Originally Posted by
dabac
+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.
+1 It may well need to be totally removed, and the adjusting mechanism smacked with a rubber-mallet to get it to let go. While a PITA, this is good as it means that stem won't likely come loose while you're riding the bike.