Could be Sticky
Just replace the sticking needle/seat and insure fresh gas with a little Stabil, its
a carb problem, so open it up slowly as the diaphram can stick then you'll need a kit.
Get a pop-off tester and leak down test it after re-assembly and re-install it.
There is more often than not a problem inside a carbureator, typically, those problems are water sitting in the carbs rusting up stuff, needle and seat valves that are stuck shut, diaphrams that are stiff old and hard, sometimes vulcanized ( glued ) to the diaphram cover plates so they can barely move inward to open the needle valves when necessary, or just partially open the needle valve which reduces fuel flow, gasoline/oil varnished internal carb parts, clogged internal filters, bad fuel pump diaphrams, ect.ect.ect.
Then to add to the list, water in the bottom of the gas tank, or a gooey mess of hardened pre-mix oil that separated from the gasoline, a clogged up fuel selector valve, rotten fuel lines and last but not least, the wrong style inline fuel filter. The one small fuel pump that feeds one or two thirsty 720 carbs cannot put up with any restrictions caused by the wrong style inline fuel filter. Fuel should flow easily with 3-5 psi route pressure. Hope this helps.
Bills86e