Pump to carb is a pretty short trip.
Tank to pump leaves a lot of real estate.
One thing that comes to mind is.....did you fill up before it started acting like this? Water in the gas maybe?....
Did you pop the air cleaner and pump the gas to see if it's actually squirting into the carb?
Choke sticking closed?
Vacuum leak anywhere?
Adequate spark?....cracked distributor cap or worn rotor?
The one nice thing about these engines is the simplicity of them. Air, fuel, spark.....If it's not a simple case of you getting a crappy batch of gas then it's gotta be one of those three.