Can't get engine to run without injecting gas into carberators. Prework: Pumped all gas out of tank, added new gas. By-passed P-valve/auto shutoff to eliminate it. Installed new plugs. Injected sea foam carb cleaner into line feeding two carb and lightly pushed air thru to see it come out into carbs to see path clear. When trying start with choke, nothing but slight firing it can't sustain.. Pour gas into carbs and starts easy when twisting grip toward full throttle, with grip twist reving engine until fuel used. Without more gas engine starts to die and carbs sound like they are sucking lots of air as motor goes into shutdown. Keep pouring gas in and it can run forever. I know fuel pump working because U can watch it pump into a catch container as long as I fuel carbs. History: Carbs redone in 2004 after sat with fuel in it since 1997 and was not driven during those years. Had only 99 miles at that time. Drove 5,000 miles. In 2011 I quit riding except rides to keep it running. Last time rode was spring/summer 2012. Put up with fuel stabilizer and not driven since. Can anyone suggest the most likely problem?