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Flywheel Magnetos by American Bosch

American Bosch made many flywheel magnetos for small air cooled engines like the FY series all to familiar to the  Maytag restorers. The RF series was an early development found on Ideal air cooled engines, Caille outboards and others. More to follow on this group. They probably worked well back in the day and many survive in working condition. Coils often held up if kept dry. The manual for the RF describes testing the coil with a 6 volt battery with the coil in place if a coil tester is not handy. 


Condensers did not improve with age like wine. Always check for electrical leakage with an actual automotive condenser tester. The manual describes testing a condenser with a light bulb and a wall socket with AC. This is not a valid test as it does not test for leakage. The best way to test for leakage is with a DC source and a neon bulb if no condenser tester is available.  Lots of bad ones out there. Leave the used and new old stock devices for the curio collectors. These devices can soak up moisture and develop electrical leakage sitting on a shelf. If no electrical leakage is present they should come in at about 0.2MFD which is what most automotive condensers are. Automotive condensers are designed for this service and work well. There is a lot of real estate under the flywheel making this an easy fix.  For more service info on the American Bosch flywheel magnetos see the factory instruction and service manual section.