new needles were black.

    Thanks.

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