While there are other routine maintenance tasks involved in owning a lawnmower, the annual tune-up routine consists of just three tasks:
Changing the oilChanging the spark plugChanging/cleaning the air filter
Before performing a tuneup, it’s best if the engine is just slightly warm. Put just enough gas in the gas tank to get the mower running, then start the engine and let it run out of gas. As a final safety precaution, disconnect the spark plug wire so that the engine can’t start accidentally.
Tools and Supplies You Will Need
Motor oil Old toothbrush Wrenches Rags Motor oil Oil pan New spark plug Spark plug gapper tool Screwdriver Grease-cutting soap Paper towels
Instructions
Most mowers will operate smoothly for many years with just these three annual tuneup actions. More serious repairs need to be considered only if this tuneup fails to keep your mower running.
How to Change Oil
How to Change the Spark Plug
How to Change (or Clean) the Air Filter
Before changing/cleaning the air filter, first determine whether your machine has a paper or foam air filter. Paper air filters are replaced, while the foam ones are cleaned. On the underside of the mower, locate the oil plug. This is usually located on the bottom side of the mower deck, and it may be covered with grass residue if you don’t clean the bottom of your mower routinely. Prop up your mower right-side-up on blocks, at a slight tilt toward the drain plug. Place an oil pan or other shallow container below the plug, then unscrew the plug counterclockwise and allow all the oil in the crankcase to drain out. You will likely notice how dirty and cloudy this oil is—not like the translucent amber color of new oil. Lift the mower off the blocks, set it on a level surface, then fill the crankcase with new oil to the correct level. Replace the cap and dipstick. Refill the gas tank then reconnect the spark plug wire. Start the mower and make sure there are no oil leaks. Clean the housing around the spark plug with an old toothbrush and rags. It is important that the area around the spark plug is clean so that debris can’t get inside the engine cylinder when you remove the plug. Remove the old spark plug with a socket wrench and deep socket (there are special deep sockets designed for removing spark plugs).
How to Replace a Paper Filter
How to Clean a Foam Air Filter
Disconnect the spark plug wire to eliminate any chance of accidental starting. Unscrew the air filter cover. The cover is usually held in place by a long screw that runs through the filter and is threaded into the bottom of the air filter housing, or it can be secured with a wing nut threaded onto a bolt running through the air filter housing. Removing the screw or nut frees the cover of the air filter, allowing it to be removed. Remove the old air filter and insert a matching new filter, so the pleats face outward. Reposition the air filter cover, and secure it with the screw or wing nut. Reconnect the spark plug, then start the mower to test its operation. Disconnect the spark plug wire to eliminate any chance of accidental starting. Unscrew the air filter cover and remove it. The cover is usually held in place by a long screw, or with a wing nut that is threaded onto a bolt running all the way through the air filter housing. Lift out the foam filter. Wash the foam filter with hot water and a grease-cutting liquid soap. Rinse the filter thoroughly, then press it with paper towels to remove as much water as possible. (Alternately, some users like to rinse the foam in kerosine, but if you do this, it is critical that the foam be allowed to fully dry before reinserting it. Soak the foam filter in clean engine oil. Squeeze out the excess oil using a clean rag. If excess oil remains, it may cause the mower exhaust to emit unpleasant black smoke. Check the rubber gasket that seals the air filter to the carburetor. If the gasket has dried out or shows damage, it will need to be replaced. Put the filter back in place in the housing, then reattach the cover plate. Reconnect the spark plug wire and start the mower to test its operation.
