HD Spark Plugs Service

Premium Video Preview: Log in or become a member to get full access.
Duration: 7:41

Membership Options

Premium

Sign up for premium membership and get access to our best Harley repair videos and step-by-step instructional projects. Learn new techniques and tips from friendly experts. Anytime. Anywhere.
Monthly $8.00
Annually $59.00

Gold

Upgrade to GOLD membership and get unlimited access to our entire library of premium Harley repair videos, receive discounts on DVDs, video downloads, and classes in the shop. In addition, you’ll receive sixteen video downloads, access to GOLD member LIVE events, and so much more!
Annually $110.00

In this video, Bob walks us through spark plug replacement. It is a fairly quick and easy service point but it is not a task that should be taken lightly. Cross threading a spark plug into a cylinder head, or dropping debris into your cylinder will turn a 5 minute service point into an expensive, time consuming repair.

You Have To Be Clean

Start by carefully removing the plug wires from the HD spark plugs. It is best to lift from the bottom of the spark plug boot. If you notice a lot of road debris around the base of the HD spark plugs; grab safety glasses and blow out this area with compressed air. Never risk removing your spark plugs if there is a chance of outside contamination or debris falling into your motor.

Remove and Read

Use the correct spark plug socket to remove your plugs. Your H.D. service manual has a chart that you can reference when inspecting the plugs that are being removed. Reading your plugs can help to determine how your engine is running/performing.

The Right Gap

Always use the best quality HD spark plugs that you can afford. It is, also, very important to properly gap your new plugs. Never take for granted that your new plugs are correctly gapped by the manufacturer. These plugs need to be gapped between .038 and .043. Apply never seize to the threads of the new plugs. This keeps the plug from seizing in the head and also aids in installation. Always start threading in the spark plugs by hand. Snug them, and torque to factory spec.

Use dielectric grease at both ends of the spark plug wires. This helps to keep out moisture and, also, aids in wire installation. Remove one wire at a time from your ignition coil. This is a single fire ignition. If the wires are swapped, the m/c will not run. Trying to start, or run the m/c with the wires reversed can be damaging.

Changing HD spark plugs is to be performed at every major service. Follow Bob’s instructions & advice. Service this area of your motorcycle thoroughly, perfectly, every time.

Up Next: Twin Cam 103 Harley Air Shocks