ZipTy FCR idle mixture screw in a BST

Discussion in 'Thumpers' started by creeper, Feb 14, 2005.

  1. meat popsicle

    meat popsicle Ignostic

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    wasn't planning on packing it anywhere past the driveway outside my garage... ya wanker :D especially with the BST being so sociable and all.

    but if there is a screw that eliminates the fangled screwdriver then so be it. thanks for the heads up! :thumb
    #21
  2. accadacca

    accadacca Hard Rocker

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    AMEN Brutha!!!! :dunno
    #22
  3. accadacca

    accadacca Hard Rocker

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    :lol3 After knowing about the screw from day one, it gave me a good laugh to see your screwdriver. :grinner

    We'll have to wait and see what the creepster thinks? :ear
    #23
  4. creeper

    creeper Still alive...

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    Went for a little ride finally to get things all warmed up and this is what I found:

    Bike idling at 1700 rpm, with the mixture screw set at 2 turns out as a starting point.

    I turned the screw in and saw no noticable change in idle speed until screw was 1/2 turn out from seated... engine abruptly died at 1/4 turn out.

    Turned screw out to three and one quarter turns before it started to run rich and idle went down and it died at three and one half turns.

    The interesting part is no noticable change in idle speed from 1/2 turn out to three and one quarter turns out... a net range of two and three quarter turns where not much of anything happens.

    This may all change a bit when I get a chance to go out in the dirt and get the engine and carb good and hot... but I doubt it.

    Conclusion? As this screw is more abrupt in taper than the stocker, it makes sense that it would respond like this. The tapers are not a close match, without a finer relationship, fuel flows at about the same rate until the screw is near completely closed or open.

    Dag has mentioned that he might have a buddy make a "long screw" on CNC with the standard BST taper on it... This will be the hot tuna.

    If anyone wants to try an econo version as an experiment, you could do what I've done many times (years ago) on Harley fixed venturi Keheins, which is to get a Harley throttle stop screw, which has a big plastic thumbwheel on it, drill a short hole into the top of the mixture adjuster screw and solder or epoxy the two together.

    Th Th Th That's all folks...
    #24
  5. Loadedagain

    Loadedagain making chips

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    git me dimensions will yerz... i'll blast a couple off if you would like.... sir.
    #25
  6. SoilSampleDave

    SoilSampleDave Dr. Zaius was right!

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    I would be happy to trade a little cash for one of those...
    #26
  7. creeper

    creeper Still alive...

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    They is on the first page pookie poo... not perfect 'cause that little point is tough to measure with conventional instruments. :D
    #27
  8. Loadedagain

    Loadedagain making chips

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    and i would be happy to take your cash....

    lets get me dimensions and i'll make a few first. then we'll take this to the vendor forum.
    #28
  9. Loadedagain

    Loadedagain making chips

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    you callin him pookie pooh, or me?




    and thanks for pointin that out. i aint all that swift today.
    #29
  10. Loadedagain

    Loadedagain making chips

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    yo creepy... you know what the threads are?
    #30
  11. dagwood

    dagwood Banned

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    I'd need to have Claude put them in the comparomitor to get the true demensions. it's real hard at that size to duplicate measurements by hand.
    go for it Loaded. it would cost me money even if he is a friend he has to make a living and pay off the Tsugami. Hard anodizing would cost some to. make mine orange.
    :deal
    I'll be first in line if you want to sell them though. :thumb
    #31
  12. Loadedagain

    Loadedagain making chips

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    i'll have a look tonight. shouldn't be too bad.
    #32
  13. creeper

    creeper Still alive...

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    So... Dag gets the comparitor numbers and thread pitch off a stocker and you add a bit with a knob... viola! You gotcher screw pookie. :lol3
    #33
  14. accadacca

    accadacca Hard Rocker

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    :nod
    Huh........Ok! :dunno

    My bike seemed to run the best at 1.5 turns out as per the instructions. It would bog a bit when reving in other positions. Could have been cold? As far as the idle, I used the idle screw for that and it had no problems. I am sure that you could make something better. My Dad has a full year of riding with his and no complaints. 4000ft to 10,000ft and around 1000mi. I will run this screw until I find a problem with the performance.

    I love this carb! :thumb I have only ridden around the block a couple times. But this BST was such an improvement over my dellorto. I may not notice any fine detailed stuff until down the road. BST! :nod
    #34
  15. creeper

    creeper Still alive...

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    Piece O cake for you pookie poo. :nod

    LOADED'S RISERS AND BST 40 EXTENDED MIXTURE SCREWS LTD.
    #35
  16. creeper

    creeper Still alive...

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    But... the instructions are for an Kehein FCR, not a Mikuni BST40. I'll keep playing with it... initial impressions are apt to change.

    Gota go... new glasses for me! :clap
    #36
  17. Loadedagain

    Loadedagain making chips

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    yeah.... now all i have to do is get that bitch outa there without disassembling my whole flippin bike.
    #37
  18. dagwood

    dagwood Banned

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    :lol3 don't limite your market to much there.
    theirs a couple other things you could spin off.
    Say hard anodized 7072 front wheel shim. :thumb
    or maybe swingarm chain adjustment blocks with real marks on them.
    let me think and you could have a whole line of must have parts. :ear
    #38
  19. dagwood

    dagwood Banned

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    triphocals yet? :blind :dude


    hey loaded. loosen boots, twist carb to left, use screwdriver. easy :lol3
    #39
  20. Loadedagain

    Loadedagain making chips

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    hey.... you're a fart smeller!
    #40