What You Need to Know to Adjust a Spark Plug GapUpdated: Dec. 12, 2018
Be sure to set and adjust the spark plug gap for your particular engine!
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How to set spark plug gap
Photo 1: Check the gap with a gap gauge
Find the “gapping wire” that matches the recommended gap. Then slide it between the center and side electrodes. When the spark plug gap is correct, the gauge should drag slightly going in and out. If the spark plug gap is too large or the wire won’t fit, adjust the side electrode. You can also use a gap gauge like this one for this step.
Spark plugs don’t come gapped for your particular engine. For the best performance, you must gap the plug to the engine manufacturer’s specs. If you’re buying a plug for a small engine, ask the parts store to look up the gap size info for you. If the plugs are for your vehicle, find the info in the owner’s manual. Then adjust the spark plug gap as shown with a spark plug gapper.
Required Tools for this Spark Plug Gap Project
You’ll need a spark plug socket and a gap gauge.