my yard machine 20hp 46in cut will not start.......motor turns over but seems like its not getting fire

Hi,
The keyswitch is a common failure point and to taken out of the circuit you would look for the white wire that either has a round plug joining it or connected to a spade terminal that fastens to a threaded post. Should be on the right side or front of the engine. This takes the ignition ground out of the circuit. Another consideration is do you hear the fuel shutoff solenoid click when turning to the on position, if so equiped. Both of these point to that switch. Note: the engine will not shut off by the switch except by the fuel solenoid, if present.
Peace,
Clarke