My mower will fire up fine, and run for about 10 to 15 minutes, then dies. It reminds me of an ignition coil problem with a vehicles. I have disassembled the top of the motor enclosure, and have found a magneto. The condition of the magneto is dirty, and partially rusty. Can I clean this with sandpaper? Does temperature effect a magneto as an ignition coil? If not, what is next to look at during the troubleshooting phase?
Yes, temperature definitely affects an ignition coil. According to the B&S website, the resistance inside the coil will go up as the temperature climbs. The resistance of a "room temperature" coil should be between 2,500 and 5,000 ohms. The measure this, contact the end of the spark plug wire with one probe and contact the laminated metal stack on the coil itself with the other probe. If the ohms are too high, then the coil is open. If the ohms are too low, then there is a short somewhere. Sanding the face of the laminate stack will not help any as rust doesn't usually affect the magnet. Also, magnets very rarely ever fail.
