hey there, if you manage to get the remains of the barrel adjuster out of the mech....fit another one, one off an old SIS mech are better because they are solid steel. (stronger) Then...get a piece of cable inner, cut to about 1-2 inches and poke it through and set the trials gear(normally top one) so that when the adjuster is out at the most that seems safe. YOU DONT HAVETO DO THIS IF U ONLY WANT ONE GEAR - in which case screw it in all the way. by doing this you can change down a few gears, always good when u haveto get about from place to place. hope this helps, ive never known anyone else to do it.