Went for a bimble with my mate yesterday who has just purchased a NC30 in what I must say is very good condition and after a fuel stop he hit the starter button and all we got was a clicking noise from the Starter solenoid located behind the offside rear seat unit, I tried the button and it fired straight up . Now having tried it a few times when he got home it was intermittent sometimes it fired straight up sometimes just clicking. Now I now the battery is fine as it is a brand new motobatt, so I have concluded it is either a Solenoid problem or the starter its self. I have had a simialr issue on a CB500 and the starter on that was simply filthy inside when I took the top off and after a clean worked great. As I do not have my workshop manual to hand is the Starter motor on the NC30 rebuildable or a sealed unit?? as it would be worth telling him to give it a good clean and check over before spending on a new one.

First thing I'd do is bypass the solenoid to see if the motor spins reliably.
You'll need a jump lead, clip one end to the Battery +ve terminal, and touch the other end to the starter motor terminal.
If it doesn't, then it's the motor.
If it spins over consistently, then you have dodgy solenoid contacts, or a duff connection on one of the leads.

Check all the connections (Battery terminal to lead, lead to solenoid input terminal, solenoid output terminal to motor lead, and motor lead to motor terminal).
Take each one off and clean if necessary, using a fine grit (>400) wet-and-dry paper, emery cloth, or green Scotchbrite.
Clean the terminal tab and the part it contacts and reconnect.
If they're all OK, then the solenoid is at fault, not sure if it's strippable or not.
If it is, then you can clean the contacts inside in the same way.