HI Darren,
Start at the beginning. Check if there is fuel in the tank, check if the petcock is open (if there is one of course). Is fuel getting to the pump? Is the pump out putting fuel at the correct pressure and volume? Is fuel getting through the filter? Then you check if the carburetor needle valve is stuck.
If you just want a shortcut, try rapping the carb near the fuel valve with the handle of a screwdriver a few times with it running and see if that helps.
Steve
