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Gap Mower Spark Plug Video

By: Author John Cunningham. Published: 2020/10/14 at 9:49 am

This video walks you through the process of gapping your spark plug, including reading the spark plug, cleaning the spark plug, gapping the plug, and testing the spark. 

Gapping the plug is a simple job when you have the know-how, and it will make a huge difference in how your mower performs. If the plug gap is too small, the spark won’t be strong enough to ignite the fuel mix. If the gap is too big, the spark will occur too late, if at all, and put a heavy load on the armature (coil), possibly causing it to fail prematurely. This video will have you gapping like a pro in jig time.

Before working on your mower, be sure to remove the plug wire to prevent accidental starting; see “Repair Safety Video.”

You’ll find useful resources on this page, tips, and links to tools, parts, and supplies required to complete your repair.

Tools & Parts

To nail this procedure, you may need the following tools, parts, and supplies.


This is first on the list for good reason, WD solves a ton of problems. I won’t work without it, because I can’t. Picture links to

Ratchet Tool Set

Before we can do anything, we’ll need tools. I’ve selected this set as I own some Craftsman tools and while I have worn some out, they did do a ton of work. So, I expect this set will last the occasional user quite a long time. This set carries both metric and standard sockets, and that’s important because some mowers will have both types of fastener sizes. Includes spark plug sockets. Picture links to

Ignition Test Tool

This tool is used to check both the spark plug and the coil for spark. Sure you can check the spark without the tool, but it’s not as good; the tool is designed to stress the whole ignition system. Picture links to

Plug Gapper Tool

This tool isn’t strictly necessary if you have a feeler gauge, but it’s a lot easier to handle. If you haven’t guessed. You use this tool to check the gap of your spark plug, a simple effective tool. Picture links to

Wire Brush Set

Steel Brass and nylon wire brush set used to clean stubborn carbon from the spark plug electrode. The brush set is good quality, and various sizes will suit lots of mechanical uses, from cleaning plugs, electrical connectors, and carburetor parts to cleaning rust-covered fastener heads and threads. Picture links to

Carb Cleaner

When cleaning your carburetor, you’ll need this stuff. Gumming is a sticky substance that’s hard to shift. The carb cleaner will remove it; however, if your carb is really bad, save yourself some work, go ahead and buy a new carburetor. Picture links to

Feeler Gauge

The ABN 26-blade feeler gauge set is marked in SAE and metric. You’ll need this set to adjust the valve lash and it is useful when setting the armature/coil air gap. You can also use it to gap spark plugs. Picture links to