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Pinned Needles and needle jets/emulsion tubes - FZR250 Mikuni BDST28 Carurettors

Discussion in 'Yamaha 250cc In-Line 4's' started by GreyImport, Sep 17, 2016.

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  1. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    Hello ? :D

    yoy.png
     
    • Like Like x 1
    GreyImport, Sep 18, 2016
    #41
  2. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    The slide cutaways. 3LN1/3/5 are flat cut and 3LN6/7 & Zeal ones have round cutaways. I believe you mentioned that the rounded ones improved just-off-idle throttle response once upon a time?
     
    Linkin, Sep 18, 2016
    #42
  3. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    • Like Like x 1
    ruckusman, Sep 18, 2016
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  4. Joker

    Joker See "about me" for contact details. Contributing Member

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    Joker, Sep 18, 2016
    #44
  5. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    amazing amount of stuff on that site - the search however is totally useless
     
    ruckusman, Sep 18, 2016
    #45
  6. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    Yeah there's a lot of the same stuff listed.
    Apparently i'm a a priority member now that i've been asking question's through their 'help' link, lol
     
    my67xr, Sep 18, 2016
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  7. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    my67xr, Sep 18, 2016
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  8. Joker

    Joker See "about me" for contact details. Contributing Member

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    No... 100 pages of stuff couldn't seem to find it.
     
    Joker, Sep 18, 2016
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  9. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    my67xr, Sep 18, 2016
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  10. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    ruckusman, Sep 18, 2016
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  11. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    Yeah, there's 5 different seller's with them
     
    my67xr, Sep 18, 2016
    #51
  12. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    maelstrom, Sep 18, 2016
    #52
  13. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    The larger cutaway makes it leaner just for the first 1/4 throttle opening.
     
    maelstrom, Sep 18, 2016
    #53
  14. Gert

    Gert Well-Known Member

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    Hmm, does not sound good. We drove around 1.000 km's now with the Keyster and no trouble yet.
    If they go, I will order new needles and tubes from Yamaha. They are still available, very expensive, but not as expensive as an bike that does not run.
     
    Gert, Sep 21, 2016
    #54
  15. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    Speculation: I wonder if the hole in the slide has enlarged over time, so the needle can wobble more easily resulting in an increased wear rate
     
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    ruckusman, Sep 21, 2016
    #55
  16. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    Everything would start wearing Im sure right from scratch but as @Grasshopper eluded to , how long or how many Ks till it starts to affect performance is the unknown ... 5000? 10000? .....the @Linkin bike was still performing untill other problems caused its demise , as is the @Grasshopper 3LN3 after a few thousand Ks also and still going strong with the Keyster needles and tubes.

    Then there is the quality of the aftermarket replacements ..... I doubt they would stand the test of time like the originals.
     
    GreyImport, Sep 21, 2016
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  17. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    Ideally if the needles are held securely there should be little to no contact, or at least extremely minimal, so wear shouldn't occur at all.

    I'll hopefully have some solid inspiration, and a solution, when I pickup my zeal carbs
     
    ruckusman, Sep 21, 2016
    #57
  18. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    OH I should mention I've measured the upper diameter of the keyster needles, they are accurate to 0.01mm across all four, so perfectly consistent, if the needle jet holes are as accurate then they are as good as OEM IMO
     
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    ruckusman, Sep 21, 2016
    #58
  19. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    Heres wat the 3LN6 carbs were like when we pulled them down ..... but the the needles and tubes had no visible wear

    Wat causes the wear is the angle the carbs sits so the needle naturally falls onto the tube whereas with the newer design it is held central by the springed head

    http://2fiftycc.com/index.php?threads/linkins-fzr250-3ln6.2869/page-7#post-39218

    http://2fiftycc.com/index.php?threads/linkins-fzr250-3ln6.2869/page-7#post-43212


    Its wat they are made of that concerns me




    6 carbs 4.jpg
     
    GreyImport, Sep 21, 2016
    #59
  20. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    I've noticed that needle retention system was used in a lot of bikes, many pre-dating the Fizzers so I suspect Yamaha cheaped out on the original FIzzers in the slides, buggers!!

    It would be nice to know if there's a crossover between models with identical slides (which are available at a resonable cost) to retrofit them. Trying to cross reference Mikuni parts is a major PITA as the OEM carb components (needles mostly) seem to have mostly been customised to each individual model - trying to decipher Mikuni needles is just headache inducing.

    I was pondering reaming out OEM needle jets, getting a suitable larger diameter jet needles with correct taper to give the exact same fuel flow area at all openings, but there seems to be no certain way to know needle lengths because 5 series are longer than 50.00mm and shorter then 59.99mm
     
    Last edited: Sep 21, 2016
    ruckusman, Sep 21, 2016
    #60
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