The BST-40 Bible

Discussion in 'Thumpers' started by laramie LC4, May 31, 2008.

  1. theGrinch

    theGrinch SNF Dream Riders

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    Derek,
    PMed you, could you give me a call?
    Thanks,
    Peter

    .
  2. rockscrambler

    rockscrambler rock climber

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    yes, its in the pic "one of these". and is the smaller vacuum line, do you know what that connects to on the other end? thanks guys!
  3. joefromsf

    joefromsf Dark Happens

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    It doesn't connect to anything. It vents to air and is routed inside the outer frame back past the battery. It ends just past the battery.
  4. ER70S-2

    ER70S-2 Long timer

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    This one:
    [​IMG]

    Goes here: Pay attention, the photos will mislead you. The 1st pic shows the hose goes to the left, the second shows the hose comes in from the left (backwards).
    [​IMG]
  5. joefromsf

    joefromsf Dark Happens

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    That's what I get for trying to answer from memory. So it ends before the battery. I was right about venting to air though. :lol3
  6. ER70S-2

    ER70S-2 Long timer

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    Close enough. :deal
  7. motolab

    motolab Long timer

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    Interesting that CARB allows anything that vents fuel to go to the atmosphere. I would not have expected that.

    Regards,

    Derek
  8. rockscrambler

    rockscrambler rock climber

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    thanks again guys
  9. Kawidad

    Kawidad Long timer

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    That's how my 640 Enduro is set up.
  10. Bullettwo

    Bullettwo Adventurer

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    Thanks Laramie! I have only one question; can I substitute wine for the beer? :photogI'm thinking that margheritas and carburetor work might not be a good match. :D
  11. wrk2surf

    wrk2surf on the gas or brakes

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    its some long story of a guy telling a story the second time.. ior something along those lines...long story short. you answer a quesion just before someone else has or post something that seems new but someone has beaten you to the punch...

    By the way Derek thank you so much for the racing support I will be working on the bike for the next month and will update you!
  12. Sane

    Sane Adventurer

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  13. clicheche

    clicheche Adventurer

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    got the carb completely disassembled, and i took notes as to what seemed to be missing in comparison to the bst-40 bible.

    i have no washer on the needle, aside from the white plastic one. the needle has only one ring for the snap ring to pop into, thus only offering one height.

    i have no float weight on my float, just some clip assembly.
    i have no needle valve, period. space was empty.

    the idle jet is marked at 42.5, will need to increase to 47.5 with the airbox mod and new jet?
    the main jet was marked with, from what i can tell, -782M(some box thing)Y-5
    the o-ring for the main jet looks like there are 3 gouges out of them, though i am not certain. should this o ring be super smooth?

    well there you have it. i have my bike inoperable, though i am nearing some measure of resolution with its fuel delivery system.
    here's hoping i can get this carb in a happier state.

    thanks a boatload for the info in this community everyone. its been cool


    ps: i live at a really high elevation, do i want less gas/more gas to air ratio?
    and furthermore, if i do the airbox mod, (allowing more air intake, nothing huge, just probly 600-800% bigger than the stock snorkel hole) would i want more fuel to air ratio regardless?
  14. theGrinch

    theGrinch SNF Dream Riders

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    If you open the airbox you change the pressure and will need to open the exhaust. What exhaust are you running?
    What bike?

    :freaky

    .
  15. clicheche

    clicheche Adventurer

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    not sure what exhaust i'm running.
    '07 suzuki dr650
  16. ER70S-2

    ER70S-2 Long timer

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    The bible starts off with a KTM carb, also a BST-40. As you've found there are some differences.

    Correct.

    It's hiding in here.
    [​IMG]

    No, stay with the 42.5
    Stock is a 140 and should be stamped on the jet. 150, 160 are common for a jet kit.
    Some one else will have to help here. The main jet doesn't have an o-ring.

    Hang in there, we'll get you through this.

    Technically, you want the same ratio. Since we have less air at altitude, we need smaller jets.
    How high? I live and ride at 6000+ feet. My DR runs better with a 135MJ here.

    Don't worry about your exhaust for now, it's the least of the issues.

    :freaky
  17. clicheche

    clicheche Adventurer

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    just realized today it was a ktm carb!

    noticed the hiding float weight. makes sense
    leaving the fuel screw at 42.5 is fine for idling?
    i noticed the stamp on the nut for the main jet, not on the jet itself. 140 it was.

    the washer i said was for the main jet, was definitely for the jet slide support (white plastic piece), not the jet itself :rofl

    i live @ 3500 feet above sea level.

    i only cut out about 150% more of the initial air intake opening. did you do an air box mod?

    any opinion on the premise of a k&n air filter for more air? would it help with the thinner air at high elevation?

    i threw on one tiny washer against the needle spacer in the carb... hope it won't be too much of an issue. and i drilled out the slide for the slide suction to respond faster to throttle.

    also put together this manual choke, as my cable was seized inside the carb.

    everything's put back together, next up is the direct power to the headlight, and i'm about done for this year. changed the plugs as well.
    the bike only had 12xxxkms on it. the plugs were black. not oily black, but burnt black... sign of being too rich right?

    the largest exhaust hose from the carburetor, is it required to be that long? can i move it out of the way? for more air flow to the air box? i saw a post where someone moved it out of that area at any rate...

    thanks a ton for the response, it gave me the go ahead to just check it out and go ahead. i had problems with it stalling and it had trouble starting from time to time. usually cold starts as usual. we'll see how it goes this year!
  18. clicheche

    clicheche Adventurer

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    what is the petcock vacuum line for?
    reason i ask, is i don't have a line coming out of the top of the carb... this a bad thing?
  19. ER70S-2

    ER70S-2 Long timer

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    :D

    The 42.5 is stamped on the pilot jet. And, yes, the DR is happy with 42.5 in most applications. The fuel screw goes here (and isn't stamped with anything):
    [​IMG]

    The 140 is stamped directly on the jet. :nod

    I think you're talking about this o-ring. Look closely in the pic you can see the bumps that indent the o-ring. I just align the indents with the bumps.
    [​IMG]

    I have to leave the state to get that LOW. :1drink

    I cut a second hole in the top of my airbox, it's about the same size as the snorkel hole (and my snorkel is out).

    I'm not a k&n fan. The k&n flows more air, it also flows more dust.

    You put the washer between the e-clip and the white plastic washer, right? In this gap (and then slid together). Derek will be along in a minute to tell you that you shouldn't have drilled the slide.
    [​IMG]

    Edited to correct terminology:
    Yes, but your <s>choke</s> cold start enrichment plunger was stuck, correct?

    I'm not a Suzuki engineer, I leave those things alone. My second airbox hole is behind that filter.
    [​IMG]

    It's what opens the stock petcock to let gas flow. Does your petcock look exactly like this?
    [​IMG]

    If it does, the little hose goes here:
    [​IMG]

    You're welcome, have fun, ride safe. :beer
  20. clicheche

    clicheche Adventurer

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    wicked thorough! unreal. thanks a trillion.

    so shit. drilled the slide, hopefully it isn't the end of the world. i can always gung it up with some goop or something. why should one not drill it out? aside from the fact that suzuki engineers are much more inclined to know what the hell they're doing than me. :puke1

    i did not place the washer between the white spacer washer and the snap ring. it's on the outside of the white spacer washer. i saw it that way on the bst-40 bible thread and thought that was the way to do it!

    does this mean i'm taking it all apart again? :huh