Disassemble and Clean the Fuel Shut-off Valve

What happens here

With the fuel drained, the creator removes the fuel shut-off valve (bung) from the bottom of the fuel tank. He then disassembles the valve, revealing it to be completely blocked with a thick, rubbery, rusty substance. He manually cleans the valve using a screwdriver to clear the obstruction and confirms that fuel can now flow freely through it. He mentions that he keeps spare metal shut-off valves because the original plastic ones, like the one being serviced, are prone to clogging and failure.

Goal: Restore proper function to the fuel shut-off valve.