How Does a Self-Propelled Lawn Mower Work?

Self-propelled lawn motors are run by internal combustion engines. These engines usually have one cylinder and run on gasoline. Most self-propelled lawn mowers require a manual pull crank to start the carburetor.

How Does a Self-Propelled Lawn Mower Work?

Internal Combustion Engines

The majority of self-propelled lawn mowers are rotary mowers. They feature a blade that rotates around a vertical axis. Therefore, the blade spins horizontally. The mower sucks the grass up into the blade, and the blade rips the top off of the grass.

The Bar

Self-propelled lawn mowers will not cut grass unless the person behind the mower squeezes a bar, which is usually near the handle of the mower. The bar then engages the mower blade, and the lawn mower will move forward. Releasing the bar will cause the blade to stop rotating. In some of the more expensive self-propelled mowers, the driver will not shut off even though the blade has stopped moving, which means you can move the mower from one location to another without having to restart it.


Self-propelled lawn mowers are lighter and easier to maneuver, which makes it tempting for parents to let their children more the lawn. This is not a good idea, however. Rotary mower blades spin about 3,000 times all the way around each minute. In fact, around 30,000 people are injured by rotary lawn mowers every year, as reported by the American College of Foot and Ankle Surgeons.

Those same blades can also throw out debris with tremendous force such as rocks, sticks, toys or other large items. For that reason, not only should children not be allowed to use a rotary mower, but they should not be in the area when one is being used.

April Sanders

April Sanders is a writer, teacher and the mother of three boys. Raised on an organic farm, she is an avid gardener and believes that good growth starts with a rich, supportive foundation -- a philosophy that serves her well in both gardening and teaching. Sanders has written for Nickelodeon, Warner Brothers, Smarted Balanced, PARCC and others.