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Project My FZR250 3LN6

Discussion in 'Your 250cc Projects' started by driftwood, May 10, 2020.

  1. driftwood

    driftwood Member

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    I'd been working on a plug foiling of #4, which has improved plenty with warming revs.
    #1 just began flooding. I dropped the fuel level to lowest of all by raising the float (pushing in tang). Still wet, wet, wet. What lets the bowl drain?
     
  2. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    You're chasing a related cause for two different problems, if the needle seats aren't sealing you will get flooding

    That needle seat and float height adjustment if it's incorrect will make it run either rich or lean depending on which direction it was adjusted incorrectly

    Dropping the fuel level won't correct a leaking needle seat - two possibilities, the needle tips are hardened &/or cracked, it's microscopic and can only be sen under magnification, that can only be solved by replacing them OR potentially there are pieces of gunk/rust or other material in the fuel system from perhaps the tank preventing them from sealing

    Are you running a fuel filter?

    For now stop adjusting the float height as you're just making work for yourself getting them back to where they should be, it's definitely not the cause of flooding

    Have you had the fuel line out of the bottom of the tank to check the filters?
     
  3. driftwood

    driftwood Member

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    I overfilled the bowl to see where it drained thru. Nothing.
    But after a few minutes of cranking, the manifold had 25ml of petrol - so inlet vacumn is dragging bulk fuel in.
    Re-inspecting seals etc saw me shear another bloody JPM11 capscrew, so waiting on delivery... again.
     
  4. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    I would think the fuel overflowing would be coming out the needle jet / emulsion tube
    Possibly leaking from the 4x pilot merge chamber hole's and pilot hole for the mixture screw but this would take a lot longer to drain 25ml's as the hole's are tiny
    The fuel level would have to be just under the Mikuni writing across the fuel bowl to leak out


    Hope you bought a spare Capscrew too if you've broken another one

    And which rebuild kit/s did you buy for the carby's ?

    [​IMG]
     
  5. driftwood

    driftwood Member

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    Damn. Thought I had it with a bad moulding in generic 5/16" O-ring... that blemish is hardened, but OTOH I never had overfull bowl with this float.
    2 cyls now randomly suffering drain from carby.
    Unable to see if there's meant to be an o-ring on the idle mixture screw?

    IMG_20200920_101116_692.jpg
     
    Last edited by a moderator: Sep 21, 2020 at 6:08 PM
  6. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    Yeah the 4x idle mixture screw's have a spring, then washer then o'ring
    The o'ring's and washer's normally stay at the bottom of the thread's in the carby body when you take the mixture screw's and spring's out

    [​IMG]
     

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