A25. 14x1 female spigot down
Links to photos of examples:
This spigot down valve was original on 1979-81 Honda NA50 Express II. It also replaces the original spigot left on Honda NC50 Express, and the original spigot right on Yamaha QT50 Yamahopper.
Honda Design: Note that the little arrow on the handle points opposite to the handle. So off is arrow left (handle right), on is arrow up (handle down), reserve is arrow down (handle up).
This valve has a 6.0mm spigot, for 3/16″ (4.8mm) hose.