I Have to Keep Changing the Spark Plug in My Push Mower

Wrong Plug

• Look in your owner's manual to make sure you're using the right kind of spark plug. Even under normal operating conditions, a plug unsuited to the demands of your particular mower is likely to have a shorter life span, resulting in frequent replacement. If you can't find the operator's manual that came with the mower, look online or call the manufacturer to get their recommendation on which spark plug to use.

Fuel/Air Mixture

• A critical part of the internal combustion process occurs in the carburetor, where the air and gas are mixed. If the ratio is off, resulting in too lean or too rich of a mixture, expect that the imbalance will manifest itself in the spark plug in the form of carbon buildup. A visual inspection of the plug can reveal a gas/air mix issue. If you see gunk or black sooty film over the end of the plug, there's a good chance you need to have the carburetor adjusted.

Engine Timing

• For a push mower engine to operate properly, the ignition timing must be precisely set to spark the plug in conjunction with the down stroke of the piston. When the timing is off, the plug fires too early or too late and can experience premature wear and tear. If you suspect this is the problem, clean and set the points if you have an older machine. Newer lawnmowers have an electronic ignition module which can be replaced.

Considerations

• Under normal conditions, a single spark plug should easily last through an entire mowing season, and some are good for years of use, though it isn't a bad idea to install a new plug before the first mowing of the summer. Though defective plugs do appear from time to time, it's more common to find a spark plug fouled due to another problem within the lawnmower's fuel or ignition system. If you don't have the expertise to troubleshoot the issue on your own, call your local small engine repair specialist.