Carburetor flooding - Pressed in float valve seat damaged :-(

Discussion in 'Motorbike Technical Discussion' started by PrizM, Sep 15, 2006.

  1. PrizM

    PrizM Guest

    Hi everyone,

    I recently thoroughly cleaned my Keihin CVK34 carburetors from my old
    ZX750R '87. The carbs were really clogged with varnish since the bike
    had been sitting there for about 2 years. But now, if I put the
    petcock in "prime" position (motor stopped) i get a slow but constant
    dripping of gas out of the carbs. Unfortunately, during my (too)
    intensive cleaning session i think i might of lightly scratched the
    float valve seats leading to an improper sealing. I tried changing
    float needles with no success. What's even more unfortunate though is
    that those ($&%@!!!) Keihin carbs have pressed in brass valve seats.
    All this meaning i would have to change all four carbs all together to
    resolve my problem... at 1400$ the set... I better salvage the bike!
    Which i don't want!!! So my question would be if anyone has any idea
    how I could try to have those brass seat replaced or reseated?
    Any suggestions... I'm desperate!

    I was maybe thinking with a sharpened metal rod at the right angle (a
    bit like a pencil) and some valve lapping compound???

    ....or a machine shop?


    PrizM, Sep 15, 2006
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  2. PrizM

    clay Guest

    I doubt you scratched the seats. Just removed varnish that was filling
    in erosion on the seats. Pointed steel rod with lapping compound, so
    long as it is close to the same angle as the needle. A drill press will
    help, as you want to keep the rod as straight as possible. Replenish the
    lapping compound a lot.

    Or you can get a very small o-ring and poke it down the seat hole. Get
    one from a lawnmower shop.

    clay, Sep 16, 2006
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  3. PrizM

    B-12 Guest

    Individual carburetor assemblies list for $400, you wouldn't have to
    buy the set to get one new carburetor. Look at the carburetor assembly
    fiche at

    The carb assemblies are 15002XXXX but $400 is still ridiculous to solve
    this problem.

    If you look at the carburetor parts fiche, it shows the "mixing
    chamber" as being something like 16002 and points to the vacuum cover.
    I suspect that is wrong, because the "mixing chamber" should be the
    carburetor body.

    Whatever. I wouldn't try to buy a new carburetor body until I attempted
    to lap the brass seat with some kind of home made tool and fine valve
    grinding compound.

    The conical end of the float valve probably has to just mate with a
    cylindrical hole
    in the brass seat, I doubt if the seat would have a mating taper.

    When there was some varnish on the float valve seat of my KLR, I just
    put some fine emery cloth on the end of a small diameter plastic tube
    and spun that home made tool a few times, examined the seat with a
    magnifying glass, and reassembled the carb.
    B-12, Sep 16, 2006
  4. Filed under 'useful tips' section.

    I likes that.
    The Older Gentleman, Sep 16, 2006
  5. PrizM

    PrizM Guest

    Clay: I kinda like the idea of the o-ring down the seat hole... could
    be good. But i would have to bend the float arm of the same distance in
    order to keep the same level of gasoline in the bowl.

    B-12: Thanks for the insight on the part # of the carburetor body, i'll
    check with my dealer.
    There is a mating taper on these... i guess it prevents somewhat the
    wear of the rubber cone on the float needle.
    PrizM, Sep 17, 2006
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