Originally Posted by
tricky
...When you thread the bolt in, are you able to tell if the wedge is loose? If not, smack the bolt with a hammer (with some wood inbetween if you want to keep the bolt looking nice) to get it fully loose. It might be stuck to the bottom of the stem just enough to be keeping the stem locked in the steerer.
This is my guess also. Stems like this are locked in place by a wedge-shaped piece of steel which slides on an angled cut at the bottom of the stem. The way to remove the stem is to loosen the stem bolt three or four turns then give the bolt head a good downward smack with a hammer.
At this point you should thread the bolt back into the wedge a few turns and then smack it with a hammer to loosen the wedge. Your rubber mallet may not work, but a dead-blow hammer or a steel hammer should do the job. As mentioned above you can protect the finish on the bolt head with a piece of lumber between the hammer and the bolt.
Brent