check the carberator, it may need to be replaced. It could have varnish that is clogged in it. It is a simple fix just buy a new one if that is the problem. It was with ours.

Your lawnmower's engine (like any engine) needs three thing to run, air, fuel and a spark.Check the air filter to be sure it's not clogged. You can even remove it just to start it, if it runs replace it with a new one before mowing. Also check to see if the 'choke' is on. The choke plate restricts air to richen the air/fuel mix but may be preventing it from starting. It can be checked with the air filter assembly removed by shining a flashlight down the carb and moving the choke lever. Next make sure you have gas and the gas is getting to the carb. trace the fuel line from the tank to the carb to be sure there is no shutoff valve. If there is make sure it is in the open position. Lastly check for a spark. Remove the spark plug wire and with a set of plastic salad tongs (or something similar) hold the wire tip about a quarter of an inch away from the metal fins of the engine and have someone crank the engine. You should see and hear the 'tick' of a spark. If you get a spark here remove the spark plug and clip the wire back on. Hold (again with tongs) the spark plug against the metal engine. You should see the spark jump the gap of the plug. The gap (space between electrodes)should be roughly the thickness of a matchbook cover. If you never got a spark in the first place there is a kill switch wire or it may have a keyswitch wire. Both can be bypassed to troublshoot but it is unsafe to leave it bypassed. Follow the kill wire to the point where it attatches to metal. It will be a connector or it may be screwed on. To bypass remove that wire from the metal and isulate it with tape. If the engine starts replace the kill (or ''Stop'') switch. To bypass the key switch remove one of the two wires on it and attempt to start it. If that doesn't work hold the two wires togeather and try again. If one or the other works replace the key switch. Good luck yo...

I don't think its the plugs if it's turning over........I'd check the gas.