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Pinned FZR250 3LN1 carb service and tune

Discussion in 'Yamaha 250cc In-Line 4's' started by Oz_gone, Apr 2, 2015.

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  1. Oz_gone

    Oz_gone Member

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    After reading such thorough and informative posts about such things, I thought I would add to the wealth by documenting my carb service.

    Pics and settings to come.

    Please feel free to comment or add from own 3LN1 experiences ;)
     
    Oz_gone, Apr 2, 2015
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  2. Oz_gone

    Oz_gone Member

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    IMG_4457.jpg




    IMG_4458.jpg

    YKU carb 2 & 3 /// YKS carb 1 & 4


    IMG_4459.jpg

    LiteTek Viton kits A & B


    IMG_4461.jpg

    IMG_4460.jpg


    IMG_4466.jpg

    Needle from carb 1. Obvious signs of corrosion.

    Clip 3rd notch from top.


    IMG_4464.jpg

    Questionable detritus.
     
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    Oz_gone, Apr 2, 2015
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  3. Oz_gone

    Oz_gone Member

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    Needle jet from carb 2. also showing wear & corrosion.

    Both needles are marked 5TC7

    IMG_4468.jpg
     
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    Oz_gone, Apr 2, 2015
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  4. Oz_gone

    Oz_gone Member

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    :help:
    To save trawling the forum posts again...I remember there was mention of an irreplaceable spring somewhere in the carb setup.
    Anyone with more info?
     
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    Oz_gone, Apr 2, 2015
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  5. Oz_gone

    Oz_gone Member

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    Carbs 1 & 4 have jets 102.5 and carbs 2 & 3 have jets of 100.

    All four carbs also run 37.5 jets.

    IMG_4476.jpg
     
    Oz_gone, Apr 2, 2015
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  6. Oz_gone

    Oz_gone Member

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    :help:

    Are these supposed to be one way [PCV] air filters?
    The detritus in the diaphragm housing has either got there from the one way filter not working or perhaps the actual filter itself breaking down over 23 years?

    They look like they should have additional tubes but in every photo I've seen the just hang off the carbs as is.

    IMG_4481.jpg


    IMG_4482.jpg
     
    Oz_gone, Apr 2, 2015
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  7. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    Jets.jpg
     
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  8. Oz_gone

    Oz_gone Member

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    Is there a particular method for removal of emulsion tube other than gentle drift [tap tap]?
     
    Oz_gone, Apr 2, 2015
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  9. Grasshopper

    Grasshopper Well-Known Member Dirty Wheel Club

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    Nice work... your gonna love your bike after this rebuild :thumb_ups:.. I just did the needles and emulsion tubes and clean at this stage... and Wow!
     
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    Grasshopper, Apr 2, 2015
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  10. Oz_gone

    Oz_gone Member

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    Gentle tap downwards is the win. Thought they came out upwards. The black seal was actually dirt at the base of the emulsion tube.
     
    Oz_gone, Apr 2, 2015
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  11. Oz_gone

    Oz_gone Member

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    Anomaly.

    Carb 1 Emulsion tube has a very small nylon washer. None of the other carbs have a similar part.

    IMG_4488.jpg
     
    Oz_gone, Apr 2, 2015
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  12. Oz_gone

    Oz_gone Member

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    OEM Emulsion tubes are stamped 638 and N-6

    The replacement ET's and needles have no stamp whatsoever.

    IMG_4489.jpg



    IMG_4490.jpg
     
    Oz_gone, Apr 2, 2015
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  13. Oz_gone

    Oz_gone Member

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    Idle mixture needle. All four showed wear & corrosion.

    Also note washer which sits above spring.

    IMG_4491.jpg
     
    Oz_gone, Apr 2, 2015
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  14. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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  15. Oz_gone

    Oz_gone Member

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    Cheers Grey!
    Totally would not have realised those rubbers were down in the bowels without that post!
    All 4 successfully removed ;)
     
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  16. Murdo

    Murdo The Good Doctor Staff Member Contributing Member Ride and Events Crew

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    Watching with interest as have Robbo's 3LN1 carbs to do.
     
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  17. Oz_gone

    Oz_gone Member

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    :help:

    Removing the slide housing to fit slide housing O ring [LiteTek OR-018 that replaces 003] is currently baffling us.

    Result = Put finger in and pull!

    :party:
     
    Oz_gone, Apr 2, 2015
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  18. Oz_gone

    Oz_gone Member

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    Slide housing and well rigid O ring.

    IMG_4492.jpg
     
    Oz_gone, Apr 2, 2015
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  19. Oz_gone

    Oz_gone Member

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    Choke plunger set up with Viton replacement. Hoping not to have the split the carbs if possible.

    IMG_4493.jpg
     
    Oz_gone, Apr 2, 2015
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  20. Oz_gone

    Oz_gone Member

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    Float needles.

    Before. No bounce.

    IMG_4494.jpg


    After. Bouncy, bouncy :D

    IMG_4495.jpg

    I imagine if the rest are the same then the excess fuel / bogging issue would have a lot to do with this...Not cutting off fuel supply, rich mixture etc etc.
     
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