Have read numerous threads on the subject including the Rick Oliver guide which suggests that with the bike running at 5500rpm and the lights on we should see around 14.2v or above at the battery. Lets assume every thing on my NC30 (K) is working well . Is this a realistic figure or is it ok if it only makes 13.5v.
What do you get on yours?

13.5 volts with lights on at 5500 rpm is ok, the battery is being charged while the highest electrical load is connected. If you were to turn off the lights the battery voltage could rise to 14-15 volts but no higher. This is the normal action of the regulator.