You have a line running from the muffler to the fuel tank vent, right ?

Start the engine up, and get it running full blast. Pull the fuel line off the
carb and see if you have a good stream of fuel coming out. The engine
will quit after a couple seconds....but you should have plenty of fuel
coming out.

Sometimes on a upright carb set-up, you have to set the carb really rich.
The carb is way higher than the tank....it will tend to lean out on you when
you take off....it may seem OK on the ground, but it's not. You must have
good tank pressure on an upright engine.

FBD.