Lawn mowers are tough pieces of machinery, but that certainly doesn’t mean they don’t need some TLC every now and again to keep them running in tip-top condition. Quality mowers will keep going for years if they’re looked after, so we’ve put together this handy guide to help you get the most out of what’s probably your most-used piece of garden machinery.

This guide has been broken down into three sections for your convenience. The first section deals with parts that you’ll find on almost all lawn mowers, and then you’ll find two other sections that cover electric and petrol mowers respectively.

General Mower Maintenance

Whether they’re push-driven, petrol powered or electric, most lawn mowers have a few common parts that require regular maintenance. Whenever possible, you should check the following things to ensure that you never run into issues:

Wheels

Wheels are easily forgotten (unless you have a hover mower of course!), but a quick check to make sure that they’re still in good shape will help make the job of pushing the mower up and down your lawn a little bit easier. If you need to, disassemble them and clean off any ingrained dirt that might be slowing them down. Lubricant can also work wonders if they’re a bit squeaky or don’t spin freely. Make sure none of them are loose either - loose a wheel and you could damage both your manicured lawn and the mower itself.

Fastenings

You really don’t want anything to come off while you’re in the middle of mowing your lawn, so it’s a good idea to periodically check all of the fastenings that you can see on the machine. Check that nuts and bolts are tight, and that any clips are still in good condition and doing their job. Proper storage of your mower will help with this, as moisture will encourage nuts and bolts to rust, and exposure to the elements will degrade plastics. Broken clips should be replaced, which may also mean replacing the panel, and overly rusted or rounded-off bolts should be changed too.

Blades

Blade maintenance will change slightly depending on what type of cutting method your mower uses, but the general aim is the same. The sharper the blades, the better they’ll cut, which means less strain on the machine, and a nicer looking lawn. Have a look under the cutting deck and inspect the blades carefully, whether they’re the rotary, cylindrical or flail type.

The major thing to look out for is anything misshapen. Rotary blades in particular are prone to being bent if they go over an object such as a stone, and trying to bend them back into shape is usually pointless - they should be replaced. Flail heads do tend to cope better with impact, but that doesn’t mean they’re immune either. Rust and general degradation of integrity is the other thing to be concerned about - this can’t be repaired and suspect blades should be replaced.

Fortunately, we supply a wide range of replacement blades if you discover that yours just isn’t doing the job any more. Get in touch if you aren’t exactly sure what you need.

If you’re sure that your blades are in generally good condition, but are simply a bit dull, then you can think about sharpening them if you’re DIY-minded. This can be done with a specialist sharpening tool, multi-purpose files, or an angle grinder. Take great care if you decide to go down this route, just as you would when handling any other type of blade.

Electric, Cordless and Battery-Powered Lawn Mower Maintenance

Most domestic gardeners will have some form of electric lawn mower, whether powered directly by the mains, or a battery. They are generally the lightest, most cost-effective and easy to deal with, and this extends to their maintenance too. You won’t need much specialist knowledge to keep your electric mower running well.

A word of caution first however. Mains power can be very dangerous indeed, so before you do anything at all, you must ensure that your mower is unplugged and switched off. If it’s battery powered, then the same applies - remove the battery before going anywhere near the motor or blades, and remove the safety key if it has one. If you’re in any doubt as to how to safely handle your electric mower, then again, leave it to an expert.

Air Flow

Cooling is vitally important with an electric motor - if it gets too hot then there’s every chance that it will burn out, which could be a very costly mistake. Fortunately it’s fairly easy to make sure that this doesn’t happen. Before you start mowing, clear away any obstructions such as grass and other debris from the vents, and if they build up in the process of mowing, stop and get rid of them. Start each mow with a completely clean machine.

Cord

Before you plug the cord into the mains, you should check the full length of it for any problems. Cuts and nicks can be common, and any exposed wiring should be dealt with before you start mowing. You should also place a lot of focus on each end of the cord, as stress can potentially damage where it meets the motor or plug. Repairing a standard UK plug is fairly straightforward, and there are plenty of guides available, but you may need expert help if there’s an internal motor problem.

Battery

Batteries can be costly to replace, so they should be well looked-after if you want to get a long life out of them. Different batteries will have differing requirements, so it’s always a good idea to check the manual if you’ve still got it. Lead-acid batteries for instance will degrade every time they’re fully discharged, and batteries without any kind of smart-charging system can be damaged if left charging when they’re at full capacity. Store in a dry location to prevent rust or excessive oxidation on the terminals.

Petrol Lawn Mower Maintenance

Petrol lawn mowers are more commonly found in the arsenal of professional gardeners or those with very large gardens to tend. They do require a little more thought when it comes to maintenance and running compared with their electric counterparts, but the benefit is that they’re much better at dealing with large areas because they can run longer with no cord. They’re also generally a lot more powerful and can cut through tough grass with ease.

As with electric mowers, safety is paramount. While you don’t need to be a mechanic to look after your machine, some basic knowledge about how a petrol engine works is important, and if you’re unsure, leave maintenance to the experts. Never attempt any kind of observation or repair while the engine is running, and leave your mower to cool before touching it too.

Another important rule of thumb is that you should never tip a petrol driven lawn mower on its side when performing maintenance, as this can cause oil from the sump to flow through into the machine’s silencer or, worse still, its air filter. Contaminating the air filter with oil can cause permanent damage to the air filter and also presents a fire risk, so, if you need to get to your mower’s underside, always tip it up from the front, so that the spark plug is pointing upwards.

Spark Plugs

Spark plugs are responsible for delivering an electric current to the ignition chamber on your mower’s engine and are one of the most common things to wear out on most petrol lawn mowers. If your mower is puttering upon start up, or the engine frequently fails to catch, it could well be because you need to clean or replace your spark plug.

To do this, first locate the spark plug (which normally protrudes slightly from the front of the engine) and remove the spark plug lead; a black cable that links the spark plug itself to the engine above.

You can then carefully tease the spark plug from its mounting, taking care to clean around the socket to ensure that loosened debris does not fall into the ignition chamber. Once this is done, carefully inspect the spark plug for contamination and/or the buildup of unwanted gunk, and decide whether you want to clean or replace the part.

In general, loose debris that can be rubbed off with a soft cloth and some spray-on plug cleaner should be removed by hand. Anything more stubborn and we would advise simply replacing the part, which can generally be done for under £10.

If fitting a new spark plug, make sure you use a spark plug gauge or spacer to get the correct gap between the plug and the electrode at the bottom of its mounting (your owner's manual should specify this). Once you’ve got the right gap, simply screw the new plug in - taking care not to over-tighten - and re-attach the lead.  

Oil

Clean and uncontaminated oil plays a vital part in allowing your petrol mower to run, and forgetting to regularly change it opens you up to the risk of engine seizures. As such, it is very important that you drain and refill your mower’s oil reserve:

  • After every 50 hours of use

  • At the end of the mowing season

  • After extended periods of protracted/heavy use

If you want to check the condition of your mower’s oil, simply locate the oil filler cap, unscrew, and use the dipstick provided to obtain a small sample, which you can inspect for excessive contamination. You are looking for the same tawny/golden colour as fresh oil and if significant discolouration is present, you should look to change the oil as soon as possible.

Note: If your mower does not have a dipstick, you can just dip an inch or so of cloth into the oil filler cap to check the condition of your oil.

To change the oil in your mower, you’ll first need to tilt the mower up so that its underside is exposed - taking creat care to tip it from the front and not the side so that oil cannot flow into other areas of the engine, and foul your air filter.

If you look underneath, you should then be able to locate the oil drain plug, which will be located below the centerline of the crankshaft (refer to your user’s manual for diagrams).

Once you have located, use a socket wrench or adjustable wrench to remove the plug and drain the oil into a container for disposal in accordance to local council guidelines. Once this is done, carefully wipe the area around the plug to remove debris and build-up, then replace the oil drain plug.  

You can now refill the oil reservoir through the oil filler cap, which will be clearly labelled in the user manual. If your mower has an oil filter, you may also want to inspect and replace this part while performing an oil change, dependant on the level of contamination encountered. Once you’ve replaced the oil in your mower, always allow the machine to run for a few minutes so that you can check for leaks.

Air Filter

Air filters stop contaminants and dirt from reaching the combustion chamber in your mower’s engine, and need to be replaced annually in order to prevent your engine from getting fouled. Most mowers use a paper filter, which is very easy to change; simply locate the filter bay on your engine using the owner’s manual, loosen the screw or fastener that keeps it closed and open the cover. You should then be able to reach in and remove the filter.

At this point, you should inspect your mower’s air filter to decide whether it needs to be replaced or not. If it is dirty, or shows signs of severe discolouration, it is time to install a new one using the reverse of the method outlined above; placing the cartridge into the bay, closing the cover and then re-tightening the screw.

If your mower has a foam filter, you will need to remove the filter from its housing, take the new filter, soak it in engine oil (which helps it to catch particles of dirt) wrap it in tissue and squeeze dry, then re-insert into the bay. More detailed instructions are normally provided with the filters and/or can be found in the owner’s handbook, and the procedure is relatively straight forward as long as you pay attention to the directions given.

Foam filters can be doused in a cleaning solution and re-used, although we wouldn’t advise this as a second-hand filter is rarely as effective as a fresh one.

If you have any problems with the guidelines outlined here, or would like specific advice on maintaining your lawn mower, you should always consult a local repair/service professional, and remember to check your warranty before undertaking a service, as you can violate some warranties by opening/tampering with parts of a mower’s engine.