A2. 10x1 male spigot down
Links to photos of examples:
1965-66 Harley Davidson M50 replacement
1977 Pacer P14
1977 Negrini Harvard replacement
1977 Cimatti City Bike (when adapter is missing)
1978 Cimatti City Bike (with no 10-12 adapter)
1978 Motron original (extender on tank)
1978 Concord XKE original
1980 Peugeot 103 LVS replacement
1978 Motobecane Model 7 original
1978 Motobecane Model 7 with A2b
This valve fits hundreds of mopeds and mini-cycles. It fits any tank with a 10×1 threaded hole, and with nothing below or near the valve that would interfere.
Motobecane 7 rear tanks have a side wall that is very close to the petcock threaded hole. Modern petcocks are too wide to screw in unless they are first disassembled. Once the handle, face cover, nut, spring and shaft-plate are carefully removed, the bare valve body is small enough to screw into the tank. Then the pieces must be put back in the same order and orientation as they came out.
Cimatti rear tanks have a 10×1 threaded hole, but there is a nearby “wall” that prevents a 10×1 male valve from screwing in, unless the whole gas tank is removed. That requires rear wheel and rear fender removal. To make gas valve installation easy, Cimatti added a screw-in 10-to-12 adaptor piece, and used a 12×1 female type gas valve, with a turnbuckle type nut. Only the nut turns, and the “wall” does not matter. So it is much better to reuse the 10-to-12 adaptor, and use a 12×1 spigot right or down valve instead.