Small Engines (Lawn Mowers, etc.): lawnmower, internal passages, priming

Question
I have a craftsman 4.5 HP lawnmower that I bought last year, May 2003.  I recently tried to use it for the first time this year, 2004.  When I tried to start it, it ran for about 5 seconds then stopped.  I then read over the owner's manual and made the changes that it suggested.  Which were change the oil, replace the gas and change the air filter.  Since then I've tried to use it once again and the same thing happened.  Do you have any suggestions on what could be wrong with this practically brand new mower?

Answer
If it will only run for a few seconds after priming or on choke (depending on your model), the carburetor needs to be cleaned thoroughly including pushing a piece of tag wire through all of the internal passages...especially if you left fuel in it over the winter.  Hope this helps.