Lowe's shows you how to tune up your walk-behind mower. Make a difference in how your motor starts by changing the spark plugs and cleaning the filter and lubricating when necessary. To do this you will need a drop cloth, a cleaning brush and work gloves, oil, spray lubricant, air filter and spark plug. Before performing any maintenance, read your owners manual. Ventilate your work area, protect the ground and remove the grass catchers. Disconnect the spark plug so your mower won't start. Lubricate all the moving parts. Make sure to clean up any excess oil.