Frozed Stem

Is the bolt stuck or is it the stem itself? If it is the bolt, then you need to spray penetrating oil or WD40(curse word in this forum), into the steerer tube from the bottom. Just invert the bike, remove the front wheel and spray away, and then let it sit overnight. If this does not work, you'll have to drill out the head of the bolt and go from there.

If the bolt unscrews but you cannot pull the stem out of the steerer tube, just unscrew the bolt partway and then whack it with a hammer. You can put a peice of wood over it if you don't want to mar the finish when you hit it.

If neither of these work, then it sounds like it is time to buy a new bike, or a box that will allow you to put the bike in it without removing the handle bars.

I　had the same problem recently. I sprayed a rust remover into the headtube, then put a screwdriver into the hole in the underside of the fork; you should be able to reach the frozen part of the "wedge" of the quill stem from underneath like this, through the hole in the bottom part of the headtube. Then tap it with a hammer. An alternative method is to use the bolt from the stem: take it out completely, then use it like how I described using the screwdriver, from the underside, and thread it into the bottom wedge, then tap with a hammer. If you use a screwdriver, you may hav eto experiment to see what type (philips or flat) and size fits through the hole in the underside of the fork. Good luck!

what materials do you think you are working with? painted chromoly stem?painted aluminum stem? polished aluminum stem? titanium stem? aluminum wedge?

ammonia is a standard and effective method to break down the corrosion that develops around/between stuck aluminum parts... i have seen this method work overnite, i have also seen it dripped on stuck parts for weeks before they were freed up...

soft wood sandwich-ing the bare crown area of the fork with the brake removed in a big vise may be better than a front wheel for leverage... this used to be very safe, but with todays carbon forks i would be gentle with it...

also i have never tapped on the bottom of the wedge, in doing so i would be concerned about the steerer tube buldging...

good luck