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  1. #1

    Default KEIHIN butterfly float

    Can anyone out there tell me how to set the float level on my carb I know that the float level is off but I'm not exactly sure where to get my measurements from any help would be appreciated
    Attached Thumbnails Attached Thumbnails IMG_20200810_163250374.jpg  

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    Nice bike,,,,,

    How do you know it's off if you don't know how to set it??????? Just a question...........

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    found this:

    Rebuilding the Keihin Butterfly Carb

    ...The float needle should just kiss the seat with no extra pressure. Aftermarket float valves have a spring loaded pin under the float tab. So when the valve tip closes onto the seat, you can still push the valve down further. The valve should 'just' close when measuring the float level. Pushing further in from there will not close the valve any further. But it will cause you to set the float level wrong. The valve should be a light seat when measuring. Some aftermarket float needles with the spring loaded pin also have a defective neoprene tip on the other end (which does not seal even when set right). 13) Since the tip on the needle on aftermarket ones don't work well, some would use the old original one (solid pin) to get a better measurement. 14) Beats assembling the carb only to have it sit there and flood with gas. Also make sure you have the float valve for the correct type of Keihin carb. The aftermarket valves are a little taller.
    Click image for larger version. 

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    EDIT: Jim commented in post #6 below about the float needles ^^^,so sharing it here:
    "...The butterfly Keihins came with a three sided needle. The CV Keihins had the four sided needle (and the last of the butterfly models may have had a four sided needle as well, but they are different lengths). I have found that the caution that the aftermarket four sided needles won't seal is correct. They are ABSOLUTE JUNK.

    Float Level Adjustment.
    The measurements in the FSM are a reference point that will keep the OEM float within a fully open and fully closed position.
    Using aftermarket parts, you may have to adjust some.
    depending on the year; 76-78 Sportster carbs:
    Two positions of the float valve must be set; The valve fully closed and The valve fully open.
    Setting the closed position lower will tend to make the carb act lean at low speed.
    Setting it higher can cause rich running, flooding and dribbles out the overflow line.
    Equally important is to set the wide open float setting by bending the other metal tag on the float by the pivot.
    This makes sure the float needle fully opens at full throttle openings and allows full fuel flow without starvation.
    It also stops the float hitting the bottom of the float bowl and possibly getting damaged.
    Fully closed measurement: Tip the carb upside down so the float assembly is facing up.
    Measure from outside surface of the float to flat mounting surface of the carb body casting.
    Measurement: 9/16” to 5/8” (14mm-16mm).
    Fully open measurement: Next turn the carb over (right side up).
    Measure from the same surfaces as above (outside surface of the float to flat mounting surface of the carb body casting).
    Measurement: 1-3/32“-1-3/16” (28mm-30mm).
    Click image for larger version. 

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    79-87 Sportster carbs
    There is only one measurement to set with these.
    Turn the carb body sideways as shown below.
    The valve should be fully closed with a measurement of .63“-.67” (16mm-17mm) from the top of the float to the bowl mounting surface.
    Click image for larger version. 

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    http://sportsterpedia.com/doku.php/techtalk:ih:carb01q


    Thread: Give your Ironhead Keihin another shot!

    "a lot of people say these carbs are junk and i will have to personally disagree. Heres a letter i wrote to somebody a while back who was having some problems so i took all of my research and trial and error and put it into one page for him and thought i would copy and paste it for everyone to look at.
    I still love the S&S carbs so dont get me wrong but for poor folks like myself, this only costs around $40 with some time and patience, and it actually works. Good luck.


    well i have a 1000cc and i used the .88 slow jet and 1.80 main. im pretty sure some guys are running close to the same jets for their 900cc bikes.
    you should just worry about the slow jet first. i would start with a .75 and then move up from there. you can usually tell if you have the right size by starting it. just let it warm up for a minute or so and if it still farts every once and a while you need to move up a size. i put a .80 in mine to make sure and once it warmed up i got the farts every 5 or 10 seconds.
    when you need the choke to start just move it up between the first and second click is perfect.once you get the slow jet right start with a 1.70 or 1.75 and get goin at full throttle in 4th gear and when you let off to about 1/2 throttle it shouldn't surge or bog. if it bogs go up in size, surge go down.
    you can get all the jets from J&P just look at the pic first and make sure they look the same because sometimes they label them wrong as if it goes to a cv carb. but they might have fixed that.
    Get an andrews accelerator pump also. i had to get mine off of ebay because i couldnt find anyone else that sold them and make sure it is for the butterfly carb. it should come with the instructions that shows u where to drill a small hole and what size drill bit u need.
    in the early 80's harley made a more emissions friendly version that sucked and restricted the ammount of fuel flow. the andrews pump brings it back to the 70's standard gas pumper. make sure that when you turn ur throttle that the fuel streeam goes right down the middle of your carb and not towards the back cylinder. just twist the nozzle with some pliers once u have the bowl back off.
    now the fuel mixture screw is under a cap at the top of the carb closest to the motor. drill a VERY shallow small hole in the top and pry that sucker off. you can choose to leave the stock mixture screw in there but it will be a bitch to get a screwdriver in there with your tank on.
    CV Performance has a mixture screw that you adjust with your finger that looks slick. i scribed a little mark in mine that way i could tell the amount of turns i made.
    on your carb there is a plastic cam on the right outside with a predrilled hole in it where a limiter screw would go. I found it best to run a cheap sheetmetal screw in it and round the tip off so it wont scar your carb body and screw it in until its about 1/4 inch space at full throttle but some people like just leaving it alone and getting the full stroke of the accel pump but ive heard that with some people theres a problem with the slow/main jet transition when they leave it alone.
    and finally if you are running drag or open pipes you have to baffle it a little or it will bog every time your main starts to open and you will never make it past 50mph.
    i have the can opener style that i cut down to 2 inches and bent the can opener looking tabs back to point towards the rear. it wont sound baffled but you need that back pressure or you will be way too lean all the time.
    the reason everyone hates these carbs is that they dont want to take the time to learn about them. i like my butterfly better than my old super e.
    and another thing is that when u get thhat sucker tuned right you can kick it over in 1 or 2 kicks when its 32 outside. they are great carbs just dont get discouraged with it. there is always a way to fix its problems. theres a lot of stuff on xl forums too like how to clean it out right by plugging certain holes and spraying in another to clean out the passages and what height to set the bowl's float at and stuff like that but i cant remember at the moment. if u cant find them hit me up but i think i covered all the problems with em. good luck and dont give up. just hit me up if u need help."

    http://www.chopcult.com/forum/showthread.php?t=16542
    Last edited by TriNortchopz; 08-31-2020 at 11:14 PM. Reason: JBinNC comment added

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    .



    Brass high flow carburetor fuel inlet replaces broken fuel inlet to the carburetor bowl for modified engines. For all Keihin carburetors.
    Carburetor side diameter is .311" and the hose size diameter is .270".

    FITS
    FL 1976-1984
    FXR 1982-1994
    FXD 1991-2017
    XL 1973-UP
    FLST 1986-2017
    FX 1976-1984
    FXST 1984-2017







    Last edited by Dragstews; 08-31-2020 at 8:43 AM.

  5. #5
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    Go really advanced by adding these............
    Attached Thumbnails Attached Thumbnails MVC-002S-6.JPG   MVC-001S-6-2.JPG   MVC-003S-4.JPG  

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    Referencing the pictures in post #3, the four sided needle is identified as the original part. That is an error. The butterfly Keihins came with a three sided needle. The CV Keihins had the four sided needle (and the last of the butterfly models may have had a four sided needle as well, but they are different lengths). I have found that the caution that the aftermarket four sided needles won't seal is correct. They are ABSOLUTE JUNK.

    Here's another problem that has not been discussed:
    The bowl overflow standpipe in the butterfly carbs is prone to crack. That will cause the carb to piss fuel out of the overflow hose constantly. That tube can be replaced by chasing it out with a pin punch from the bottom, and replacing it with some 1/8" brass hobby tubing. The original is slightly larger, so you need to tin the replacement with solder to make up the difference. The length of the tube is important!

    Jim

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    Found this CC thread:

    2015 Thread: Shovelhead - Any Keihin Butterfly Carb experts?

    Tattooo: "All the info you need is in one of the old Easyrider trix books. I don't remember which one. I have it saved but for some reason I can't get it to open....

    "It's in tips and tricks 2. Page 34..."

    Tattooo: "Yea that's it. It's on page 34 35 36 and 37. The hop up tips are on 26 and 27.... I got it to open but I can't get it to copy yet... LOL Hell I'm getting there... I did the hop up tricks on my 79 FXS and haven't had a bit of troubles... "
    http://www.chopcult.com/forum/showthread.php?t=41483


    Easyriders Tech Tips & Tricks, Volume 2, download free pdf:

    https://drive.google.com/file/d/0B4s...5OVm1FYWM/edit



    links to all 4 Easyriders TechTips & Tricks in this site:
    Service Manuals
    Free manuals and documents:

    Harley Easyriders Tech Tips & Tricks v.1.pdf
    Harley Easyriders Tech Tips & Tricks v.2.pdf
    Harley Easyriders Tech Tips & Tricks v.3.pdf
    Harley Easyriders Tech Tips & Tricks v.4.pdf
    https://harley.manuals.cc/p/harley-r...QbmFDvnydfn68E

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    I'd still like to know why he thinks his float is off?????????????

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    I check questionable carbs off the bike with a dummy tank (outdoors) with float bowl removed to actually see when fuel flow stops.
    I then install the bowl and hold the carb at different (reasonable) angles to see if it starts flooding.

    We sold or gave away many takeoff big twin Keihins to Ironhead owners who liked them as replacements for worn Bendix carbs.

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