Another old question, but who knows may be it was not the seaon for the Toro. :-)
I do for most part agree with Ryan's answer. Clean the Carb, fuel line, and definitely the fuel tank. Replace the fuel with clean fuel. Also, you might develop a vapor lock. Your gas cap should be vented. If it is not, you create a vacuum inside the tank which will prohibit the fuel to leave the tank. Also check the float and the needle valve to make sure that they are working properly. Also make sure that the float bowl is nice and clean...good luck. The proper term is actually hygroscopic : readily taking up and retaining moisture <glycerol is hygroscopic> Sorry had to do it :)