"turning all the way on"?
If Starter Fluid gets it started for even a moment, it's done it's job.. it confirms that fuel is restricted but the ignition is OK..
Next thing would be to clean the fuel system... question is where to start. You could trace fuel flow and search for the restriction.
First remove the carburetor's fuel hose at the carb and drain some fuel into a container. If fuel flows in a continuous thick and steady stream you know the fuel tank and filters and everything upstream from the carburetor are probably ok..
So, the carburetor itself needs cleaning. It's small passages and tiny jets are easily clogged by little bits of junk.. the residues and varnish left by old, stale gasoline.. maybe rust flakes from the tank too.. or bits of rubber from a hard crumbling fuel line...