[Johnson] Ranger/Valiant with Xtals

[Fabio Liberatori]

     Hello,
              I recently bought two 7.143 MHz xtals for 14.286 MHz use 
in my Johnson transmitters, but no luck...
Both do not oscillate, even if they are of new production (fitted 
into the old FT-243 case).
I checked the correct position on the xtal socket, of course...
I did any other attempt I was able to imagine...  Cleaning contacts, 
changing position, and so on...).

Is my 7.143 xtal frequency choice  wrong for 20 meters use ?
Do I need actually 14.286 MHz xtals ?

Does anybody use Rangers and Valiants with xtals here on this reflector ?

     Any suggestion will be very appreciated,

                Fabio, I0LBE