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Setting the floats (Mikuni), not gettin any readings FIXED

Discussion in 'XJ Technical Chat' started by broberg, Nov 2, 2012.

  1. broberg

    broberg Member

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    Hi

    I'm trying to set the correct float height since I renovated the carbs.

    But the thing is I don't seem to get any wet level to measure, I'm guessing, just guessing since I don't have a perfect fit nippel, air gets in and somehow f*cks it up.

    Or the pvc-tubing is to long. I don't really know.

    When I open the drain with nothing connected it flows as it should.
    But when I'm connecting the pvc-tubing it just fills a bend (se illustration) and then stops?
    [​IMG]


    I'm gonna try and find something that is a really tight fit for it, but whats the expertises verdict?
     
  2. ManBot13

    ManBot13 Well-Known Member Premium Member

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    Re: Wet setting the floats (Mikuni), not getting any readings

    For one, you need fuel flow into the carbs. This means that the petcock needs to be ON if using ON-OFF(-RES) valve, or PRI if using ON-RES-PRI valve. draining fuel into the tube for measurement reduces the amount of fuel in the bowl, so the bowls need to be able to fill up until the float shuts off flow.

    There also has to be no air between your fluid and the outlet of the carb. In your drawing, the bubble to the right of the fluid prevents a proper measurement. Remedy this by maneuvering the tube such that the air can work it's way to the open end of the tube, once you have a contiguous column of fluid with no air, then you can lower it (so that it bends downward) and take your measurements.

    Also, make sure your drain valve is sufficiently open.
     
  3. broberg

    broberg Member

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    Re: Wet setting the floats (Mikuni), not getting any readings

    the flow of gas is constant with the rig I currently use.
    But The thing I'm worrying about doing what you say (ie first lower the tube so there is no air in the tube) is that if I let it go to far I get an incorrect amount of gas in the tube and therefore the level in the tube can be higher then the one in the carb. Or am I thinking wrong?
     
  4. ManBot13

    ManBot13 Well-Known Member Premium Member

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    Re: Wet setting the floats (Mikuni), not getting any readings

    1. When you first open the drain valve, bend the tube upward such that no bubble forms. There will be very little fuel and the tube, and you can't take a measurement in this position

    2. Bend tube downward and position such that the meniscus will line up with where you want to measure it. Since you removed air in the first step, bending the tube downward will cause it to fill with fuel only. The level on the tube is equal to the level in the bowl due to hydrostatic pressure.

    You are correct that it is possible to fill the tube with more gas than the bowl can hold, giving you a false reading, but you can always remedy this by lowering the tube further, taking on more gas (and thus the bowl has to fill more). As long as you don't fill the tube, then lift it back up, you measurement will be accurate.

    If you over fill the tube, close the drain valve, empty the tube, and try again.
     
  5. broberg

    broberg Member

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    Re: Wet setting the floats (Mikuni), not getting any readings

    It all seems so obvious now, thank you for setting my mind straight!
     
  6. broberg

    broberg Member

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    Re: Wet setting the floats (Mikuni), not getting any readings

    Okey, Now I'm getting readings but, what the hell!


    One minute a carb is overflowing, drains and fix the level on that carb,then it's fine for about 3-4 drains then (without me changing that float) it overflows again?!

    I'm getting quite ... annoyed, drained and adjusted the floats about 50 times now..

    anyone else had these much problems setting their float levels?
     
  7. ManBot13

    ManBot13 Well-Known Member Premium Member

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    Re: Wet setting the floats (Mikuni), not getting any readings

    I did on my turbo seca mikuni carbs. I got new float valve assemblies from BDesigns, and thoroughly recommend him, chacal only had yamaha parts that were 4x the price. If he doesn't make them, send him an email.

    I was also measuring float level from place wrong place. But if the float level isn't consistent, the valve is likely suspect.
     
  8. Rhettb3

    Rhettb3 Member

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    Re: Wet setting the floats (Mikuni), not getting any readings


    I'm in the same boat right now, (even had the "fluid only fills the bend" problem) and that's with all new needles and valves. I find that if my homemeade nipple isn't fully seated in the drain, I get the big bubble, just gotta re-adjust and hold the tube as manbot said.

    I have been letting the carbs fill up, then just go through and drain a bit of gas from each carb once or twice, don't even bother taking a reading at first. Seems like when they fill up the first time the fuel level is a bit high but it settles out after the valve has been "worked" a bit.

    Another idea might be to look over your floats for cracks or other defects. I was starting to suspect mine when my readings were going all over the map, but that was before I learned to take several readings before making TINY float adjustments.
     
  9. schmuckaholic

    schmuckaholic Well-Known Member

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    Re: Wet setting the floats (Mikuni), not getting any readings

    Gentlemen.

    I too have had that problem -- fought with it for months before I finally figured out the problem. It's likely a float issue (obviously) but not what you think.

    You're all too familiar by now with the tang that the float needle sits on. There is another -- in the setting the fuel levels writeup, on page 5, look just to the left of the red box -- that tang dictates how low the floats can hang.

    The issue? The floats are sitting too low with the bowl empty, the needle is being pulled off vertical, and it's binding in the seat.

    Once I figured that out, my problem magically vanished and the fuel level measurements dropped right into place.
     
  10. chacal

    chacal Moderator Moderator Supporting Vendor Premium Member

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    Re: Wet setting the floats (Mikuni), not getting any readings

    Good catch schmuck!
     
  11. broberg

    broberg Member

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    Re: Wet setting the floats (Mikuni), not getting any readings

    Let's see if I understood you correctly, so you say something like this happen cause of to much travel downwards? :

    [​IMG]
     
  12. tabaka45

    tabaka45 Well-Known Member

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    Re: Wet setting the floats (Mikuni), not getting any readings

    I had the same problem with one carb. I removed the seat, pin, and float and used 2000 grit wet/dry sand paper and polished the end of the spring tip on the needle pin, the four corner edges of the pin, the float mounting pin, the lip on the float that contacts the needle, and the inside of the valve seat. I even used a tooth pick and 2000 grit and cleaned the inside of the float hinge. Since mine were old needles I cleaned the rubber tip with a q-tip and carb cleaner and immediately washed them with fresh gas. It has been hooked up to a free flowing gas source for about 3 hours with no leak or over flow. I've even lightly shaken the carbs numerous times with no change. I'm leaving them hooked up until tomorrow afternoon, and if there are no leaks or overflow I'll re-install the carbs. I've read in other posts where folks had to do the same thing to new valve seats and needles to get them to work.
     
  13. schmuckaholic

    schmuckaholic Well-Known Member

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    Re: Wet setting the floats (Mikuni), not getting any readings

    Precisely.

    A better view of the other tang I'm talking about can be seen in this file, at the top of page 18.
     
  14. broberg

    broberg Member

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    Well, Schmuck saved my sanity! I have now solved my issues and gotten the carbs to the correct fuel level (+/- 1mm as allowed)

    I adjusted the "drop-stop" so it only let the float valve needle traveled apx. 1-2mm.

    I figured if you close it to much it will not let fuel in fast enough, but with a 1-2mm play up and down the needle doesn't get a chance to get "stuck" like mentioned above. Or at least the risk of it is minimal.

    Notice that I have brand new seats and needles, if you don't have new seats and needles, make sure that the needle runs freely in the seat and that the rubber tip of the needle isn't worn, broken or dried out. (se tabaka45's post above)


    Again, Thank you Schmuckaholic!
     
  15. schmuckaholic

    schmuckaholic Well-Known Member

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    ...at the cost of my own. :mrgreen: Another satisfied XJBikes customer...
     

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