* Low battery. If the battery is low, it won't have enough power to turn the starter motor. Check the battery voltage with a multimeter and make sure it's at least 12 volts. If the battery is low, charge it or replace it.
* Bad starter solenoid. The starter solenoid is responsible for engaging the starter motor with the flywheel. If the solenoid is bad, it won't be able to complete the circuit and the starter motor won't turn. Test the solenoid by jumping the terminals with a screwdriver. If the starter motor turns, the solenoid is bad and needs to be replaced.
* Bad starter motor. If the starter motor is bad, it won't be able to turn the flywheel. Test the starter motor by applying power directly to the terminals. If the starter motor doesn't turn, it's bad and needs to be replaced.
* Bad ignition switch. The ignition switch is responsible for completing the circuit between the battery and the starter solenoid. If the ignition switch is bad, it won't be able to complete the circuit and the starter motor won't turn. Test the ignition switch by turning the key to the "Start" position and checking for power at the starter solenoid. If there's no power, the ignition switch is bad and needs to be replaced.
If you've checked all of these things and the starter motor still doesn't turn, you may have a more serious problem with the engine. You should take your Cub Cadet to a qualified repair shop for further diagnosis and repair.
