You said you cleaned and checked the carb and changed the air and oil filter, did you change the oil also? If so how much was there? If you did change the oil did the stuff you drained out look and smell like it might have had gas in it? Over filling the oil and/or a stuck float valve can lead to the issues you had, if by some chance you hydrostatically locked up the engine you can clear it by removing the spark plug(s) and cranking over the engine but watch out for all the mess that will come out of the spark plug holes. Head gasket(s) are fairly easy to replace.
Tom