How to Test a Harley Coil


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How To Test A Harley Coil

Are you a Harley-Davidson biker who is looking to check the ignition coil of your Harley-Davidson bike, but don’t know how to? If so, then you are definitely in the right place.

Testing a Harley coil is a pretty simple process and involves turning off the ignition, disconnecting the spark plug from the coil, measuring the resistance between the coil connections with an ohmmeter, and measuring the resistance between the primary wire connections on the coil. When testing the Harley-Davidson coil, the resistance needs to be between 6,000 and 12,500 ohms. If the resistance is outside this range, it indicates a broken coil.

In this article, you will get to know all about the Harley-Davidson ignition coils, how to test a Harley coil, how does an ignition coil work, when do you need to replace the ignition coil, and more. Continue reading to get all the answers that you are looking for.

What is a Harley-Davidson ignition coil?

An ignition coil is a device attached to the spark plug of your Harley-Davidson bike. It’ll provide electricity to the plugin to contact the fuel mixture and help start your bike. If you are experiencing trouble starting your bike, there could be something wrong with the ignition coil. Most of the time, it’ll be smart to check all the items attached to your Harley-Davidson ignition coil.

When all the coils are working properly, they’ll provide the primary current for fuel combustion. These coils are connected to a battery, and they generate an electric spark to ignite the fuel mixture. If these coils aren’t working properly, it can lead to many different issues for your bike, including cold engine stalling or no-start issues.

If your Harley-Davidson bike isn’t running smoothly, then it might be because of a bad ignition coil. Harley-Davidson bikes have a specific engine setup that consists of a series of coils attached to the spark plugs. The ignition coils provide the spark needed for igniting the fuel mixture for your Harley-Davidson bike to start running.

How to test a Harley coil

By using an ohmmeter

The ignition coil on your Harley-Davidson bike serves to step up the low battery voltage to the high voltage needed for firing the spark plug. The coils are usually sealed water-tight components. As such, they aren’t necessarily repairable items. Routine checks on the coil are not necessary. They must be treated as a part of the troubleshooting procedure when the motorcycle becomes difficult to start or drives rough. Testing the coils tends to be a rather simple process and involves using an ohmmeter.

  1. Turn off your Harley-Davidson bike’s ignition.
  2. Disconnect the spark plug wires from the ignition coil with your hand. After that, disconnect the two smaller primary wires from the coil by making use of an open-ended wrench.
  3. After that, measure the resistance between the coil connections for the spark plugs using an ohmmeter. The resistance needs to be between 0.5 and 3 ohms. Any resistance value outside the range will indicate a broken coil.
  4. Lastly, measure the resistance between the two primary wire connections on the coil using an ohmmeter. The resistance needs to be between 6,000 to 12,500 ohms. Any resistance value outside that range will indicate a broken coil.
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By using a voltmeter

You can test your Harley-Davidson bike’s ignition coil by performing this simple test. To do that, follow these simple steps –

  1. Ensure that all of your Harley-Davidson bike’s electrical components are turned off
  2. Remove the spark plug for seeing whether any electricity is coming out of it or not. If you haven’t got a voltmeter with you, try to hook up an old Harley-Davidson part with a known working cell and then check for voltage.
  3. If there’s no electricity coming out of the spark plug, then you need to check for voltage at the coil. Unplug the connectors and test each wire individually until you find a good ground connection that has got continuity with a working part of your Harley-Davidson bike.

When do you need to replace the ignition coil?

If your Harley-Davidson bike is experiencing any of these issues, then it’ll be time to check out the ignition coils – 

  • The bike’s engine cranks but doesn’t start or runs poorly
  • Bike starts but shuts off immediately 
  • Idle speed problems
  • Hard starting at low RPMs

Check if there’s anything wrong with the ignition coils. If one or more of them looks burnt out, then it’ll be time for you to replace the Harley-Davidson bike’s ignition coil.

What are the bad coil symptoms of a Harley-Davidson ignition coil?

Engine backfiring

When a Harley-Davidson bike’s engine backfires, it’ll mean that the combustion process is occurring in the exterior of the engine’s combustion cylinders. The engine’s spark timing might be incorrect, which allows the air and unburnt fuel to go through the exhaust.

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Backfire can be heard if the engine is either excessively lean or rich. To compare, lean means that there’s less fuel in the engine than air, while rich implies more air than fuel.

Backfiring occurs when there’s unutilized fuel still present in the combustion cylinder after all the gases have left. After backfiring, the unutilized fuel or black smoke will pass through the combustion cylinder and into the exhaust pipe.

Bike stalling

The back wheel doesn’t have ample speed to match the engine’s RPM if the user releases the clutch too quickly. As a result, the engine will come to a halt. In most circumstances, this will happen due to a faulty or ineffective ignition coil.

The remaining coil will continue producing weak sparks until it doesn’t have enough strength to spark the spark plugs. If you’re driving continuously for a long period of time, the bike’s engine may stop or not start again once it has shut down.

Poor fuel efficiency

If your motorcycle consumes more fuel than it needs to, there are many warning indications. Your bike will have less mileage if that occurs. You need to check the ignition coil for any faults as it could be faulty.

Motorcycle engine fails to start

When your motorcycle’s engine doesn’t start, it is an indication of a dead coil. Single-coil engines are often prone to this signal, and the engine might make cranking noises, but there will be no sparks from the cylinders. This happens because of weak spark signals from the Harley-Davidson ignition coil.

Motorcycle engine misfiring

The motorcycle engine misfiring is an easy indication that your bike’s ignition coils are failing. The engine will produce a loud burr as it starts, indicating that it is sputtering or coughing. When the motorcycle moves at high speed, the engine would jerk and spit while, resulting in unpleasant vibes. The engine might even cease to start or idle once you reach the stop sign. 

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Rough idling

If the ignition coil is weak, or it fails, it’ll cause numerous symptoms, including rough idling, engine jerking, and power issues. When the engine is accelerating, you could notice a lack of interest and hesitation. As a result, your motorcycle will sound as if the power has been lost.

How to fix your Harley-Davidson bike’s bad coil

If your Harley-Davidson bike has a bad coil, there are three possible solutions that you can use to resolve the issue.

Replace the Harley coil

This is a simple and one of the most common ways to fix Harley-Davidson bike coils that have gone bad. You can replace the Harley coil with one that works properly. You can purchase it from any Harley-Davidson dealership or online retailers like Amazon and eBay.

Repair the coil

Another potential option for your bike would be to repair the ignition coil on your own. This might be more challenging, as Harley-Davidson ignition coils are pretty complex and have many components.

Replace the coil with a CDI unit

Replacing the ignition with a CDI unit will require you to remove all of your bike’s current electrical wiring. This can be difficult for beginner mechanics or newbie owners. In addition, Harley-Davidson bikes with a CDI unit don’t have any current coils. Instead, they use one or more coil packs that are external to the motorcycle.

Harley-Davidson Motorcycle Coil


How much does it cost to replace a Harley-Davidson ignition coil?

Replacing a Harley-Davidson ignition coil ranges from $50 to $90 depending on where you’re buying it from. It is recommended that you should replace the coils every 15,000 miles.

Where does the Harley-Davidson ignition coil get its power?

An ignition will get its power from the Harley-Davidson battery. The battery will send the current from one terminal to the other, creating an electric spark that feeds through the bike’s primary winding and into the secondary winding.

Can a bad Harley ignition coil result in transmission problems?

A bad Harley coil could result in many transmission problems. The bike could have trouble shifting gears, the engine might not run efficiently, and the idle might also become irregular.

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