Not really, both Norton and Triumph had 650cc and 750cc dirt bikes in the mid 60s. I do use the dirt bike term loosely. Norton had the P11 (750cc) and Triumph had the T100 (500cc) and TR6 (650cc)

I learned all I need to know about life by killing smart people and eating their brains.
Eat right ,Exercise ,Stay fit, Die Anyway!