Maintaining a Lawnmower for Spring Growth

Why Spring Servicing Matters More Than You Think

By the time the first proper warm spell arrives, grass in most of the UK can put on a centimetre or more a day. That means the mower you parked in the shed last October is about to be asked to work harder than it has all year. A machine that starts reluctantly in April will only get more stubborn once the growth really kicks in, and a dull blade tears grass rather than cutting it cleanly, leaving yellowed tips and a lawn that looks tired within days.

The good news is that a full spring service takes an hour or two and costs very little. Do it on a dry, mild afternoon before the growing season begins in earnest, and you will spend the rest of spring cutting rather than tinkering. For petrol mowers, always work with the machine off, the spark plug lead disconnected, and the fuel cap loosened or the tank drained if you are tipping the mower on its side.

Start With the Air Filter

The air filter is the most overlooked component on any petrol mower, and a clogged one is behind a surprising number of rough-running, hard-to-start engines. Dust, dried grass clippings and last year's pollen all collect in the foam or paper element, choking the engine of the air it needs.

• Foam filters: wash in warm soapy water, squeeze gently (never wring), let them dry completely, then re-oil lightly with a few drops of engine oil and work it through.
• Paper filters: tap them out against a hard surface to dislodge dust. If they look grey, oily or torn, replace them — they cannot be washed.
• Check the housing: wipe out any debris sitting behind the filter, or it will simply be drawn straight back in.

If you cut in dusty or very dry conditions, check the filter again mid-season. It is a two-minute job that protects the engine's whole breathing system.

Oil: Level, Colour and Consistency

Four-stroke mowers need their oil checked before the first cut, not after. Stand the mower on level ground, remove the dipstick or filler cap, wipe it clean, screw it back in and check the level. It should sit between the marks — not above, since overfilling causes smoking and seal damage.

Look at the colour while you are there. Fresh oil is amber and translucent; oil that comes out black and thin, or that smells strongly of petrol, has done its time. A seasonal oil change is cheap insurance, and most domestic mowers take around 0.5 to 0.6 litres of SAE 30 or 10W-30, depending on the manual. If you have never changed it, tip the mower towards the filler side, drain into a suitable container, refill, and take the old oil to your local household recycling centre.

Two-stroke machines are different: they rely on a correctly mixed petrol and oil ratio, usually 50:1, and do not have a separate sump to check.

Sharpen the Blades Before the Grass Starts Growing

A sharp blade is the single biggest improvement you can make to how your lawn looks. Blunt blades bruise and shred the grass, and the damaged tips turn brown and become vulnerable to disease. You will also notice the mower labouring, especially in longer or wetter grass.

• Disconnect the spark plug lead before you go anywhere near the blade.
• Tip the mower onto its side with the air filter and carburettor facing upwards, so oil does not flood the engine.
• Use a spanner to remove the blade bolt — it is usually a left-hand thread, so turn it clockwise to loosen.
• Sharpen with a flat file or a bench grinder, following the existing angle at roughly 30 degrees. Take off only a little metal, and keep the blade balanced.
• Replace the blade if it is badly nicked, bent, or worn thin at the tips. A new blade costs less than a ruined lawn.

Check the blade bolt and washer for wear while the blade is off, and tighten everything to the torque setting in your manual — a blade that works loose is genuinely dangerous.

Spark Plugs, Fuel and the First Start

A tired spark plug causes misfires, poor starting and wasted fuel. Remove it with the correct plug spanner and inspect the electrode: light brown is healthy, black and sooty means a rich mixture, and oily deposits suggest worn rings or too much oil. Gap it to the manufacturer's specification, usually around 0.7 to 0.8mm, or simply fit a new one — they are inexpensive and worth renewing every season.

Old petrol is another common culprit. Fuel left in the tank over winter can go stale in as little as a month, and ethanol-blended petrol attracts moisture. Drain last year's fuel into a suitable container, refill with fresh petrol, and consider adding a fuel stabiliser if you do not expect to use the mower regularly.

Once everything is back together, check the cables and throttle lever move freely, top up the fuel, reconnect the spark plug and start the engine on a hard surface. Let it run for a minute, listen for any unusual knocking, and check for leaks. Then you are ready: set the cutting height a notch higher than you would in midsummer for that first cut, and enjoy the sound of a machine that is ready for the season ahead.