Bicycle Mechanics - Broken starnut?

I'm not an experienced bike mechanic, just a rider who does occasional minor work on his own bike, so I apologize in advance for this probably dumb question.

So, I was about to remove my stem today (threadless, 1.125"), to place it a little lower on the steer tube, below one of the spacers.

As I try to unscrew the top cap, I notice that the bolt head keeps turning and turning but won't go out. As I do this, I hear a scratching sound from within the steer tube. I turned it the other way and the same thing happens. The bolt just turns and turns. Doesn't come loose, doesn't tighten up.

is the starnut broken? I'm thinking I may have stripped it by tightening the bolt a bit too hard the last time I replaced my stem.

What are the dangers related to this? Could my stem pop off at some point, while I'm riding? I gave it a few sharp tugs upwards but nothing happened. Would I need a new headset? Could I just take it to a local shop and have them remove it somehow and replace it with a spare starnut?

halp!

I assume you have a metal steer tube, either steel or alloy?

If your stem is properly adjusted then it doesnt matter if your compression cap is even on the bike. The only function of this cap is to set the tension on the headset, the stem has 2 bolts that hold it securely to the steer tube. you are in no danger of your stem coming off unless you have a carbon steertube(ie most carbon forks).

If you have a carbon steer tube I'd be concerned as you should not have a star nut in a carbon fork, you use a compression plug. A star nut will destroy a carbon steer tube.

Can you get the compression cap off of the fork at all? If not turn the bike upside down and take the front wheel off.
Next take a long metal rod(a long screwdriver or the like) and put it through the bottom of the steer tube until it contacts the star nut.
Use a hammer to tap the star nut(you may need some force) so that it goes higher up the steer tube, maybe only needs 1mm
hopefully if you can move it high enough it will bite and you can then unscrew it.


Always lube threaded parts before installing them, especially when they contact like metals(ie steel to steel), to prevent chemical bonding or rust from locking them up.

We just had this problem last week. All the relevant information is here:

http://www.bikeforums.net/showthread.php?620865-stem-top-cap-stripped

It's an alloy steer tube. I can't take the compression cap off at all, since it's held in place by that top bolt. It turns and turns but fails to loosen. Since I heard scratching inside the tube, I assumed that it's the starnut just spinning around, failing to create enough friction to "bite" and allow the bolt to spin independently.

I'll try your suggestion. Thanks!

I wrote my previous post before operator's... I just took a look at this other thread. I'll give this a try...

and I'll make better use of the search next time. :D

Thanks!