Troubleshoot a Motorcycle Ignition Coil
The ignition coil on a motorcycle is an electrical component within the ignition system. It receives a low voltage from the bike and steps it up to a very high voltage. This voltage is then sent via heavy-duty spark plug wires to fire the plugs. The coil contains primary and secondary windings wrapped around an iron core. It is sealed and cannot be repaired. When an ignition coil ceases to function properly, it must be replaced. Fortunately, a coil’s function is easily tested with a standard ohmmeter.
1. Shut off the motorcycle. Allow the bike to cool down to the touch.
2. Pull the spark plug wires off of the coil. Unscrew the remaining two wires attached to the coil with an appropriate-sized wrench.
3. Set the ohmmeter to measure Rx1 ohms. Connect the meter’s probes to the coil’s two smaller connectors. The ohmmeter should indicate 2.5 to 3.1 ohms. Any other reading indicates a bad coil.
4. Set the ohmmeter to measure Rx1,000 ohms. Connect the meter’s probes to the coil’s two larger, spark plug wire connections. The meter should now indicate 10,000 to 12,500 ohms. Readings outside of this range indicate a bad coil.