A wonderful crazy Combat mentor of mine in NYC city, on realizing his non Whitworth tools didn't fit much, filed each nut and bolt to fit his tools on hand. Me on the other hand fogged over looking at the repair sections of manual thinking that's for experts I'll just ride and top off fluilds and replace simple stuff like rings, HA little did I know I would one day ignore manual, especially torque values and fluid levels and type of fluids. Took me about a decade to get familiar the hard way.
Nortons need constant attention, then almost as constant maintenance, with punctuated major over hauls. Besides tools there are a number of little items to keep on hand, like clutch locator circlips and oil pump nipples and TS cover gaskets.
Can't forget the electric bullets or blade terminals and electrical wiring tools, like solder and shrink wrap and crimpers. Dental picks straight, curved and 90's really helpful as well as strong magnet to suck out clutch plates.