This video walks you through the process of gapping your spark plug, including reading spark plug, cleaning spark plug, gapping the plug, and testing spark.
Gapping the plug is a simple job when you have the know-how, and it will make a huge difference to 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, 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 Amazon.com.
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 Amazon.com.
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 Amazon.com.
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 Amazon.com.
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, various sizes will suit lots of mechanical uses, from cleaning plugs, electrical connectors, carburetor parts, cleaning rust-covered fastener heads and threads. Picture links to Amazon.com.
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 Amazon.com.
The ABN 26 blade feeler gauge set is marked in SAE and metric. You’ll need this set to adjust valve lash and is useful when setting armature/coil air gap. You can also use it to gap spark plugs. Picture links to Amazon.com.
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John Cunningham is an Automotive Technician and writer at Lawnmowerfixed.com.
He’s been a mechanic for over twenty-five years and shares his know-how and hands-on experience in our DIY repair guides.
Johns’s fluff-free How-to guides help homeowners fix lawnmowers, tractor mowers, chainsaws, leaf blowers, power washers, generators, snow blowers, and more.