hey, i'm fixing a vintage bike (80's bianchi) and I wanted to move up a little bit the stem. Unscrewed the top bolt and wasn't able to move it up or down. So i hit the stem from below with a hammer a couple of times, I couldn't move it too much if any at all but I think I did move the top compressor (i don't know how it is called) a little bit upwards (I think there is a space where didn't use to). The point is that now if I put back the top bolt on the stem I can't tighten it, it just moves freely (the bolt). And still can't move the stem up, down or free from the fork.
Is this a seized stem? If it is how do i fix it? I found that to fix a seized quill stem you screw the top bolt and hit it with a hammer, but as I can't screw the bolt I don't know if it would help.
Please answer shortly, I've been fixing the bike for months and can't see the moment to ride it.
I also need to unscrew the bolt under the handle bars to change the angle, but it seems seized af. Please any help is welcome.

The stem bolt extends through the stem to a wedge at the bottom. Tightening the bolt presses the wedge against the steer tube and holds the stem in place. Standard practice is to loosen the stem bolt slightly, then strike it from the top with a hammer (a soft face or wooden block on the bolt head prevents damage to the bolt head) to loosen the wedge at the bottom of the stem, after which the stem should come free. From your description, it seems you have disengaged the stem bolt from the wedge, and the wedge is still jammed in place holding the stem. You will want to re-engage the stem bolt with the wedge to be able to knock the wedge loose.

Penetrating oil on both the stem and wedge from below should help, as well as on the bar binder if that seems seized as well.

thanks men, but how do I re-engage the stem bolt?

The simplest way to LOOSEN a (functional) quill stem is to undo the bolt a couple of turns and then tap it down to release the wedge at the bottom.
A little wiggling and turning on top of that is usually enough to free up a functioning stem.
To loosen a seized stem may finally come down to careful application of brute force, which is hard to provide on-line.
Some steerer tubes have a narrower section at the bottom. If the wedge has fetched up as this as the bolt is tightened, removal can be quite a challenge. The wedge can't be knocked up, b/c the stem is in the way, and the narrowing of the steerer below. Penetrating oil, wiggling and twisting etc is pretty much all your options.
Worst case, you've got corrosion between the stem and the steerer tube. This means there's a fairly big surface involved, which can je really difficult to overcome.
When you say you hammered on the stem from below, how did you do that?
Did you insert something through the fork crown, or did you simply hit the stem on the underside of the forward protrusion?

Put the stem bolt back and screw it clockwise so that it re-enters the threaded hole. When it starts to tighten up, stop and back it out a couple of turns and proceed to whack it with a hammer as advised earlier. Here is an article with some diagrams which may clarify what you are doing: Hands Up (Or Down)! Adjusting Handlebar Stem Height on Your Bicycle There is a cross-section view near the bottom which shows what the wedge looks like.

If the wege has come off the stem binder bolt and is too far down to be re-engaged by the stem binder bolt you might try this. Remove the front wheel. look at the underside of the front fork. Is there a bar between the front and back of the fork? If not, remove the front brake from the fork and push a wood dowel or very long bolt up throught the bottom of the fork and use that dowel or bolt to push the wedge back up to the stem binder bolt which you then turn to engage the threads of the wedge.

I've had luck loosening a stuck stem by leaving the bike upside down with the stem over a shallow tray and then pourin some penetrating oil or even regular oil into the fork. leave that work overnight. I strap the handle bar to a picnic table with one strap at eiter end of the bar and then use the frame of the bicke as the lever. A lot of time applying a steady force then slackening off the pressure and then apply pressure suddenly again will break a stuck stem loose. Tapping the stem vigourously whilst apply pressure can also help. A second person doing the tapping really helps.

Another thing that can help is to empty a Co2 cartridge onto the base of the stem just above where it goes into the headset whilst being careful not to get the headset too. That might shrink the stem enough for it to break loose.

Good luck and cheers

I unscrewed the top top bolt and then hit what would be the separate stem in a threadless stem from below. In the top part of the bike (I don't know how to explain it better). I tried to move the stem free from the wheel and it's still working together.

The problem is that when I put the stem bolt and try to screw it the bolt just spins in place without any opposing force. I mean I can't screw it in so...

Thanks for the replies I'll try some wd-40 to get it loosen now, it's the closest to penetrating oil that i have at hand.

Corrosion and Rust mingle aluminum and steel oxides .

I think I got it fixed. Thanks for the replies and all the help!
I got the bike upside down, put wd-40 on the fork and got it loosen. Not very easily I could get the stem out but the wedge was still inside and because I couldn't screw the bolt onto the wedge from the stem I removed the stem and screw the bolt inside the wedge and got it out. Reasembled it and I think it is good now, will have to test it in the streets.
Thanks again for the replies and help.

Very carefully.

You'll have to line up the bolt with the hole in the wedge. Fortunately, if the wedge is stuck, it won't have moved out of position so you'll just have to feel around until it engages.

Grease the stem, wedge and bolt and check/regrease them regularly so that this does not happen again; seat post too.

Great thread thanks everyone. My problem was also a bianchi and the hammer trick worked great i suggest a hard plastic mallet. Now i also had stopped a project because of similar issues but the bolt was completely loose and the nut at the bottom but wouldnt fall out of the way to tap directly on the quill stem that was completely seized. Any tips on this one.

If the wedge doesn't drop out the bottom of the fork, it's usually because the steerer tube is butted, that is, the steerer tube has a thicker wall at the bottom than the top. There's a variety of ways around this, but they usually involve a sturdy bench vise, penetrating oil, and selective application of leverage.

These applications are the ones i dont know. Do you recommend any video tutorial on this i guess i could try my luck searching myself before i loose it on the bike and trash it.

Do a YouTube search on RJ The Bike Guy and he has some great tutorials on removing even the most stubborn stems.