Hello, recently started an NC30 project and got around to starting it and it seems to only run on two cylinders.
All four carbs have fuel in the bowls, I have cleaned the jets and diaphragms, there is fuel in there, and checked for spark which there seems to be.
There just is no combustion in the rear cylinders for some reason, I have done everything short of dismantling the carburettors entirely, having made the choke work again as it was seized with oxidisation.
Any help would be great.

Spray easy start, wd40 or petrol into the throats of the carbies while cranking the engine. If it runs then stops after the "fuel" spay stops then at least you know that there is spark and compression but fuel flow is a problem.

AS MAgg said - you need to know you have sparks. I would consider a plug swap too - these bikes do not like getting their plugs too wet.

Swap plugs to track down the problem.
I had same. Swap plugs around and different cylinders would fire.
New plugs fitted and everything fired up. Plugs are not cheap £10 each, and front 2 are tight for space.