Small Engine Troubleshooting Problems? Ask a Mechanic Now.
Do you hear any noise/ click when you turn the key on? Fuel solenoid in carburetor should click when key is turned on. If no click, there is no voltage to the key switch. Do you have a voltmeter to see if there is voltage at the key switch? It has to have full battery voltage.
Seat switch, brake switch, either will keep starter from engaging, Is seat switch and harness ok?
When did mower last run?