The best way to test a riding lawn mower starter is to use an ohm meter. This device determines the continuity of electrical currents in circuits attached to motors, cables and fuses. An infinity or OL reading means the starter circuit is bad.
If a starter switch on a riding lawn mower ignites the motor only intermittently, this indicates that it needs to be replaced. Likewise, replace a starter that is difficult to turn on. Another issue that may be causing starter malfunction is a defective spark plug. To fix this problem, remove the spark plug, clean the plug contact, and install a new spark plug.