Originally Posted by
HillRider
... You loosen the hex bolt whose head faces the drive side of the bike several turns and push in on it's head. That pops out the disk on the other side that has teeth that mate with teeth on the stem itself. Adjust the angle, push the nds disk back in to reengage the teeth and tighten the hex bolt TIGHT.
+1 on that. The two adjustable ones I've encountered worked that way. The teeth engagement is quite deep, so you really need to loosen the bolt several turns to get the stem moving. It's not something you can undo a little and get it to slide.