A3. 10x1 male spigot back
Links to photos of examples:
1977 Intramotor-Gloria Scout
1977 Malaguti Commuter original
1978 Malaguti Commuter original
1978 Baretta 38 (and 22) original
1978 Baretta Magnum (top tank)
1978 Yankee Peddler original
1979 Cosmo Colt original
1979 Motobecane 50V original
1977 MB 50V orig made by Quiet
1980 Cosmo Colt 3 original
1985 Safari 300MT Turbo replacement
1987 Motomarina Raven (monotube)
A3 or A4 for Motobecane: 1970’s sheet-frame Motobecanes use a A3 type vertical valve, but not in a vertical orientation. Instead it is almost horizontal, at about 70 degrees from vertical. So a spigot-back valve fuel hose goes down, not back. An A4 10 x 1 spigot-left is a better replacement choice. With A3 the fuel hose goes down first, and then slightly uphill before it curves down into the Gurtner carburetor. With A4 the fuel hose goes forward first, and then slightly down hill before curving down to the carb. The A4 allows the fuel hose to be empty when the tank is empty. The A3 with a U-shape hose routing would trap some liquid, just like under a sink drain. Then the bike would have to be leaned to the right to empty the fuel hose completely.
Side cover grinding: With all replacement petcocks the Motobecane 50 or 40 left side cover must be modified. The front side of the petcock slot must be have about 1/8″ (3 mm) cut off. See the above photo.