I think I may have found the "original", or non-compatible with other models, sprocket for the Honda PS50K1.
It is this Ebay auction that shows the right one, including part number 412010-081-000. The picture comes from CMSNL, but the part number cannot be found there for some odd reason.

This needs to be verified still, but I think this would be the right one. (but not for me as I needed 37/38 teeth)

I'm still slowly restoring my Honda PS50K1 and there is some weird sprocket on the rear wheel. It looked like someone bodged some 4-hole sprocket into a 3-hole one and I could not find a replacement for it. So I sent out a bunch of emails to part suppliers and nobody was able to identify it except for one. The company Leertouwer wrote me back, basically saying "No problem, is this the one you are looking for?"

Uh yeah, that's exactly the one I am looking for! So what gives? This sprocket is suitable for the Honda PC50 and the PS50 but for some reason the PC has 4 bolt holes and the PS(K1) has three. While you'd think that with a gearbox you would like to have a bit more stability and strength and thus have 4 bolts. But nay! PS has three holes.

This is so weird, but also pretty cool! So soon I can add more new stuff to my little project:

Just a short message that I've been going through almost every page on CMSNL to dig up usable data. So far I have been adding data for the Honda Z50A and will be slowly adding Z50R and Z50J data as well.

Edit: A and R are processed. J and M is a huge list which will take a bit longer.

A nice video by SmarterEveryDay about how caburetors work!

Dutch manual for Honda PC/PF/PS50 carburetors: https://4-stroke.net/library/workshops-and-how-to-s/739-nl-workshop-carburateur-pf50-pc50.html
Dutch manual for Honda SS/CD50 carburetors: https://4-stroke.net/library/workshops-and-how-to-s/737-workshop-carburateur-ss50.html
And an English artice from oldmanhonda.com about carburetors: https://4-stroke.net/library/workshops-and-how-to-s/706-what-is-a-carburetor.html

Many thanks to Ray Davis from The Benly Page for providing fresh material for the library!!

Parts List for Honda CB72, CB77, CP77, CYP77 (1960-1967)
How to fix your honda (124-305cc) (Low-res), high resolution upon request.
Parts List for Honda C92, CS92, CA92, C95, CS95 and CA95 (1967) (Low-res), high resolution upon request.
Service Manual for Honda CL72
Service Manual for Honda CB77
Service Manual for Honda CB72
Service Manual for Honda CA77
Service Manual for Honda C77
Service Manual for Honda C72
Service Manual for Honda CA72
Service Manual for Honda CL77
Japanese Honda Motorcycle Catalogue (1963) (Low resolution)
Japanese Honda Motorcycle Catalogue (1963) (High resolution)
Parts List for Honda CB92 (1966)
Parts List for Honda CB92/CB95 (1960)
Parts List for Honda CA95
Parts List for Honda CA77
Parts List for Honda CB750 (K0, K1, K2)

And yes, there is even more to come! :D