I recentley bought a Craftsman 4.0 HP mower at a yard sale, tested it before taking home and it fired right up. It did run a little rough so I replaced the air filter & spark-plug. Once again it fired right up and cut my lawn beutifully. The other day I went to mow the lawn and now it starts but dies after a couple of seconds. I've checked hose connections as well as the spark-plug connection. I'm stumped

You need to disassemble the carburetor and spray the with carb. cleaner. Make sure all small debris is out. Ckeck any gaskets for signs of ware. If they look bad, replace them; your carb. could be sucking air if so. Also check the fuel filter to see if gas is flowing through it.

Jim

It would be helpful to know which brand of engine you have, but here goes - if it is a tecumseh, remove the little brass "nut" that holds the float bowl on, it will have a hole by the hex part, a hole from the top going straight through, and a tiny, tiny hole at the top edge of the threads, clean these out with a small piece of wire brush - if briggs with independent carb, remove the "nut" and clean the two holes - if briggs with carb mounted to gas tank, remove the carb/tank assembly, remove carb, replace the diaphragm