How to clean the fuel valve on GXV120 carburetor?

Any ideas how to unplug a valve on a Honda GX carburetor, which was left too long with old ethanol gas in it, and has plugged solid? Soaking it for serveral days in carb cleaner, pumping cleaner into the hose nipple with a oil gun, and repeatedly blowing it out with compressed air has accomplished nothing. The valve is riveted together, so I don't want to try taking it apart except as a last resort.