Spark Plug Installation Videos
Spark Plug How-To-Video
Replacing spark plugs can be a simple job, if you take things one step at a time.
Replacing spark plugs can be a simple job, if you take things one step at a time. Given a basic understanding of mechanical matters, here's a guide to the proper procedures in changing spark plugs.
- Carefully remove the spark plug wires. Grasp the plug wire boot, twist about one-quarter turn to break the seal, then lift straight off. Use plug boot pullers if the boot doesn't break free easily. Number plug wires with tape as you remove the to avoid crossing them. (illus. 1)
- Loosen each spark plug so it can be removed. Clean the seat area with a blast of compressed air, or by blowing through a soda straw. This prevents dirt from falling into the combustion chamber when the old plugs are removed. (illus. 2)
- Remove the plugs and line them up in cylinder order. Inspection of the firing ends of the plugs can identify a number of engine problems that may need correction. (illus. 3)
- Gap new plugs as recommended in your owner's manual or a Spark Plug Catalog. Use a feeler gauge to measure the gap between the center and ground electrode. The gauge should pass through snugly but easily. If it's too loose or too tight, reset the gap.
- Screw new plugs in by hand until tight. If the plug starts to go in hard, use a thread chaser to clean the threads. Use a torque wrench to tighten the spark plugs following the manufacturer's recommendations, or refer to a torque chart in the Spark Plug Catalog. If you don't have a torque wrench, see the bottom of the torque chart for hand tightening recommendations.
- Replace spark plug wires in the correct order. Check to see if the boots are brittle or cracked, and if there is corrosion on the connector inside the boot. If any of these conditions are present, the spark plug wire should be replaced.
- Start the engine. If it misfires or idles roughly, the wires are crossed or not connected to the plugs correctly. Check the firing order and connections closely.
Autolite Motorcyclist changes plugs on a BMW & Harley