Knowing about a bad ignition coil on a Yamaha V-Star 650 motorcycle may prevent you from getting stuck away from home. If you are experiencing start-up problems, consider testing the bike's ignition coil. Inside the device's casing, two coils of wire increase the voltage from the battery so that the motorcycle's engine starts. Both coils need to be able to limit the flow of electricity through them to work properly. In other words, their resistance must be a specific value.
Turn on the digital multimeter then change the measurement dial to the lowest range resistance setting. Resistance is measured in ohms which is designated by the capital Greek letter omega. The lowest setting is designated by a "200," meaning the multimeter will measure in the 0 to 200 ohm range.
Unplug the wire that connects the ignition coil to the spark plugs. Disconnect the ignition coil from the black wiring harness of the motorcycle. There will be two terminals on the ignition coil. One is either red or black and the other is orange or grey.
Connect the red (positive) lead of the multimeter to the red (black) terminal of the ignition coil. Connect the black (positive) lead of the multimeter to the orange (grey) terminal of the ignition coil. The reading on the screen of the multimeter is for the primary coil and should be between 3.8 and 4.6 ohms. If the resistance does not fall in this range, replace the whole ignition coil. Disconnect the multimeter cables from the ignition coil.
Connect the red cable of the multimeter to the spark plug lead of the ignition coil. Connect the black multimeter cable to the red (black) terminal of the ignition coil. This set-up is for secondary coil measurement.
Switch the measurement dial on the multimeter to the "20k" ohm setting which stands for 20 kilo-ohms or 20 thousand ohms. The multimeter now reads resistances in the 0 to 20,000 ohm range. The secondary coil resistance should be in the range of 10.1 and 15.1 kilo-ohms or it is faulty.
The bike's ignition coil uses electromagnetic induction to increase the battery voltage to a level needed to fire the spark plugs and start fuel combustion in the engine.