It looks like it's held in place with an e-clip. Use a small flathead screwdriver between the shaft and the clip to jimmy it off, then the gear should slide off.

Can't tell for sure with all the dirt on it, but it could be a snap ring. It doesn't look like it uses the same e-clip as the other gear to the left is using.

Yes, I’ve already removed that one, I mean the smaller broken gear.

Not a snap ring, unfortunately. That’s just the top of the brass fastener, it has a tubular body that passes through the gear. The second picture shows how the other side of the fastener.

I didn't see the second pic. That looks like it was peened on so the gear is probably on a flanged axle that would not come off unless you removed the axle from the bracket.

You might be able to get it off by using a hammer and a punch to try and narrow the side in the second pic so it will fit through the hole. Then have to peen it back on later. Or you could grind/file off the end sticking out in the second picture, but would likely have to replace that axle pin afterwards.

What does that gear do? It is too small to be transmitting a ton of torque, so I am assuming it is to transmit the speed or distance that has been traveled.

I would probably replace that gear with a 3D printed one because I think you will have a hard time finding a replacement.

Excellent, thank you. I will try the hammer and punch.

Ah, okay. I will agree with the person who said it looks like a peened part - pin and hammer, or still it out

This might work:

https://www.bicycleheaven.org/products/bicycle-speedometer-drive-stewart-warner-vintage-nos

Otherwise looks like its permanent and you'd need to hammer it out.

Is that nylon? You could have a replacement 3D printed.

I just made a similar gear out of brass, using a milling machine and a dividing head.

The problem with this gear is that you are unlikely to find a replacement; it looks like a 14.5 degree pressure angle and most gear shops are set up for 20 degrees or higher. Ther's nothing available off the shelf. I could make this gear, but it would be a $450 gear.

It drives the speedo cable. It would be cheaper to grab a display and proximity sensor to count revolutions of the wheel than to build this gear. It has to be ridiculously tall-toothed to register in the perforated disc- looks like a 14.5 degree pressure angle and no longer a standard gear profile. Pretty easy to just bore a flat disc of delrin to the same OD and bandsaw&file the teeth- it doesn't need to be perfect.

Are you trying to restore the bike with all-original parts, or do you just want a functional speedometer/tach? If you're just looking for a speedometer/tach, then get a cheap bicycle tach with a magnet you stick on a spoke.

Drill a 1/8" hole down the riveted end. Squish the peened-out wings of the rivet together with vise grips. Punch it out. Take the gear to a small machine shop and ask for a flat disc of delrin bored and machined to the same OD. Trace the existing gear onto a piece of maskiing tape, slap that on your disc and bandsaw and file the profile.

It's a 9 tooth gear with what looks like a 14.5 degree pressure angle. A dividing head (and I'd guess module 3 cutter) will get you very close if you have a milling machine. You don't even need to have dividing plates because with 9 teeth your divisions are bang on 40 degrees apart- you could just paste on a printed sticker of a protarctor and work to its lines. http://www.banggood.com/8pcs-Module-3-PA14_5-Bore22mm-1-8-HSS-Involute-Gear-Milling-Cutter-p-1012467.html

Looks like someone purchased it, but I get the idea. This was vey helpful, thank you.

Thanks, got the gear out and working on replacing it, but this will come it handy if it fails.

I’d prefer all original, but alternatives won’t kill me. Thank you, this is a nice workable option.

Oof, that’s probably 10 times what the bike cost brand new. I’m currently carving out a replacement gear with my dremel. Fingers crossed.

Thanks, I don’t have a printer, but I’ll keep this open as an option.

Ooo get the gear off, 3D scan it, and print replacements!

Edit: if it's just speed, might make more sense to not bother and just grab some Bluetooth speed/cadence sensors instead they're cheap.