Walk Behind Lawn Mowers

James,

White smoke indicates that you have moisture in your gas. Drain the gas tank by disconnecting the fuel line into an appropriate container, also drain the carburetor fuel bowl, and clean it out good, its also a good time while you have the fuel bowl off to spray a little carburetor cleaner inside the carburetor to clean it out and to dry any moisture or water left inside the carburetor. If you have a primer bulb also remember to push that a few times too, and get any liquid out of it. Moisture and Water will collect in gasoline in just a few months of sitting, and then it gets trapped inside the carburetor and water will not burn, so the engine will not start. After its all cleaned out, buy some fresh gasoline, reconnect everything, put the fresh gasoline in, prime the engine, or If there is No primer it may take a few extra pulls like 5 or 6 to initially get the gas back into the carburetor, and it should then start. Also a mistake that some people make is they buy a large gas can like 2, 3, or 5 gallon can, then fill it up at the beginning of the season and then let it sit all season until they use it up.  They would be better getting a 1 gallon or smaller can and just get fresh gas a little more often, also fuel stabilizers really do help. So when you get a full can of fresh fuel don't forget to add the recommended fuel stabilizer to the gas, that will definitely help. I hope this Info helps you.