Carby Small screw with spring on side of carb

Discussion in '2-Stroke Engines' started by Mister R, Apr 9, 2007.

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  1. Mister R

    Mister R Guest

    Got my bike fired up for the first time today. Runs great, but the little screw on the left side of the carb (the one with the spring) vibrated out and is gone forever. It still runs good, but I know it serves a function and should be replaced. This is the idle adjuster, right? Does anyone know the screw size and thread size that fits so I can just hop on into the hardware store and go straight for what I need? Thanks!

  2. Guest

    Guest Guest

    I don't know the screw size, maybe that'sdax will chime in here...

    I would, however, plug the hole with something temporary at least so you aren't running the engine sucking air in through the screw hole.
  3. srdavo

    srdavo Active Member

    yeah...thats the idle screw. I'm not sure what mm. bolt , but it's the same size as the two that hold the float bowl.
    here's a pick of what your missing bolt looks like. ..the black one


    If you just get a bolt to plug the hole, you can still adjust your idle speed where the throttle cable enters the carb.
  4. gone_fishin

    gone_fishin Guest

    anybody else noticing how completely cool srdavo's tech/mech posts are?

    your contribution to MBc is greatly appreciated 8)
  5. azbill

    azbill Active Member

    that's why he's SIR Davo haha :p :p

    I am old school and don't give or take respect lightly (and I still hate being called Mr.! )
  6. Mister R

    Mister R Guest

    Amen my motoring bruthas. Sir Davo is most definitely an asset to the community. Also, gotta give some kudos to Bird and Tom as their installation instructions made things alot easier for me.
  7. thatsdax

    thatsdax Guest


    Do not run your motor with this screw missing. It will cause a lean condition and burn your motor up.. Go to and get a new screw with spring. Thanks..Enjoy the ride..
  8. srdavo

    srdavo Active Member

    thanks, guys, for the kind words.

    and a special thanks to dax for having the parts.......
    and getting us back on topic! :lol: :p
  9. Mister R

    Mister R Guest

    If I found the proper thread size wouldn't a regular screw work? I know that it looks tapered at one end, but isn't the whole idea to keep the air out? Or would that keep too much air out and make it run too rich? Why is it smaller at the end? I'm new to all of this so please be patient with me. I guess I just don't want to spend $4.95 on another screw and wait a week for it to arrive only to have it vibrate out and be lost down a city sewer somewhere if I can just buy a handful from the hardware store. Thanks!
  10. Dockspa1

    Dockspa1 Guest

    Mr R
    Thats weird, most carbs on other machines won't run at all with out the mix screw. It is a taper because it enters the jet hole to allow for lean or rich mixture.
    Hope you find one.
  11. gone_fishin

    gone_fishin Guest

    the screw is ONLY for idle speed. it acts on the angled slot on the bottom of the slide to raise or lower it.

    in a pinch, you could use the rightsized screw to block the hole from airleak. then, use the cable-housing adjuster on top of the carb to adjust the idle.
  12. Guest

    Guest Guest

    Right on augi! Plug the hole with a plastic cap, piece of wooden dowel, ect (make sure it can't get sucked it) and adjust the idle with the cable housing adjuster.

    Or go to Home Depot and buy the right metric screw.

    Or buy one from dax and put some thread locker (or nail polish if you have a house full of girls like I do) on the threads.
  13. gone_fishin

    gone_fishin Guest

    in my case, i'm constantly adjusting idle "on the fly" to match conditions.

    so, locking the idle screw might not be the best idea unless you've got a setting that works all the time.

    try pulling the spring a bit longer, making for more holding-power. at first mine would vibrate out pretty fast, but after lengthening the spring i've had not one problem with it.

    tip: if you "make" your own idle-screw, file/grind a bevel onto the end of it to match the angled slot on the slide. this will make for smoother adjusting.

    another tip: if the screw insists on vibrating loose despite your best efforts, use some wire to make a "safety harness", wrap a loop around the head of the screw (include one turn of the spring in this loop) & the other end around something solid...if it does come all the way out, screw & spring'll be dangling there waiting for you to figure it out.
  14. Guest

    Guest Guest

    Here's another "old timer" trick- use a short piece of very light fishing line. Take the screw out, put the line in about 1/2 way and put the screw back in. (it's not as hard as it may seem). This acts as a type of loctite, but allows you to turn the screw. It won't ever vibrate out again.
  15. Mister R

    Mister R Guest

    Thanks for all the handy tips guys. I found the right size screw at the hardware store today. It runs a whole lot better. I also found a thicker spring. I put it on and went around the neighborhood a buncha times and it hasn't budged. Seems good to go. Thanks again!