How can I start my craftsman push mower?

I have a 6.75 horse B&S engine on a craftsman push mower. When I took the blade off to get it sharpened some of the gas came through the front of the engine. Since then it would start, but only ran for a couple seconds and would then die. Also white smoke would spew from the exhaust. I have poured dry gas in it. Emptied the tank and replaced with all new gas. Replaced the spark plug. Took apart the front portion of the engine in hopes that it would dry out. Nothing has worked. It will not even start now. ANy other suggestions to try?