[Alex Blair (RIP)]

Stew ....sounds to me like you are out of coil oil....!!
MMMMUUUHahahahahaha...
Sorry Stew ..I couldn't resist it...Sounds like an open coil...Get your ohmeter out and Ohm out your coil....(The two terminals)...You will probably find the coil is open....
Find out why it is open....Over or uinder voltage on the primary side....or defective..broken internal winding...
Try a new coil but check your primary voltage when you get it running...Don't burn it out if your voltage isn't right...correct that at your voltage reg..you may have a coil that isn't right or needs an external resistor...Check it out...Let us know..
Cheers
The old flat head guy..