At the start of the spring season, nothing can be more frustrating than a mower that won't start. But the solution could be as easy as checking the spark plug for damage. Your operator's manual offers instructions on removing the plug. Once removed, check the plug's porcelain area for cracks. If it's damaged, throw it away. You should never use a cracked plug. If the electrode end is oily and dirty, you can use a wire brush to clean it. Be sure to set the gap for the proper distance. Again, the operator's manual can give you all the information you need. Or, for peace of mind, just replace the plug every spring.