Even if there is no fuel, it should catch on a bit with starter help spray in the carb. If it cranks as normal, and doesn't do anything at all (not even for a little bit) with spray help, there is an ignition problem..

I had problems with my starter in the past. It would crank, quite slowly, but catch on. Untill one day, when it wouldn't anymore, no matter what I did. Only after I replaced the starter for a new one, I learned the normal speed in which it should crank; quite a lot more powerfull then what I was used to. Turnt out my old starter had been dying for a long time, but I didn't know, 'cause I never heared it start with a good working starter! LOL.

Good luck! I hope it's as simple as the fuel!