Originally Posted by
eacolin
Thanks for the tips guys. Hitting upwards with a hammer, with wood between stem and hammer, didn't help, unfortunately. Is there any sort of jig for me to get better leverage when trying to push the stem out from below?
Sorry, i advised you to try to skate by using a shortcut earlier.
The secret to effective hammering is an anvil or a dolly ( a sort of hand held mini-anvil) to add to the inertia of the hammered part and concentrate the force. If you have a bench vise, open the jaws to just clear the stem and have a friend hold the bike upside down with the headset laying across the jaws. Then drive the stem down (after loosening it -doh!") using a wood block set against the base of the extension. With the headset and fork immobile the stem will move. Once it's popped free,
slowly work ir loose.
Note overly working jammed aluminum parts can heat them to where they're softer and cause gaulling which jams them tighter yet. That might be what happened earlier. Adding penetrating, or cutting oil helps prevent them from seizing.