I need help with this. I'm converting it to a single speed. It's a 2004 GT Timberline Ltd. I want to remove the stem (adjustable... Lame) and replace it. It says it's a 1 1/8 threadless sealed mechanism. I hope I attached the pictures correctly. Any help on how to remove it correctly and replace it?

That isn't a 1 1/8" threadless system. That's a threaded headset and steerer, although it may still be a 1 1/8" steerer.

There should be an allen-headed bolt recessed into the top of the stem. It may be under some sort of cover. Loosen that until the stem moves (you don't need to remove it all the way).

Thanks. Going to check it out now.

The odds are you will loosen the allen headed bolt but it won't come loose; that's because there is an expander wedge at the bottom end of the stem and it's, well, wedged in there. Loosen the allen-headed bolt a couple of turns and then whack the top of the stem with a wooden or plastic mallet and the stem will come loose.

Before you install the new stem be sure to grease the bolt threads, expander wedge and the part of the stem which goes into the steerer to help avoid it corroding and freezing into place.

Also make sure that you don't put the stem all the way to the bottom of the steerer opening, which is tapered. Expanding the wedge into the tapered section invites sudden, unexpected loosening of the stem. Having the bars come loose is only funny in the movies. Scroll down this page for a diagram and more details:https://www.sheldonbrown.com/handsup....-compatibility

Got it out with three turns of the Allen wrench. Going to get a stem adapter. Thanks for the help.