anybody know of any place that would have one? I have one on my Schwinn Voyageur s/p but its just a little short (80mm). Ideally I would like one around 100-110.
Would it be unsafe to have a machine shop mill down a regular 1" stem? I have access to a lathe, and someone who knows how to use it.

Thanks folks

EDIT: Swapping out the fork is not an option.

Depends on how thick the aluminum quill is for the machine shop option. I'd check eBay, or the WTB sticky.

I've only found them when I pulled them off of old trash bikes, so no source for NEW ones AFAIK, but if somebody has a lead, please chime in.
I've used a lathe but I think you'll find there are limiting factors: if you can clamp the TOP of the stem in the chuck, it's easier to cut right down to the end, but you will have the bar-clamp spinning around in such a way that access is limited up high (watch out for your fingers!). And if you clamp it on the bottom, you still have that bar-clamp threatening your hands, plus you can't cut down the portion that's in the chuck (I ground mine with a wheel to finish the bottom off). Good luck to ya!

Is it possible to use a different headset that takes a normal size stem?

I think patience and ebay are the best solutions. I bought one on ebay, but of course they're not terribly common. The one I bought wasn't even specified .833, but I could tell by the ebay photo it was likely a .833 by the way the quill was sharply necked down. I don't think the seller even realized it was .833, there was certainly no mention of it in the ad. For the $6 or so that I paid for it, I was willing to take the chance on it. It was an unusually tall stem, just what I was looking for. Good luck-

No, I believe the fork's inner diameter is the problem.

No, it's the inside diameter of the steerer tube that mandates the .833" stem. The headsets are standard 1" headsets, with the only difference being that the lock nut has a smaller inside diameter at the top so it fits snugly around the .833" quill.

wellbiked has it right, you just need to retain the top nut. You will also need the crownrace that fits your fork's crown, or have that milled to 26.4 if it's not already.
Edit, of course that's correct as stated below, I shouldn't try to remember details wihout holding the parts in my hands, too many things swirl together.

Actually it's just the lock nut at the very top that's sized to fit the .833" stem, the threaded part of the lock nut and also the threaded race is the same as a standard ISO 1" headset. In other words, the outside diameter of the steerer tube is standard 1" stuff, including the threads, it's just the inside diameter of the tube that's smaller, and therefore the stem's quill has to be. The idea was to have a thicker-walled steerer tube, but at the expense of a smaller diameter quill-

https://www.bikeworldusa.com/index.ph...70d65900622b9d

Has two 21.1 stems, tall and regular. Doesn't list the extension. Maybe you can estimate it from the photos.
Also, aren't 'BMX' the same 21.1?

[edit] oop i guess the Voyageur is a road bike that should have a nice Alu stem; these appear to be maybe cheapish steel stems for middleweights w/ upright bars /

Yeah, the other problem with those is that they have a 22.2mm clamp diameter (for steel handlebars), 25.4mm is likely what's needed for FlatFender's Voyageur-

I'd keep you're eye on cheap Japanese bikes, I have had two bikes with .833 stems, and one of the stems is actually quite nice.

Do you need any significant amount of rise? I have a .833 stem that's 110 or 120, but it's pretty steeply angled- down, that is.