Tips for Maintaining Small Engines at Home


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Small engines provide power for many outdoor machines, such as lawn mowers, grass cutters, generators, and light vehicles like mopeds. They are called “small” as they usually pack less than 25 horsepower but are still powerful enough for the equipment they are intended for.

Tips for Maintaining Small Engines at Home

If you own a piece of machinery that has one, it pays to have basic knowledge of small engine maintenance to save yourself from headache, expense, and downtime when your machine breaks down. After all, such engines are pretty straightforward, so tinkering with them isn’t as scary or complex as some may think.

Read the Manual (and Keep It Accessible)

As many compact machines share the same design and features, people often assume they know exactly how to operate and maintain such, but that is sometimes not the case. Different makes, models, and specifications may have different needs.

Upon purchasing a piece of equipment, read the manual carefully to understand its proper operation and maintenance. You might need to use it a little differently from your old one, or perhaps it needs another kind of spark plug or fuel. Keep the manual in an accessible place for future reference.

Use Fresh Fuel Only

Yes, gasoline “expires,” so storing it in containers at home as a reserve can be a bad idea (unless you are a heavy user or have multiple machines). Regular gas has a shelf life of three to six months. For ethanol-blended variants, it can be less than three months. Stale gas can cause a host of problems to any engine, such as hard start-up, loss of power, poor fuel economy, and damage to internal parts.

As much as possible, fill your equipment with fresh gas from the pump the day you need it. Good fuel will maximize your engine’s performance and help prolong its service life.

Drain the Fuel Tank When Storing Equipment for Long Periods

If you plan to put the machine in storage for over two months (especially during winter), drain the fuel to prevent it from going stale inside your engine. Stale gas left for months inside your machine can gum up and clog the carburetor and other components.

To drain your tank, you can use a siphon pump to transfer the gas to a petrol can. If the fuel is still relatively fresh, you can use it for other equipment (like your generator). Else, bring it to a gasoline recycling facility or a hazardous waste disposal center near you so it can be safely discarded or repurposed.

Alternatively, you can incorporate a fuel stabilizer with the surplus gas before storing your equipment to help prevent the fuel from degrading. This practice will save you time and effort, especially when it’s time to take out the machine and use it again.

Check Oil Level and Quality

Just like in your car, oil is one of the most important things to check in your small engine. As oil can burn off little by little over time, you need to see if there is still enough left inside.

To inspect the oil, remove the dipstick, wipe the oil at the tip, and put the stick back in. Pull it out again to see the oil level at the indicator. If it’s in between the two lines or holes, you are good. Conversely, you should top up if it is lower than the bottom line/hole. Aside from the level, you should also inspect the oil’s color. If it’s very dark already, replace it immediately.

As a rule of thumb, the oil in a small engine should be changed every 50 hours of use or once a year, whichever comes first. As always, use the oil type recommended by the manufacturer (as stated in the manual).

Change the Air Filter As Needed

Clean air is essential to the combustion process. To keep the flow of good air into the engine, make sure the air filter is not full of dirt and debris. Replace the air filter as stated in the user manual or as you see fit. Avoid cleaning the filter with compressed air, as doing so can damage it.

Check the Battery and Its Connections

Watch out for corroded battery terminals. Use a brush, some baking soda, and a splash of water to remove corrosion.

If you have a multimeter, check the voltage output of the battery. If the reading is lower than 12.6 volts, it’s time to get a new one.

Inspect the Spark Plug

It is a good idea to check the spark plug when you change the oil. Remove it and have a look. If the electrodes look brownish, clean them with a wire brush, and measure the gap with a feeler gauge. If the electrodes are spaced farther or closer than recommended (see the manual), bend the ground electrode in the appropriate direction to achieve the desired gap. Put the plug back in and fire up the engine to try.

If the spark plug shows any signs of deterioration, replace it with a new one. Most lawn mower manufacturers recommend changing the plug once a season.

Following these tips can help keep your small engine running well for the years to come. For any problems that seem daunting to DIY, contact a qualified technician.


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