Why Some Small Engines Fail in a Few Years Rather than Decades

Many homeowners believe that the small engines in their household tools, like lawn mowers, pressure washers, generators, or pumps, simply wear out or fail due to regular use. This is a misconception. By following basic maintenance routines, you can extend the life of your small engine equipment to ten years or more, instead of just a few years, which is what happens when maintenance is neglected. Continue reading to learn about essential maintenance areas and the causes of preventable damage to your small engine, helping you to prolong its lifespan!

Overheating

Small engines run hotter than your automotive engine. In most smaller machines (unlike your automobile which relies on the cooling effects of coolant) small engines rely on the unobstructed flow of air for cooling. In short, an engine that runs hotter wears faster. The best way to ensure that your small engine is running cool, is to ensure that the cooling fins found on the cylinder head of the engine are free of dirt and other debris. This dirt and debris essentially packs in the damaging heat through an insulating effect. When the flywheel on the engine spins, it fans the engine by passing air over the cooling fins that are designed to dissipate heat. For lawn mowers as an example, remove your engine cover annually or sooner if operated in extreme conditions and ensure that there is no dirt build up on the flywheel cooling fins and the cylinder head cooling fins. Pro Tip: Avoid running a small engine without the engine cover installed for prolonged periods, as this my overheat the engine. The cooling air provided by the spinning flywheel is no longer contained within the engine cover if it is removed.

This is an example of an engine cover removed exposing the flywheel cooling fins underneath

Cylinder head cooling fins are shown here; their increased surface area dissipates heat

Abrasive Ingestion

Small engines are essentially air pumps. Air is needed for the engine to effectively fire. If the ingested air is dirty, and contains small particulates, these contaminants can wreck havoc on the internals of the engine. Air filters are designed to catch these fine particulates before they enter the engine. Always ensure your air filter is clean and properly installed. Pro Tip: If your small engine implement uses a foam filter it may be necessary to coat it in clean engine oil to ensure it actually catches fine abrasives. Refer to your owner's manual for details.

An example of a paper style air filter

Infrequent Oil Changes

Oil changes are necessary to prolong the life of your small engine equipment. Look to change your engine oil at least annually or every 25 hours of operation (or sooner depending on operating conditions). Oil lubricates, cools and provides anti-corrosive properties to internal engine parts. If neglected, contaminants can become suspended in the oil and it becomes"loaded" and must be changed. Pro Tip: Check the color and level of your oil prior to using your equipment. Oil with a black sludgy appearance warrants an oil change. Oil level that has suddenly risen and smells of gasoline indicates an oil dilution problem where gasoline is entering the crankcase. Simply changing the oil will not remedy this issue.

Lawn mower oil being changed

Engine oil dipstick with clean oil; its at the low mark and more needs to be added

Oil Dilution: Explained

The carburetor is the device responsible for providing your small engine with the correct mixture of air and fuel necessary to run. During repeated short runs where the engine never reaches operating temperature, a carburetor that is allowing too much fuel into the engine, flooding the engine due to over-priming or consistently running with the choke on can all contaminate the oil with gasoline. If you are unsure about how to use a choke refer to our post here: How to use a Choke: Mastering the Choke Function in Small Engine Operation. Diluted oil does not lubricate as well, accelerating friction and engine wear. Signs to look for are rising oil level on dipstick, gasoline smell on engine oil dipstick, watery thin appearance of oil and in some cases white smoke emitted from exhaust.

Impact Damage Due to Operator Error

Small engines are designed to handle steady operating loads, not abrupt sudden shock loads. Hitting an object with a lawn mower blade for instance or jamming a snow thrower's auger with ice transmits shocks through the internals of a small engine (crankshafts, bearings, engine mounts etc.) These forces can bend components that usually warrant an engine replacement, as the cost to repair may exceed the value of the entire unit.

Over speeding

When an engine runs faster than it was designed to it experiences significantly higher stresses that shorten its lifespan if run for prolonged periods in this condition. A governor is responsible for adjusting the engine RPM based on operating condition or load. An improperly adjusted governor or missing governor springs or linkages can cause an engine to exceed its safe RPM range. Pro Tip: If your equipment suddenly sounds much louder or noticeably higher pitched than usual, have the governor inspected before continuing to use it.

By following the above mentioned maintenance measures and practices, you can realistically expect your small engine implement engines to last for decades rather than just a few years.

Never the Norm!