I'd venture to say that by letting the tank run dry you put a lot of crud into the fuel system. I would pull the tank and flush it out and blow out the fuel line from the tank to the fuel pump. Replace any and all fuel filters and after you get it running again you might have to replace them a couple of more times.
Rebuilding the carbs is not that involved as long as they are cleaned thoroughly and all of the passages are blown out with compressed air.
Tuning them is another story as they should be balanced.