What they have in common is they have , nowadays, 865cc. The America and the Speedmaster have a 270 cycle which vibrates less. The Thruxton and the T 100 have 360. The camshafts are different in that the valves are open at different times, with some opening earlier and some others for longer. The Thruxton is bred for racing, but with a seating position not suitable for cruising long distances. But man It goes and it does go around corners. I was lucky enough to be given the shop bike which was a Thruxton when my Speedy was being Dynoed up for the day. Hope that helps.
