Engine Number vs Year of Manufacture for Commandos

It seems too early to me to have been sorted...but if it's gone this long then there can't be much wrong. What is the mileage ?

The main bearing part number 064118 was used from engine number 211891, so as your one is before that number you may not have the so called Superblend main bearings. Your Commando would have been sold as a 1972 model year but made and dispatched in 1971. On the bright side your engine and cycle parts, by then has had incorporated all of the earlier modifications.

I bought mine new in September 72 and the engine number is 203xxx. My main bearings failed at four thousand miles, which seemed about typical at the time. It is still running fine on the so called 'superblend' bearings that were fitted then 47 years ago.

If yours is running OK then I wouldn't do anything. Norton did retrofit superblend bearings in some already built bikes so it is conceivable that yours has them. The symptoms of failure are a distinctive rumble sound while running. Nothing suddenly fails it just gets louder. If yours has survived as long as it has then I wouldn't worry about it. When I first had mine I didn't apply any rev limit and used the performance, as did most people who owned them. A friend of mine broke the crank on his by exploring the red section on the rev counter. Maybe limiting the revs is the trick to preserve the bearings or they were replaced before you got it.

Ian