Troubleshooting · Updated May 2026
Common Mower Problems & Fixes
Before you take it to a repair shop or buy a new one, most mower problems have a simple fix you can do in the shed.
Mower won't start
Cordless
- Check the battery is fully clicked in - a half-seated battery is the most common cause
- Try the battery in another tool to confirm it holds charge
- Check the safety lever (bail arm) is fully engaged - most mowers won't start without it
- Inspect the battery contacts for corrosion and clean with a dry cloth
Petrol
- Check there's fresh fuel in the tank (fuel older than 30 days can go stale)
- Check the spark plug - remove it, clean or replace (£3-£5 from Screwfix)
- Check the air filter - a clogged filter starves the engine of air
- Prime the engine (3 presses on the primer bulb) and set the choke to 'start'
Mower cuts unevenly
- Dull blade - the most common cause. Sharpen it
- Uneven wheels - check all four wheels are at the same height setting
- Bent blade - remove and check on a flat surface. Replace if bent
- Clogged deck - scrape dried grass from the underside
Mower stalls on wet or long grass
Raise the cut height for the first pass - trying to take 5 cm off in one go overwhelms most mowers. On wet grass, mow slowly and make narrower passes. If a cordless mower keeps cutting out, the motor protection is kicking in - let it cool for 5 minutes and try again with a higher cut.
Battery draining too fast (cordless)
- Battery age - after 500+ cycles, capacity drops noticeably
- Dull blade - the motor works harder to turn a dull blade, draining the battery faster
- Grass too long - raise the height setting
- Extreme cold - lithium-ion batteries lose 10-20% capacity below 5°C
Excessive vibration
Usually a bent or unbalanced blade. Remove the blade, check it's straight on a flat surface, and check the balance. If the blade is straight but vibration persists, the crankshaft may be bent (common after hitting a rock) - that's a repair-shop job.
Still stuck?
Most UK mower brands have phone support lines that are genuinely helpful. Bosch, Ryobi and Gtech all offer free troubleshooting calls. For petrol mowers, your local garden machinery dealer can diagnose most issues for £20-£30.