When your Craftsman lawn mower won't start, you might get very frustrated. Lawn mowers don't start for a variety of reasons, from no spark to no gas to no air. You need all three for a lawn mower engine to run smoothly. Troubleshooting your 6.75 HP Craftsman lawn mower yourself is well worth it--you could save hundreds of dollars that a mechanic might charge to do the same tests.
Open the gas tank, and make sure it is full. Press the primer button on the front of the engine three times to get fuel into the carburetor so the engine will be ready to start when you pull the cord.
Unscrew the air-filter cover on the left side of the engine. Examine the inside of the filter. If it is very dirty, the engine won't be getting enough air, and it won't start. install a new air filter; it is not expensive. Screw the air-filter cover back on.
Pull the spark-plug cap off the spark plug on the front of the engine. Unscrew the spark plug with the proper-size socket. Analyze the spark plug. There should be a small gap at the end of the plug (where the spark shocks across), and the base of the spark plug should be clean. If this base is oily, replace the spark plug. Screw the spark plug back in until it is snug, but not so tight that it will strip the engine-block threads. Place the spark-plug cap back on top of the spark plug.
Squeeze the choke bar to the base of the handlebars with one hand. Grab the pull-start rope with the other hand. Pull the rope quickly toward your shoulder repeatedly until the mower starts.