I'd say you have a restriction in the fuel line, or in the fuel filter. I would replace the fuel filter and while you have it unhooked, blow air back through the line to flush it out.....be aware that it will spray gas everywhere, when it blows out of the line. I would also clean the carb (meaning completely dissassemble it and clean it)....with it sitting that long, there is bound to be crap in the carb and it could be plugging up a passage, jet, etc.