In this video, we’ll remove, clean, and refit the spark plug. A dirty plug will cause a ton of issues, including no start; surging; rough running; hot start problems; no power.
It’s a common issue, oil, carbon, over-fueling, or stale gas will cause the plug to foul. Continuous fouling however is a sign of a problem. Typical causes of continuous fouling include Bad plug; Wrong plug; Too much engine oil; Bad gas; Bad armature (coil); Engine wear; Valve lash out of spec; Faulty carburetor.
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.
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 lot 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. Set includes spark plug sockets. Picture links to Amazon.com.
Every home needs a Dvom (Digital Volt Ohm Meter). It’s used to check for continuity in lawn mower wiring, and for voltage when there’s a battery fitted. But don’t use this tool to check spark, that will kill it. I use mine every day. I have the previous model to this and it’s still doing its job. Picture links to Amazon.com.
Now, this tool is a must-have if you’re removing the flywheel. Why would you want to remove the flywheel? Sometimes the flywheel key shears. The key is an inexpensive fail-safe component that prevents crankshaft damage. It’s easy to fix when you’ve got this tool. Picture links to Amazon.com.
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
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.
I love DeWalt, they make quality tools. This heavy-duty but lightweight 1/2 inch impact wrench makes short work of stubborn bolts like flywheel nuts and rusty blade fasteners. Up to 700 ft. lbs. of torque on tap, I keep one in the trunk of our family car, which makes a flat almost enjoyable. Picture links to Amazon.com.
I use a Dewalt screw gun (also a drill) in the workshop to speed up the process of removing engine covers, carburetor bolts, Armature bolts, etc. It’s a brushless motor and as tough as nails, I drove over it a few times – still works great! Batteries are interchangeable and so if you have a Dewalt product already you won’t need the battery. Picture links to Amazon.com.
Teng 1/2 Torque wrench, a fantastic tool I use it every day, and mine is still going strong. A torque wrench is advised for tightening components such as flywheel nuts and blades. The torque spec of these components is very important. Picture links to Amazon.com. If you are buying a torque wrench, check out my review of Teng torque wrench, it’s the wrench I use.
Piston Stop Tool
Universal piston stop tool 10mm and 14mm, used to lock the crankshaft when removing and tightening the flywheel nut. Picture links to Amazon.com.
Blade Holding Tool
The very useful blade holding tool is used to hold the blade steady while the blade bolt is loosened and tightened. Picture links to Amazon.com.
Wire Brush Kit
Stainless for heavy-duty and brass for and brass wire brush kit for heavy-duty and finer applications like electrical connections and softer metals. Picture links to Amazon.com.
- About the Author
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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.