The ignition coil on any motorcycle, including the Sportster 1200, is used to boost the battery voltage to fire the spark plug. An ignition coil is a water-tight component, which is sealed and not suitable for making internal repairs. So if it breaks you’ll need to replace the entire part. This means that the ignition coil should be checked whenever you are troubleshooting a starting or ignition problem with the bike. To do this you need to use a tool that can detect electrical current.
1. Turn the key in the ignition to the “Off’ position. Take the key out of the ignition.
2. Pull the spark plug wires off of the spark plugs and then disconnect them from the ignition coil
3. Disconnect the smaller primary wires from the ignition coil with the wrench.
4. Connect the red colored robe for the ohmmeter on the “Primary” wire lead on the ignition coil. This is the wire that is connected to the Points or the CDI. Connect the black colored probe to a metal ground, such as the frame.
5. Read the display on the ohmmeter. The normal reading should be between .5 to 1.5 ohms. If the reading is above this range the ignition coil needs to be replaced.
6. Connect the red colored probe to the secondary wire on the ignition coil. This is the wire that is running to the spark plug caps.
7. Read the display on the ohmmeter. The normal reading should be between 6,000 and 13,000 ohms. If the reading is below this range the ignition coil needs to be replaced.