Field & Stream Online Editors
Field & Stream Online Editors

Hey, buddy: got plugs? fresh spark plugs, that is. Around my way, changing plugs is as much a rite of spring as digging out the fishing tackle or greasing the boat trailer. From ATVs and chain saws to outboard motors and lawn mowers, all the gas-powered gear that sat over a long winter now needs attention.

After years of trial, error, and rough-running frustration, I’ve finally made a routine of simply putting fresh spark plugs in everything at the start of the season. They’re cheap, easy to install, and go a long way in making everything start and run smoothly on the first try. Simple as the process is, plug changing does have some pitfalls. Here are some tips to keep you out of trouble.

Use a Boot-Puller
Never yank or pull on an ignition wire to remove the protective boot off the top of a spark plug. Doing so is a tempting shortcut, but it’ll most often snap the ignition wire at the clip-on plug connection. Worse, you won’t be able to see the break, because the connection-broken or not-is covered by the boot. Pick up an inexpensive boot-puller at your local auto-parts store. This looks like an elongated pair of pliers, the gripping ends of which are formed in the shape of a spark-plug boot. The tool makes removing a boot easy, and it won’t damage the connection.

Check the Gap
Check the spark-plug gap (the distance between the center electrode and L-shaped ground electrode at the end of the plug) before installing a new plug. The specification should appear in your engine or equipment manual. The gap is most often factory-set by the plug maker, but checking and adjusting it is easy.

You’ll need an inexpensive gapping tool; most commonly, a small metal disk, the edge of which tapers in thickness and is imprinted for gap setting. Slide the tool’s edge into the plug gap and rotate the disk until it’s barely tight between the electrodes. Read the corresponding gap dimension. If it’s too small, gently bend the ground electrode slightly outward. If it’s too much, bend the electrode inward.

Finally, you’ll need a deep socket wrench (or special spark-plug socket with a rubber insert that retains the plug as you position it) for installing the new plug. Turn the new plug gently by hand into the cylinder head, making sure it turns easily and smoothly until seated on the cylinder-head face. Be careful here: Cross-threading and forcing the plug will mean an expensive repair job. Then give the plug a final tightening with your socket wrench as per the engine maker’s specs.