Mountain Biking - Stem/Quill Size and stripped bolt

I have an old Diamond Back '93 or '94 I believe it is an Axis. It has a Zoom Sport stem and I am trying to either raise it or replace it, however the bolt is stripped.

If I were to replace it, does anyone know off hand what size I would need - 1" or 1 1/8"?

Any tips for getting the stripped bolt out?

Attached is a picture. For obvious reasons I would also like to get a new lock nut and front brake cable holder.

Thanks for your time.

Sometimes an SAE Allen key will be just a bit bigger than the equivalent metric Allen key. Use this to get enough bite to loosen the quill bolt. If not, and if the bolt isn't countersunk (flush) you might try something like those left handed destructive removal sockets you can get from craftsman or harbor freight.

Thanks for the quick reply. Any idea from the make/model what size stem it is?

If replacing headset, you will know size and delve into the joys of stack height and vintage parts. Enjoy , and look at the bearing races

If replacing headset, you will know size and delve into the joys of stack height and vintage parts. Enjoy , and look at the bearing races

I don't think I will be replacing the headset, just the lock nut and cable brake stopper. I'd just like to know the size now, so I can order the parts while still trying to get the stripped bolt out.

Thanks for the quick reply. Any idea from the make/model what size stem it is?

Zoom stems came in 1", 1 1/8" and 1 1/4" so I can't necessarily tell by make alone. Looks like a 1 1/8" to me, but I'd find someone to confirm. If you can't get a 32mm headset wrench on the locknut, it's larger than 1".