The 500 Hour Inspection

Magnetos do require periodic maintenance. In 500 hours a four-cylinder magneto will generate over 150 million sparks at 2500 RPM. For an aircraft that flies 150 MPH that is the equivalent of 75,000 miles. That is impressive for an electromechanical device. Proper attention to detail on your magneto must be made every time the magneto is inspected.
During a 500 hour inspection, your magneto is disassembled to properly inspect all the components. Sintered bearings in the distributor block are baked with lubricant to re-infuse the bushings for maximum life. Capacitors are tested for leakage and proper capacitance. Contact points and cams are changed as required. Bearings are serviced and new seals installed. Impulse couplings are thoroughly inspected. If the magneto is pressurized it is checked on a flow bench to ensure the magneto will perform properly at high altitude. A post-inspection test run is made to verify that the coming in speed (lowest RPM the magneto produces a spark) and impulse coupling cut out speed (Highest RPM impulse coupling disconnects).