How to Change Spark Plugs on a Cub Cadet

Close-up of grass Periodically replacing the spark plug with help ensure that the engine operates at its greatest efficiency. Image Credit: Jupiterimages/Comstock/Getty Images

Cub Cadet lawn tractors are equipped with internal combustion engines that run on gasoline. As with other gasoline engines, the Cub Cadet's engine uses a spark plug to ignite the fuel. Over time, spark plugs tend to corrode, and their effectiveness diminishes. It is for this reason that Cub Cadet recommends changing the plug every 200 hours of operation.

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Removing the Spark Plug

The engine's spark plug is under the hood and against the right side of the engine. Note that a spark plug wire is attached to the tip of the plug. You must detach the wire from the plug before you can remove the plug. Grasp the wire firmly at the rubber boot at the base of the wire, where the wire attaches to the plug, and pull the wire off the plug. Remove a stubborn wire by twisting the boot before pulling it off the plug. If dirt and debris surround the base of the spark plug, it is important to remove the debris before removing the plug to prevent the contaminants from falling into the engine. Turn the spark plug in a counterclockwise direction with a 5/8-inch deep-socket attached to a socket wrench until the plug detaches from the engine.

Gapping the New Plug

A common mistake when replacing spark plugs is to install the new plugs right out of the box. Spark plugs must be checked and, if necessary, adjusted. This adjustment process is often referred to as "gapping" a plug. The gap refers to the distance between the metal electrodes at the tip of the engine-side of the plug. The proper gap for the Cub Cadet engine is 0.030 inch and is measured with a tool called a feeler gauge. Feeler gauges have either a number of wires or flexible metal blades of different widths. Insert the wire or blade of the feeler gauge between the spark plug's two electrodes. The gauge should fit snugly between the electrodes. Adjust this distance to 0.030 inch, if necessary, by bending the hooked-tip of the plug in the appropriate direction.

Installing the New Plug

Installing the new plug is a bit more involved than simply tightening it into the engine. If the plug is tightened too much, there is a risk the plug can break. If not tightened enough, compressed air from the engine might pass over the plug's threads and the engine may not start. It is for this reason that you should use a torque wrench to tighten the plug. A torque wrench measures the amount of force applied to the wrench. A number of torque wrench designs exist, so consult the wrench's instruction manual if in doubt on how to use the wrench. Tighten the spark plug into the engine to between 28 and 32 ft. lb. of torque with the torque wrench.

Replacing the spark plug is an important part of regular maintenance, but other components also require periodic attention. The louvers within the tractor's hood are designed to vent the hot air produced by the engine to keep the engine cool. Over time, debris can accumulate in these louvers and prevent venting. In extreme cases the engine can overheat and require substantial repairs. It is for this reason that you should clean the louvers after every 10 hours of operation. The engine is equipped with an oil filter and an air filter. Replace both components and change the engine's oil after every 100 hours of operation or once a year, whichever occurs first. It is also important to clean the two battery terminals after every 10 hours of operation, as corrosion can accumulate on the terminals and cause an electrical supply problem.