Understanding the Ins and Outs of Spark Plugs

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High-quality spark plugs provide more power and more reliable engine performance while also increasing the efficiency of the engine. A good spark plug is designed to effectively ignite fuel and burn it quickly. The ultimate goal is to find spark plugs that are in the correct heat range for your engine so that the fuel-air mixture is not prone to pre-ignition from too much heat, nor to incomplete burning and fouled plugs caused by being too cold.


Spark plugs provide a connection from the electrical distribution system of your machine to the engine. They are timed so that each plug receives a specific electrical current in its turn. As the current races through the outer conductor, it will create an arc to the center post. This arc puts off the heat that is required to ignite the fuel/air mixture. Spark plugs vary in size, but they also come in a variety of different conductor types and insulator options, and the conductors themselves can be shortened or elongated to produce a hotter or cooler operating range.


The center electrode of the spark plug includes the tip and is run through a ceramic or other insulating material that prevents current from escaping or bleeding out of the plug. This electrode can be made of or plated with nickel, platinum, iridium or other precious metals to increase the conductivity of the plug. Inspecting the tip for signs of buildup from unburnt fuel should be done at regular intervals.

The ground electrode is the angled pin that sticks out past the tip of the center electrode. The gap between the two is what causes the arc to happen. The gap can be adjusted by gently moving the pin closer or further from the tip to change the length of the arc. This should be done with the help of proper measuring tools and according to the manufacturer’s directions for recommended gap.

Performance Ratings

The performance of any given spark plug will be based on the materials that are used in its construction and the intended heat range of the device. Spark plugs are rated and stamped to designate their optimal heat range as well as any special plating or other improvements made to the conducting surfaces.


If your engine is running rough or misfiring on a regular basis, or if fuel consumption has gotten worse over time, it may be time to inspect your spark plugs. Spark plugs that are running too hot will be visibly discolored and indicate that the fuel is being burned before reaching the proper fuel-air mixture in the cylinder, causing early ignition and uneven operation. On the other hand, if the spark plugs have an oily residue left behind or if the gap is completely bridged by thick grime, it is a sign that the spark plug was not getting hot enough to completely burn the fuel away. As the residue is built up, the plug continues to lose its ability to ignite any additional fuel. Any obvious damage to the tip or the ground electrode should also be addressed by replacing the plugs.

Where to find replacement spark plugs

CubParts.com carries a huge selection of performance spark plugs specifically for your outdoor equipment. They can help you find the plugs that are designed for your small engine and Cub Cadet machinery with their comprehensive parts finder tool. 

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