As I've previously mentioned my NC30 is not starting I'm trying to get it started but am not a mechanic just looking to learn. It has been mentioned it probably carbs as I have got good spark so I have taken the tank off this evening and the vacuum pipe (small one) was split on the tank end. Would this stop the vehicle from starting? Any help will be greatly received.

If its split enough so it doesn't create a seal then yes

Where can you buy replacements online? Can I just trim the split end off and reconnect or is it better to replace.

well trim it so you can see if the bike starts then if you want to get a new pipe rick oliver is the man to get bits from,

yes, that could stop it starting. my vacuum line was misrouted once and when the bike warmed up it would cut out due to lack of fuel and refuse to re-start

Well I can rule out this pipe, just trimmed and put everything back as it was and still no life! Also found there is no sub air filter in. I guess it's back to trying to get the carbs off.

Have you put the pipe back on the correct spigot on the tap.

Yea pretty sure I have.

So heres what I think you should do. Disconnect the tank from the carbs .. Both the vacuum and the main supply. Suck on the vqcuum and see if petrol runs out the main line. .. ie make sure petrol is getting into the carbs. If this is good then remove a spark plug lead and put a screw driver in it and hold the screw driver very close to the frame while you crank the motor... like a 1mm gap.... If you see a spark you have spark ... Do this for all spark plug leads. . If you have spark on all four leads then. The only thing it can be is a problem / dirt in the carbs. Just for fun squirt something like petrol or sure start down the carbs while cranking the motor. .. It should try to start..strip and clean the carbs..... and probably before you do all of that make sure you have enough fuel in the tank