A diaphragm air leak can cause the symtoms you describe. Are you CERTAIN you got the diaphragm into its grooves and sealed it absolutely air-tight? No rips or tears in the diaphragm fabric?
Clean, "dry," fuel? "Choke" (starting enricher) working o.k.?
I'd imagine you might need to remove, disassemble, and clean-and-adjust the carb, after a long storage interval; don't know how extensive your previous carb cleaning might have been.
The carb may need a bath in industrial-strength carb cleaner.
Last edited by Damocles; 01-31-2011 at 07:29 PM.