Small Engines (Lawn Mowers, etc.): Honda Mower Engine, honda mower, hrx217hxa

Question
Hello, my HRX217HXA mower with a GCV190 engine would not start yesterday. The engine would make popping/backfire sounds thru the carb. Occassional white smoke from the muffler. I replaced the spark plug today and nothing changed, still won't start. The engine ran just fine last week. The mower is only 4 years old and has had yearly oil changes. Not sure what to do next.

Answer
Any chance it was left where rain could have got into the tank? Sounds like water in the tank to me. If there is even the remote chance water could have somehow, someway got into the tank, I would empty the tank, remove the carb bowl and dump that too, and do a fresh refuel....That white smoke is telling me there is water in the muffler. If it is in there It's very well  in the tank too.    Tom