How to Keep the Engines In Your Equipment from Overheating

engine overheatingWhether it’s in a V-twin in a mower or a two-stroke in a string trimmer, the engines in your outdoor equipment can overheat when subjected to extreme summer temperatures. Left unchecked, metal parts will expand, increasing wear and possibly seizing, requiring a pricey rebuild. These tips will help you keep your equipment cool, extending the life of their engines.


Most small engines are air-cooled. They use fins on the cylinder head and block provide the surface area needed to transfer heat from the engine to the outside air. As you use your equipment, these fins get covered in dirt. This reduces their ability to shed heat, increasing engine temperatures.

To remove dirt and dust, wipe down the fins with a stiff brush or a cloth to remove build-up. Never use water when cleaning your engine: it can get inside, causing rust and possibly hydro-locking. Some Kawasaki V-Twins have inspection/clean-out ports built into the cowling. Blowing compressed air through these ports cleans the cylinders.

Liquid-cooled engines transfer heat to coolant which passes through a radiator. This radiator has small metal fins that transfer heat to the air, just like an air-cooled engine. Kohler recommends cleaning the radiator on their Aegis engines every 100 hours of operation. They make cleaning kits that can reach the entire radiator without having to remove parts from the engine.

Air Flow

An air-cooled engine in a motorcycle sits out in the open, taking advantage of the bike’s high speeds to keep cool. The engines on your lawn equipment move slowly, and generators don’t move at all. This requires an alternate way to get air.

If you look into the screen on the front or top of your engine, you’ll see the flywheel is covered in small fins. It acts as a cage fan when the engine is running, drawing in air and pushing it across the surface of the engine. The cowling isn’t just there for looks: It helps direct this air.

To work effectively, the screen needs to be clear of grass and debris, while the cowling needs to be clean and intact.


Motor oil doesn’t just lubricate the engine, it helps transfer heat from the combustion chamber to the rest of the head and block. This helps the cooling system has an easier time removing it from the engine.

Air-cooled engines get a lot hotter than liquid-cooled engines. With the added stress of summer heat, this can burn off low viscosity conventional oils. To combat this, most manufacturers recommend using either a heavier oil or a synthetic at higher temperatures.

– Briggs & Stratton and Vanguard recommends checking the oil in their engines frequently if they’re used with 10W30 or SAE30 above 80°F due to increased oil consumption. Switching to a 5W20 synthetic or their 15W50 synthetic oil prevents oil burning at high operating temperatures.

– Honda recommends 10W30 in most of their engines for all temperature ranges.

– Subaru recommends 10W40 in their single cylinder engines.

– Kawasaki recommends 10W40 up to 100°F and 20W50 up to 115°F.

All commercial duty and high-end consumer engines made today have sensors that cut the ignition if the oil level is too low. However, it’s good practice on any engine to check the oil level before startup.


The Kohler Aegis uses a liquid cooling system for better performance over a wide range of temperatures. Like the engine in your car, it needs the right amount of clean, fresh coolant to manage engine temperatures.

Before using your Aegis-powered equipment, check the overflow tank behind the radiator. Add coolant if the level is below the “Add” mark.

Kohler recommends changing the coolant in their Aegis engines every two years or 1,000 hours of operation.


If the engine doesn’t get enough fuel, combustion chamber temperatures will skyrocket. A lean fuel mixture will leave a white, ashy film on spark plugs.

While bad seals on the carburetor can lean out the fuel mixture, most problems are caused by needle jets clogged by stale fuel. Fuel injected engines are less susceptible to fuel issues, but both Vanguard and Kohler still recommend using a fuel stabilizer with their engines.

When it comes to two strokes, getting the right ratio of fuel to oil is critical. Using too much oil won’t improve lubrication, but it will lean out the air/fuel mixture. This leads to rapid overheating that will shorten the engine’s life.

We Can Help Your Equipment Keep Its Cool

When you need parts, service or replacements for anything you use for landscaping, visit Shank’s Lawn Equipment. We’re an authorized dealer for a wide range of equipment and small engine manufacturers including Briggs & Stratton, Honda Engines, Subaru Industrial Power and Kohler Engines. Visit our shop at

We also ship parts and accessories across the U.S. and Canada. To order, visit

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