219 is a fairly common chain in kart circles, it's strong enough for most kart drive uses and it's small and light. You can use smaller sprockets and still have enough teeth engaged to avoid over-riding.
The pitch is 0.306 inch, I don't have a clue who picked it or why. Rollers are 0.200. Width between plates is 0.183. Pins are 0.118 dia.
This seems to have been Honda's pet chain for 60's to 70's cam drives. I think the CB77 may use the same length as a 350/400, not sure.