Why wont it start ? totally dead - Troy Bilt 5.5hp Self Propelled Mower

Check the following, Fuel, Spark, and Compression. To test fuel take the air filter off and spray starter fluid in it and try and start it. if it starts a little then it's a fuel problem (carb or bad gas). Test spark, remove the spark plug, put the coil line back on the plug and ground the spark plug to something metal. Try to start it and see if there is a spark (helps to have a friend to do this). Compression, If you don't have a compression gauge then a crude way is to have a friend put his finger over the spark plug hole while you try and start it (he should feel pressure) (if not then it may be the head gasket, valves are not seated or the piston rings) If pressure is felt then the only thing is the key way on the fly wheel is shredded.