General gardening topics

How to Maintain and Service Your Petrol Lawnmower Correctly

Last updated on February 11th, 2022

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Below the video, we have a step by step guide on how to maintain a petrol lawnmower in easy steps.

Petrol lawnmowers take a serious beating, especially if used for professional use, yet they are easy to neglect, perhaps until something breaks or you have trouble getting the engine to start, which is usually the first problem that arises from not servicing your mower correctly. Proper lawnmower maintenance can allow you to get the most out of your lawnmower and keep it performing for many years. You don’t need to be a mechanic to service your lawnmower; follow the following tips to maintain your lawnmower will keep it in tip-top shape and ensure your mower starts every time.

Below is a good video on how to maintain a petrol lawnmower

Read the owner’s manual and check the warranty information

A very important step, especially when dealing with intricate machines such as petrol lawnmowers is to have a read of the owner’s manual and the warranty information. The owner’s manual informs you of the best way to maintain your lawnmower as intended by the manufacturer. Most people skip this simple step even though they often have the essential, yet basic maintenance information in them. Most petrol lawnmowers need to be properly maintained to keep the warranty valid, some manufacturers insist you send it to be serviced once a year by a professional company while other manufacturers are happy for you to maintain your own mower if you know how and are competent.

Drain the petrol at the end of each season

Lawnmower experts claim that old petrol is a major culprit when the machine won’t start and they’re probably right. Therefore, make sure you drain any remaining petrol out of the machine at the end of every mowing season, and always use fresh petrol the following season. It may be easier to use the mower until the fuel runs dry to make things easier.

Check oil level and keep it topped up

Your mower should have the correct amount of oil as indicated by your mower’s dipstick. Look for signs of oil contamination, such as floating debris or degrading oil – oil that looks charcoal black. Contaminated or old oil should be drained out and replaced by the manufacturers recommended new oil.

To drain the oil, remove the drain plug (if your mower has one) and let it drain to the last bit. If your lawnmower doesn’t feature a drain plug, remove the filler plug, carefully tilt the machine to one side, and drain used oil via the fill hole. Another way to drain your mower is by using a siphoning syringe. Remove the dipstick, stick the syringe into the bottom of the oil tank and pull it up to draw oil from the mower.

Bear in mind that lawnmowers require a specific oil type, and again this is where the user manual becomes a point of reference. Only 4 stroke petrol mowers have a separate oil tank because the 2-stroke mowers have the oil mixed with the fuel so this step can be missed.

Clean under the mower deck and always disconnect the spark plug first

Grass build-up in the undercarriage is inevitable. If left unattended, grass can clog the lawnmower’s discharge chute and affect normal operation. Scrape any grass clippings and soil from the undercarriage using a wire brush and spray away any stubborn residue with a garden hose. Some mowers even have an attachment where you can connect a hose to rinse the underneath the mower deck. Actually, this should be part of your regular mower maintenance. Cleaning the undercarriage after every service can prevent any onset of rust on steel parts.

When cleaning the undercarriage, be sure to keep the air filter facing upwards so that dirt and oil don’t pour into it. In addition, always disconnect the spark plug before cleaning the undercarriage. There’s a chance you could start the engine up and have the blade spinning, which is obviously very dangerous. Just unclick the coil from the spark plug and it will simply pull off.

Check and clean the air filter

The air filter stops any dirt or debris from reaching the carburetor and mower’s engine, so this vital component should never be overlooked. These air filters are very easy to remove and clean so there are no excuses. Air filters need swapping each year and that shouldn’t be a problem because they are cheap to purchase. The area holding the filter is easily accessible and should be cleaned as well at the time of replacement. Replacing the air filter ensures optimal performance throughout the life of the mower. Some air filters can simply be cleaned with soapy water instead of replacing them.

Inspect the spark plug to keep it starting first time

A clean spark plug ensures quick starting, smooth running as well as preventing stalling and overheating. The spark plug is also an inexpensive component and would ideally be replaced yearly. Remove the spark plug with a socket wrench and install a new plug without tightening it too much. An overly tight plug could prevent the mower from starting and cause issues when trying to remove it at a later date. Add some oil around the thread of the plug for easy removal next time.

Briggs and Stratton have a good guide on cleaning a spark plug which you can read here.

Sharpen the blade to ensure the best cut possible

The blade is the most worked part of the mower. It undergoes a great deal of stress from rocks and hard branches. A dull blade should be removed and sharpened or even replaced. To remove the blade, on most mowers simply undo the centre bolt and safely pull the blade off. Make sure to wear heavy-duty gloves before handling the blade. You can sharpen the blade with a vice and metal file or use the service of your local mower shop for a small fee.

That’s it. Once you’ve completed these steps, your mower is ready for another season. A professional tune-up once in a while is also worth it for precise diagnostic tests to check the engine over in more detail. However, with the basic maintenance as described above, this may probably not even need doing.

Welcome to my site, my name is John and I have been lucky enough to work in horticultural nurseries for over 15 years in the UK. As the founder and editor as well as researcher, I have a City & Guilds Horticultural Qualifications which I proudly display on our About us page. I now work full time on this website where I review the very best gardening products and tools and write reliable gardening guides. Behind this site is an actual real person who has worked and has experience with the types of products we review as well as years of knowledge on the topics we cover from actual experience. You can reach out to me at

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