It should run on gravity feed. Check to make sure the needle is not stuck in the seat inside the carburetor. I use to take compressed air and blow it in the fuel line to get the needle to drop and allow fuel flow. You may want to limit air pressure though. Not sure is 100psi is a good idea.
As always though check for spark too.
I'll second on the pressure. Floats do collapse when you pressurize a carburetor. Don't ask, I won't tell.
Gravity feed will get the job done. If you aren't getting fuel that way, I'd say a new needle and seat valve would be in order.
I always give the engine a little squirt of fuel into the manifold/air horn when it needs to start after years of sitting. If it fires a few times and quits, you know compression is close to good, spark is probably okay, and any problems exist in the carburetor or fuel system.