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Mikuni Float Level Adjustment

Discussion in 'XJ Technical Chat' started by twerth, Dec 11, 2007.

  1. twerth

    twerth Member

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    I'm in the process of giving my carbs a good clean up, and I've run into a small problem. I have an '86 XJ700XS and the shop manual says the float level should be set to ~17.5mm prior to assembly and reinstallation of the carbs. When I took the carbs off, the floats were all in the neighborhood of 24mm and I don't think there is enough room to adjust them to the 17.5mm spec without running into interferance with the carb bodies. I'm wondering if the previous owner has swapped out floats or valves? Everything looks like the pictures in the manual. Any thoughts?
     
  2. fonz

    fonz Member

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    how exactly do you adjust the float level? i've taken my carbs apart two or three times now and never even heard of adjusting the level until the past few days when ive been trying to solve other problems.
     
  3. Fraps

    Fraps Member

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    twerth - are you sure you are measuring from the correct surface? That would explain the difference. I think it should be from the mating surface of the bowl and carb body.

    fonz - do a search of the forum for float level and you will find more info than you can read on the topic.
     
  4. twerth

    twerth Member

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    Yeah, I'm measuring it correctly. I've had Mikuni's on other bikes and never run into this before.

    BTW Fonz, I've attached the page from the manual so you can see what we're talking about.
     

    Attached Files:

  5. Fraps

    Fraps Member

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    well - likely you do have different floats. In that case you should concentrate on the fuel level height instead of the float height. I can't recall off the top of my head what the spec is but if you follow this link you'll see what I'm talking about.

    http://www.xjbikes.com/Forums/viewtopic ... level.html

    Good luck.
     
  6. Hired_Goon

    Hired_Goon Member

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    Are the floats in the right way round? Sounds like they are upside down.
     
  7. RickCoMatic

    RickCoMatic Well-Known Member

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    You can't put them on Upside-down and get the Float Bowl on.

    It's easier to do a Float Bowl Level Height and get the Level right than it is to do a measurement on all four.

    Start with using a piece of hose and get the Level of the one that's the best height.
    Then, you can use a Float Level Gauge to Dial-in the other three. You measure the distance from the base of the Float Valve to the Top of the Tang on the Float ... then, using the Value of the right one ... bring up or down the Tangs on the other three to match the measurement onn the one that is the correct base measurement.

    Most Speed Shops have the Gauge. Holley's are L-shaped and need to be trimmed to fit the width ... but has the most accurate scale for measuring.
     
  8. pjwilkinson

    pjwilkinson New Member

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    I am currently working on my floats from my 86 700-X and am having the same issue. I know that the floats are factory original. I know that the floats have some raise lines on them. Is it possible that these line are for the measurement instead of using the top/bottom of the float depending on which way you are leaning? I know most of you carb wizards use the fuel level, but with the pain of removing and installing these carbs, I would like to be correct the first time. Is this maybe a unique problem with the 86-x's with the mikuni carbs?
     
  9. RickCoMatic

    RickCoMatic Well-Known Member

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    No. It's because the Masterminds that write Repair Manuals treat Motorcycle D-I-Y'ers at the lowest common denominator.

    They'd rather we pull the Float Bowls three times than do the whole thing with a Float Measurement Gauge.

    I do the Measurement. I take the Float Level that's on the money and measure it with a Holley Float Gauge.
    After getting the Tab Height on the right one ... I measure it up and plaace the other three at that height ... once.

    You can't go wrong measuring them with a ruler made for the job.

    The Holley Gauge is a little wide.
    But, after making it narrow enough to do the measurement ... the measuring will put you at the same height across the board and you only have to adjust the Tabs ...

    Once!
     
  10. cereal_killer

    cereal_killer Member

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    Hey Rick! After googling "Holley carburetor float ruler", I have yet to catch a decent glimpse of what it looks like. Would you please post a pic when you get a free moment. I wanted to see how it differs from all those other float level gauges. Also, do you know of any e-tailers that stock them? Thanks!
     
  11. RickCoMatic

    RickCoMatic Well-Known Member

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    The Holley Float Level Ruler might be a thing of the past. I don't know how old mine is. I'm guessing "Mid-70's"

    Its a "L-shaped" Plastic ruler with a gradient along both axises. Like a miniature Framing Square.

    It comes in a Holley Rebuild Kit for the 4-Bbl Carb that fit the 76 Camaro LT.

    I have no more picture space. So, I'll have to snap a pic of it and put it on my website.

    But you dont need to have a Name Brand Ruler to pull-off the stunt.

    In a pinch ... you can use the Top to a Bic Pen.
    Take a razor and cut the pocket-clip flat and nip-off the end flat.
    Hold the "Cap part" and bottom-it-out next to the Float Tab that has the correct height.

    Make a line in the Plastic with an X-Acto Tool at the Tab Height.
    Match the Tab Heights of the other three Float Tabs to your line.

    Done.
     
  12. cereal_killer

    cereal_killer Member

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    Rick, Brilliant simplicity!!! I love it!!!

    Btw, I wasn't aware that you had your own website... url?
     
  13. RickCoMatic

    RickCoMatic Well-Known Member

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  14. jeepsteve92xj

    jeepsteve92xj Member

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  15. schmuckaholic

    schmuckaholic Well-Known Member

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    I'm at the same point right now, and there is no zarking way these things are anywhere near 17.5 - 18.5mm.

    (snippage)

    Noted and logged. I might stick that in the writeup, actually.
     

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