Power Units

Power sources for lawn and garden equipment fall into three categories: gasoline engines, electric motors and battery-powered electric motors.

For smaller equipment, the convenience of cordless operation is a major feature. Not only has extended battery life contributed to the popularity of cordless tools, but lightweight gasoline engines on products such as string trimmers allow users to move about freely without the fear of cutting an electrical cord.

Starting cordless units powered by electrical motors is easy, and battery charges will usually last through most typical yard jobs. The unit can be recharged between jobs. Increasingly, electric motors are being used in a wide range of outdoor power equipment and starter motor applications.

Larger power equipment is primarily gasoline powered.


Recoil starters are most widely used, but battery-powered starters have grown in use over the years.

The batteries for electric starters can be recharged either with chargers that connect to electrical wall outlets or with electrical chargers built into the engine, which recharge the battery while the engine is operating.

Battery voltage may be 6V or 12V, and the number of starts possible depends on the battery amperage rating and the output of the engine charger.

The convenience and reliability of electric starters are features. Electric starters may add $50 or more to the retail selling price of a walk-behind mower and as much as $150 to the price of a tractor.


Gasoline engines are available in two- and four-stroke cycle constructions. The four operating functions are intake, compression, power and exhaust stroke.

In two-cycle engines, compression and power are combined in one cycle, and exhaust and intake are the second cycle.

A four-cycle engine uses valves and a two-cycle engine utilizes intake and exhaust ports.

Lubrication for two-stroke cycle engines comes from the oil being mixed with the gasoline. The four-stroke cycle uses a reservoir.

Two-cycles are easy to start, but speed regulation is usually limited. Some models have fuel primers for easier starting.


Failure to use the correct plug, or substitution, could result in poor performance or engine failure.

Engine manufacturers specify spark plugs for specific requirements and best performance. Some of the considerations made in specifying spark plugs include heat range, size, sealing features, materials, depth projection (position of electrode) in the cylinder head and electrode shape/design.

Original equipment manufacturers can supply data on the specific plug needed for individual power equipment engines. Manufacturer representatives can also supply information such as charts and brochures on use and interchangeability.

Check your state and local codes before starting any project. Follow all safety precautions. Information in this document has been furnished by the North American Retail Hardware Association (NRHA) and associated contributors. Every effort has been made to ensure accuracy and safety. Neither NRHA, any contributor nor the retailer can be held responsible for damages or injuries resulting from the use of the information in this document.

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