Here's my tale of woe: I found that my front shifter wasn't working at all - I think I must have accidentally twisted the barrel carrying my bike upstairs - so I tried loosening the barrel to fix it.
Not my first mistake, but a mistake nonetheless!
A small pin, roughly 2mm in length and shaped vaguely like a cotter pin (except symmetric) fell out of the barrel adjuster on my down tube. (I have STI 105 shifters.) Looking at the right side barrel, it was probably wedged in next to the rotating part.
Bike Nashbar AL-1 ,Raligh M50 , Schwinn Traveler , and others
did you find a small spring than goes over the barrel ? and the two parts goes into the plastic adjuster. you will have to remove the cable from the front dérailleur, I think you might need to replace the barrel adjuster parts which you can buy at your lbs for around $5. strew the adjuster back into it's post back off by one turn run the cable though it, reconnect it to the dérailleur and adjust the tension so it will shift again using the adjustment barrel.
2010 Motobecane Immortal Force 90' Trek 1400; 90' Trek 850; 06' Trek 520; 01 Iron Horse Victory
If you are unable to loosen the barrel adjuster the threads are probably full of debris or corrosion. If possible, get some penetrating oil in there and turn it looser and tighter then apply triflow or another proper lubricant or even better get some grease onto the threads. Never done that before so not sure if you can completly unscrew them to access the treads.
I was referring to the small silver clip that juts out of the barrel. You can see part of it in the gap as well. I don't know if it was meant to be removed when the bike was assembled, because it's not held in very well!
I got it back in and the bike is shifting. Thanks!