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Help 3LN1 Float heights

Discussion in 'Yamaha 250cc In-Line 4's' started by Forky, Jun 8, 2018.

  1. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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  2. Forky

    Forky Active Member

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    I’ve got 3x 5ct7 needles and 1x 5ct9 needle. I also have 3x 638 slide shaft thing and 1x 625




    5c428ede3b66c3a5f3228ea3f551d063.jpg


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  3. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    That is an N8 emulsion tube. Did you have your main jets mixed up with your pilot jets as @ruckusman advised, or do we just have to guess what you are doing?
     
  4. Forky

    Forky Active Member

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    That tube there has a bigger hole than the rest. The rest are the same.

    I’ve swapped the jet sizes around as old mate said on his comment


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  5. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    Then apart from all of the other things wrong with your carburettors, it is never going to run with the mains and pilots swapped.
     
  6. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    Because of the different series emulsion tube 625 & 638 that means that the main air jets and bleed jets will need to be different for that particular carb - you've basically got a mix and match set from 3LN1 & 3LN3 onwards

    You need to see if you can make matches of full sets of the various jets between the 3ln1 & 3LN3 carb sets from this page
    https://www.2fiftycc.com/index.php?...8-26mm-carb-settings-specs-3ln-3yx-zeal.9787/ - there's differences because of that different emulsion tube - it's kinda messy

    BTW - there is no issue with the different needles - if you read the bottom of the page I linked above 5CT7 & 5CT9 are interchangeable as long as the needle clip and 0.5mm shim washer are adjusted accordingly - one less thing to worry about
     
  7. Forky

    Forky Active Member

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    I didn’t have 100 mains, only 90. So after cleaning and sorting I’ve put it together and now seems to start and run fine. Took it for a 100m ride and is all good.

    Thanks greatly for your help and frustration
    You guys deserve a pat on the back!


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  8. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    OK it's worth cross referencing that table on the page I linked to ensure the sets of jets and emulsion tubes all match up because that larger bleed hole requires the different jets for that carb to work properly - looks like your carb sets were assembled from parts from a box from two models which got inadvertently mixed
     
  9. Forky

    Forky Active Member

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    I’ve done all that I could with what I had and information provided. I’ll be sure to jump back on those links at a later date to buy the correct fittings for the poor girl to be at her best. Hopefully it will only take me a few weeks to purchase required items

    Thanks


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  10. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    Yeah it's a choice between getting 3LN1 or 3LN3/5 sets of jets and bits - I believe the power output is the same between them, so consider that the 3LN3/5 might be an improvement of the carburation - someone with experience between both might be able to verify that.

    @Joker had some Keyster kits for sale, he may have put them to use, otherwise they'll sort you out
     
  11. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    Did you also pull out the needle and seat's?
    On top on the seat there is a fine wire mesh cage, that could have a lot of crud in it too.
    If you haven't taken them out, it might pay to check them too.
    And flush some fuel through there too.
     

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