VIDEO: How to Change a Harley Davidson’s Spark Plugs

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Regular maintenance on your Harley Davidson is important and
changing the spark plugs is something that’s easy to do. Spark
plugs should be changed every five to ten thousand miles. If you have
performance problems during that time, the spark plugs should be
checker. It will help your bike to run better and can save a trip into
the shop. When doing spark plug replacements on a Harley Davidson, it’s
highly recommended to use only the stock spark plugs from Harley
Davidson. Many vehicles work just as well with different brands, but
it’s not so with Harleys.

Tools Needed

  • Rachet and Spark Plug Socket
  • Plug Gap Guage
  • Gapping Tool


  1. Remove your Spark Plugs.
    There will be two plugs – one
    located in the front part of the engine and one on the rear
    portion. Remove the spark plug boots and then take out the spark
    plugs. You can use a standard ratchet, but you’ll want to get a plug
    socket. It’s a special socket designed to grip and turn the spark plug
    without damaging it.

  2. Inspect the Spark
    Look over the spark plugs after you
    remove them. Be careful to check for coloration. What you want to
    see is a tan/brown color around the ceramic. Black indicates a
    mixture that is too rich – meaning too much fuel to air. White
    shows that the motorcycle’s mix is too lean.

  3. Set
    the Plug Gap
    Get your new plugs and check the plug gap
    on them. There are tools specifically designed for this purpose.
    The right plug gap should be in the range of 38 to 42 thousandths
    of an inch.  Adjust the gap with a gapping tool if necessary.

  4. Install the New Plugs
    You just reverse the process
    you used
    to take out the old spark plugs to install the new ones. Use the
    plug socket and ratchet to put your new plugs in. Inspect the plug
    boot and wire for any breaks or residue. If it’s dirty you should
    clean it. If there are cracks you will want to replace the wire.
    Just as you should use stock Harley Davidson plugs, if you need to
    replace the wires be sure to use stock wires. If the wires check out
    fine, just place them back onto the spark plugs. They should snap into
    place with an audible click.

Spark plug replacements are among the easiest maintenance you can do
on any vehicle. With your Harley Davidson motorcycle they can be very
important. Doing it yourself can save you some money and a trip to the

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