How to test a motorcycle coil. You can perform this test while the coil is on or off the bike. No key on is required. The only tools you will need is a voltmeter that can read ohms and a screwdriver. Most voltmeters do. First, make sure there is no spark and it’s not a fuel problem. Using the screwdriver, unplug the spark plug wire and place the screwdriver into it. With the key on, hold the screwdriver about a 1/8 of an inch away from any metal near the head or bike, as if to ground it out. Do not actually touch it, just hold it real close. While cranking the engine, check for a spark. If there is a spark, move to fuel, etc… because that means the coil is working. If there is no spark, now we would test the coil.
Check for a spark
Place your voltmeter to ohms. Testing a coil, I always remember 3 numbers, 3,5, and 10. This will make more sense by the end of this article.
Ohms setting on volt meter
One … Remove the wires from the coil. The wire connection to the left will be your power wire. The wire connection to the right will be your trigger connection. The wire to the spark plug (1,2,3, or 4) we will call your spark plug wire.
Remove wires from coil
Two … Use your volt meter to touch the power wire and the trigger wire. This test should read 3-5 ohms. If you are reading less than 3, or more than 5, replace your coil.
Volt meter leads on trigger and power wire
Three … Touch your voltmeter to the power and the spark plug wire. This test can be done touching any spark plug wire and the trigger if it is easier to reach. One lead must be on one trigger or power and the other side of the lead to any spark plug wire.
Volt meter leads on power and spark plug wire
Four … Notice the ohm reading while you are on the power side of the coil and the spark plug side. Your ohms should be at or around 10,000 ohms.
Check volt meter
If you are not at or around 10,000 ohms, replace your coil. I have made a video of this process and you can view it by clicking the link below.