As an owner of one of the fastest Nortons, and a 71 Commando Fastback, I am always interested in that old iron.
Trying to be polite, as they were quite outdated. The orange bike in the pic shows a couple of good features.
The primary chain cover that did not leak, as long as the O ring was installed correctly. The diaphragm clutch was sweet.
Probably copied from a 39 Chev. The triplex primary chain replaced the useless 3/8 single chain.
The drum brake was useless, but the 12 inch Lougheed disc was sweet. The isolastic thing did not work, the rear end flexed, and they were dangerous if ridden hard. The John Player Norton at the 71 IOM made changes to the isolastic system. Traded vibration for better handling. The 360 crank was and is a problem. The electric system was an awfull problem. A four speed gearbox was a bit ancient, but it worked quite well. just needed one more gear. Quaife made a five speed. All that said, folks pay a ton of money for them. My complete list of problems is quite long. But with a lot of British stuff, if you kept the horsepower down, and rode sensibly, they worked okay. My dad had a 16H Norton.