Small Engines (Lawn Mowers, etc.): mower wont restart, back fire, push mower

Question
I hope you can help me.I got a little used push mower and it has worked fine the past two weekends.I was mowing along and I ran out of gas,its happens offten because it has a very small gas tank.I went in the house got a drink etc,went back out about 20 mins latter refilled the gas it started and ran for about 30 sec's and seemed to be lacking power.I have not been able to start it since then.Right after it stalled I was trying to start it and it made what sounded like a baby back fire.
Thanks
Luke

Answer
 Hello Luke:

 There are 2 possible causes for your Problem. 1- Clean and Overhaul the Carb.  2- The valves need to be ReGround and valve lash set. Try the Carb First. It sounds like trash got into the Carb.  Hope this Helps.

 Good Luck

 Respectfully

 John