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Thread: Air intake danger

  1. #1
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    Default Air intake danger

    I would recommend to everyone that they take extra care in inspecting the the air intakes tubes on their Carbon cubs the next time they have the chance.

    I had one work loose and while it very luckily happened on the ground, it would have been a disaster just a few minutes earlier. The flexible plastic tubing that connects the metal intake for the the right rear cylinder worked loose as you can see in the attached picture. This resulted in a huge vacuum leak. This caused the engine to quit when power was reduced below 2000 rpm. I would recommend everyone inspect this area. My other intakes seem fine. In looking at it it doesn't seems like it would be able to come loose but obviously it can.

    Has anyone else had this issue? I have a little over 400 hours on my engine.

    Blu
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    Last edited by fencer; 10-14-2012 at 08:15 AM.

  2. #2
    Senior Member Pete D's Avatar
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    Default Re: Air intake danger

    That looks like the result of a kickback or a backfire on startup?
    Pete Dougherty
    R & D Shop Manager
    Cub Crafters Inc

  3. #3
    Senior Member Clay Hammond's Avatar
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    Default Re: Air intake danger

    Where's your hose clamps?

  4. #4
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    Default Re: Air intake danger

    i suppose a backfire is a possibility, had't thought of that, although i didn't hear one.

    Are there supposed to be hose clamps?
    i didn't think it came with them.

  5. #5
    Senior Member Clay Hammond's Avatar
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    Default Re: Air intake danger

    Quote Originally Posted by fencer View Post
    i suppose a backfire is a possibility, had't thought of that, although i didn't hear one.

    Are there supposed to be hose clamps?
    i didn't think it came with them.
    Sorry. Got turned around looking at your picture. Thought I was seeing front primary intake. Disregard.

  6. #6
    Senior Member Pete D's Avatar
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    Default Re: Air intake danger

    Quote Originally Posted by Clay Hammond View Post
    Where's your hose clamps?
    No hose clamps. Carbon Cub intakes don't have traditional thick, heavy hose and clamps. They have a couple of layers of heavy duty shrink tube, one of which has an adhesive inside of it. I believe that technology may have been developed from Reno air racing?
    Pete Dougherty
    R & D Shop Manager
    Cub Crafters Inc

  7. #7
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    Default Re: Air intake danger

    Quote Originally Posted by fencer View Post
    I would recommend to everyone that they take extra care in inspecting the the air intakes tubes on their Carbon cubs the next time they have the chance.

    I had one work loose and while it very luckily happened on the ground, it would have been a disaster just a few minutes earlier. The flexible plastic tubing that connects the metal intake for the the right rear cylinder worked loose as you can see in the attached picture. This resulted in a huge vacuum leak. This caused the engine to quit when power was reduced below 2000 rpm. I would recommend everyone inspect this area. My other intakes seem fine. In looking at it it doesn't seems like it would be able to come loose but obviously it can.

    Has anyone else had this issue? I have a little over 400 hours on my engine.

    Blu
    Yes I had a string of them early on and the intake tube coming off is a result of backfire. The intakes are not under pressure , actually I think a small suction so they need to be sealed or you will have an induciton leak which will lean the engine and or cause it not to start. They can be repaired quite easily with new shrink tubing ( there is an inner and an outer size for each tube). Thanks to Randy we figured out my problem was that that one of the plug wires was too close to the ignition leads ( should have at least an inch clearance) which on startup was causing one of the cylinders to fire early and hence a backfire.. A backfire did not always result in an intake tube coming loose but eventualy would. I have not had the probelm now that I zip tied the plug wires away from the ignition leads. Regards Gary

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