Every time I go to start my mower it will run for 2 seconds and then stall out.?

Hello, I have a 1990 Ranchking by MTD ridding lawnmower. I just bought a new battery for it. And it has been sitting for about 4 years. I tried to get most of the old gas out of it. I cleaned the plug and air filter, and the oil is good. Every time I go to start it it will turn over and run for about 2 seconds, and then stall on me. Could someone please tell me what is wrong. Thanks.