Cleaning Spark Plug video

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. 

Over View

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

A dirty spark plug will cause a ton of problems. It’s a common issue oil, carbon, over fueling issue, or stale gas will cause the plug to foul.

Continuous fouling however is a sign of a problem. Typical causes of continues 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”.

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 type of fastener sizes. Set includes spark plug sockets. Picture links to Amazon.com


DVOM

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 everyday. I have the previous model to this and it's still doing its job. Picture links to Amazon.com

Flywheel Puller

Now this tool is a must have if you're removing the flywheel. Why would want to remove the flywheel? Sometimes the flywheel key shears, it stops your engine starting. The key is really cheap and it's easy to fix when you've got this tool. Picture links to Amazon.com

Ignition Tester

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

Feeler gauge

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

Impact Wrench

I love DeWalt, they're 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. Upto 700 ft lbs of torque on tap, I keep one in the trunk of our family car, makes a flat almost enjoyable. Picture links to Amazon.com

Drill/Screw Gun

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 driven 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

Torque Wrench

Teng 1/2 Torque wrench, 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 considering buying a torque wrench, definitely check out my review of Teng torque wrench.


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

Very useful blade holding tool, 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

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Auto Technician and Writer at Lawnmowerfixed | Website

John Cunningham is an Automotive Technician and writer on Lawnmowerfixed.com. I've been a mechanic for over twenty years, I use my knowledge and experience to write "How to" articles that help fellow gear-heads with all aspects of mechanical repairs, from lawn mowers to classic cars.