How To Service A Petrol Lawnmower

Written By: Archie Rich | Updated:
How To Service A Petrol Lawnmower
Archie Rich/DIY Works

Whether you own a premium or budget machine, the techniques used to service a petrol lawnmower should apply to the majority of models. If you have experience servicing cars, motorbikes or other petrol-powered machines, servicing your lawnmower is just as simple. However, if it’s your first time, below is our guide to servicing a petrol lawnmower.

What You’ll Need

  • Lawnmower oil
  • Oil drain pan or extractor
  • Screwdriver
  • Spark plug
  • Air filter
  • Petrol
  • Tissue paper
  • Flat file or angle grinder
  • Wrench & socket (removal of spark plugs)

How To Service A Petrol Lawnmower

1. Replace The Air Filter

To begin servicing your petrol lawnmower, replacing the air filter is a good place to start. The filter itself is usually located near the top of the engine and it’ll be contained within a plastic (or sometimes metal) cover.

To remove the cover, unscrew the bolts or pull off the snap fittings, which will then allow you to lift the cover off. With the cover removed, you should be greeted by the air filter, which can be pulled out and replaced with your new filter. After you’ve completed the replacement, make sure the filter is fixed securely in place and the cover is secured back on top.

2. Change The Oil

If the oil within your petrol lawnmower is over a year old, it’s advised that you replace it. In terms of the oil that you should use, it needs to be a specific lawnmower oil (as shown in the picture) and it must be a certain viscosity level that’s suitable for the engine. The required viscosity level and specification should be stated within your user handbook.

To begin changing the oil, you’ll first need to drain the existing oil out of the lawnmower. This can be achieved by tipping the lawnmower onto its side and draining the oil into a suitable drain pan or by using an oil extractor.

Once the old oil has been removed, you can proceed to add the correct oil to the lawnmower. You’ll want to fill it up with the new oil until its reached the correct marker on the dipstick.

Petrol Lawnmower Servicing
Archie Rich/DIY Works
How To Service Petrol Lawnmower
Archie Rich/DIY Works

3. Replace The Spark Plug

Every petrol lawnmower will have a spark plug and it’s often the part that gets forgotten about when it’s time to service your lawnmower. We believe that it’s “forgotten about” because most people think that it’s difficult to replace but it’s actually quite simple.

The spark plug is normally located at the front of the mower and it’s accessible by pulling off the HT cap (as shown in the below photo). With the cap removed, you can proceed to remove the spark plug by using a long-reach socket and wrench and turning it anti-clockwise. Once you’ve removed the old spark plug, insert the new spark plug and tighten it by hand so that it won’t cross thread. You can then proceed to tightening it with your wrench and reattaching the HT cap.

How To Service Lawnmower
Archie Rich/DIY Works
How To Service A Lawnmower
Archie Rich/DIY Works

4. Check The Controls

To operate a lawnmower, the controls must be fully functioning. These controls come in the form of a lever that’s pressed against the handle and a second lever for self-propelled models that controls the forward movement.

Therefore, as part of the service of your petrol lawnmower, you’ll want to ensure the controls are moving freely. You can ensure that this is the case by lubricating the joints with a suitable grease (such as WD40) to ensure there is no resistance.

5. Check The Blades

Even if you owned the best petrol lawnmower on the market, if the blades are blunt or damaged, it isn’t going to do a great job at cutting your lawn. Therefore, it’s crucial that you take the time to check the blades over.

If you notice that any of the blades are damaged or look blunt, you can sharpen them using a flat file or angle grinder. Whilst you are sharpening the blades, it’s crucial that you maintain the appropriate cutting angle. However, if this is something you don’t want to do, there are many professionals that’ll be able to sharpen your lawnmower blades.

How To Service A Petrol Lawn Mower
Archie Rich/DIY Works

Whilst you have access to the underneath of your lawnmower, it’s good practice to clear out any debris. The best way of doing this is to use water and a steel brush until the majority of dirt and debris is cleared.

6. Add Fresh Petrol To The Tank

Depending upon how long the lawnmower has been in storage, it’s advised that you drain the fuel tank and fill it with fresh petrol. This’ll eliminate any bad fuelling issues that may lead to the engine failing to start or misfiring.

7. Clean The Lawnmower

Although optional, cleaning the lawnmower of any debris is recommended because grass cuttings, leaves and other garden debris can find itself caught in all sorts of places.

For example, debris near the petrol filler cap (as shown in the photo below) has the potential to fall into the tank when it’s next open. The debris that’s near the motor can also find its way into the engine too.

Depending upon the time you have available, you can even give it a quick clean because you may be surprised to just how well it actually comes up with all the dirt and debris removed.

Petrol Mower Servicing
Archie Rich/DIY Works


Hopefully our guide on how to service a petrol lawnmower has given you the confidence to give it a go yourself.

Although there are several steps, it really is quite straightforward and it gives you plenty of satisfaction when you hear your petrol-powered lawnmower running smoothly. Ideally, you’ll want to service your petrol lawnmower once a year and before you begin to use it after it has been in storage during the winter.

If you feel that you need further help with regards to servicing your lawnmower, feel free to get in touch and we will try to provide our assistance where possible.

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