Carb float needle seat

Discussion in 'Finished Projects' started by digiex-chris, May 2, 2015.

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  1. May 2, 2015 #1

    digiex-chris

    digiex-chris

    digiex-chris

    Well-Known Member

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    A friend stopped in on Sunday with a dirt bike carb that had a float needle seat in rough shape. Kawasaki says non-replaceable. A lathe says otherwise.

    Here's the carb with the seat pulled (using a tap)

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    And the seat, with the needle, threads cut by the tap used to pull it

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    Some nice brass
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    Turned to .3873" (the size of existing one, polished in the last few ten-thousandths). Then I made a D-bit reamer, and smoothed the hole walls and flattened the bottom of the hole. I didn't get pictures of that.

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    I guessed that since the needle tip was very very close to 60 degrees as measured with the mark 1 eyeball, that it was likely that the seat angle was made by an angle that's extremely common in the machining world, 60 degrees. A lathe center drill was an obvious choice. So I gave it a try.

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    Parted off, then off to the mill to drill the transfer port holes. Sorry, no pictures of that either. Then I reset the float tang to be horizontal, since I didn't have a good indicator of existing float height before I started due to the seat condition. Then I pressed the new seat in a bit at a time until the float height was to spec.

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    And using the KLR650 I have to provide about 25 inches of head pressure (way more than a KDX can bring to bear)

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    No leaks! And for giggles I whipped up a fuel level gauge that screws into where the drain plug goes.

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    It took me 4 tries to do it. Inopportune entrances into the shop by observers distracted me and I took out the first 2, all with mistakes in polishing in that last ten thousandth to match the press fit as close as I could. The third one I forgot to drill the transfer ports until after I'd pressed it home. The last one I made a 60 degree point on a close fitting aluminum rod to lap the seat angle, but it leaked. I used the center drill, shimmed straight with paper, to touch it up again by hand, and it quit leaking! #4 is the winner.

    Just because the manufacturer of something says it's garbage doesn't mean it's not fixable.
     
    Last edited: May 2, 2015
    canadianhorsepower, akitene and gld like this.
  2. May 2, 2015 #2

    barnesrickw

    barnesrickw

    barnesrickw

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    I think it's great to be able to help people out with the skills you have. You will be a neighborhood legend.
     

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