When a lawnmower tears the grass, vibrates or won’t start, it’s usually no ‘mystery’. The cause is a blunt or bent blade, imbalance, fuel and the spark plug, the air filter, a flat battery on a cordless model or a safety switch. First, carry out a safe check at home. If there is strong vibration, an oil leak, sparks from cables or a suspected engine fault, stop mowing and take the machine in for servicing.

At Zakservices in Senica, we help owners of STIHL, MTD, WOLF-Garten, Cub Cadet, SUPA TECHNIKA and DAKR mowers tell minor maintenance apart from a fault that needs repairing in the workshop.

What you’ll learn in this article

what it means when a lawnmower tears instead of cutting
why it vibrates and when to stop immediately
basic diagnosis when it won’t start (petrol and cordless)
checking the spark plug, fuel, air filter and safety switches
when a fix at home is enough and when to go to the workshop in Senica
FAQ and contact details in Senica

Safety before every check

Switch off the engine and wait until the blade has stopped completely.
On a petrol model, disconnect the spark plug lead. On a cordless model, remove the battery.
Don’t tilt the lawnmower in a way that lets oil or fuel run into the filter or exhaust. Follow the manufacturer’s manual.
Wear gloves and sturdy footwear. The blade is sharp even when it ‘isn’t working’.
Never test the blade by hand with the ignition connected or the battery inserted.

When the lawnmower tears the grass (doesn’t cut cleanly)

You can recognise tearing by ragged, greyish or browning grass tips and by a lawn that looks frayed. The machine runs, but the cut isn’t clean.

The most common causes

Symptom	Common cause	What to try at home
Tears, engine runs fine	Blunt blade	Sharpen or replace the blade
Tears on one side of the cut	Bent blade or uneven ground	Check the blade is straight, workshop if it’s bent
Deck clogs	Wet / tall grass, blunt blade	Higher cutting height, cleaning, sharpening
Mulch is lumpy	Too much taken off at once	Mow in stages

Blunt or bent blade

A blunt blade is the most common culprit. We describe sharpening and balancing in detail in our article on blade sharpening. If the blade is bent, cracked or has a piece broken off, don’t sharpen it. Replace it. A bent blade often adds vibration too.

The same goes for STIHL, MTD and WOLF-Garten rotary mowers and for Cub Cadet or SUPA TECHNIKA cutting decks: the quality of the cut starts at the edge. On DAKR drum mowers, check the set of blades on the drum. Deal with worn or damaged blades as a set, depending on their condition.

More tips for a poor cut

Don’t use the lowest setting on tall, wet grass.
First cut it down on a higher setting, then fine-tune.
Clean caked-on grass out of the deck (with the power disconnected).
Check that the blade is the right way round and tightened as the manual says.

If it still tears with a sharp, straight blade and the engine sounds unusual, have the machine looked at in the workshop.

When the lawnmower vibrates

Slight vibration on an older machine may be down to a minor imbalance after sharpening. Strong vibration, knocking or the lawnmower ‘hopping’ across the ground are warning signs.

What to check

Blade: is it straight, free of chips and correctly tightened?
Balance: after sharpening, the blade must be balanced. Asymmetry = vibration and bearing wear.
Dirt: caked-on soil or string wrapped around the blade shifts its centre of gravity.
Mountings: loose blade bolts, a damaged blade adaptor or a cracked mounting.
Engine / deck: if you suspect damaged rubber mounts or a bent chassis, stop mowing.

When to stop immediately

Stop and take the machine to the workshop if:

the vibration is sudden and strong
you hear metal on metal or banging from the deck
the vibration remains after trying with a cleaned and tightened blade
you smell burning, oil is leaking or the engine is losing power in an unusual way

Strong vibration ruins bearings, the crankshaft and your comfort. It’s cheaper to stop early.

When the lawnmower won’t start (petrol)

STIHL, MTD and WOLF-Garten petrol lawnmowers and Cub Cadet or SUPA TECHNIKA ride-on mowers follow similar starting logic: fuel, spark, air, compression and safety switches.

Quick checklist

Tank and fuel: is there fresh fuel in the tank that’s suitable for the engine? Old fuel after months of storage often causes hard starting or no starting at all.
Primer / choke: as the manual says. Use the choke on a cold engine, but not always on a warm one.
Spark plug: disconnect it and check whether it’s flooded, heavily sooted or has a damaged electrode. A dry, clean spark plug with the correct gap is the foundation. If in doubt, replace it with a suitable type as the manual says.
Air filter: a clogged filter chokes the engine. Clean or replace it, depending on its condition and the manual.
Oil: check the level. Some machines have low-oil protection.
Safety switches: the drive lever / safety bar on the handle must be held down as the design requires. On Cub Cadet and SUPA TECHNIKA ride-on mowers, check the seat switch, the position of the gear lever and the brake switch as the manual says.
Flooded spark plug after several failed starts: let the engine air out as the manual says, replace or dry the spark plug, and don’t keep priming with fuel unnecessarily.

What not to try at home

Don’t spray random ‘starting’ sprays into the air intake without understanding the fire risk.
Don’t dismantle the carburettor if you don’t know the procedure and don’t have the parts.
Never leave the engine running in a closed garage.

If the engine fires and dies straight away, or only runs on choke, the problem is often the fuel system or a filter. At that point, we can sort it out at Zakservices faster and more safely than you could by trial and error.

When a cordless lawnmower won’t start

With STIHL cordless lawnmowers (and other cordless models in our range), start with the simple things:

Battery charge, and the battery correctly inserted in the machine.
Safety key / switch, depending on the model.
Contacts on the battery and machine: clean, dry, free of corrosion.
Overheating: some systems temporarily block operation. Let it cool down.
Blade jammed by grass or an object: remove the battery and clear the deck.
A second battery to test with, if you have one. If the second one works, the problem is more likely the first battery or the charging.

If the charger shows an error, the battery doesn’t hold its charge or the machine doesn’t respond even with a charged battery, bring both the battery and the machine to the workshop. Don’t take the battery pack apart.

DAKR drum mower: a short note

The same principles of safety and drive apply to DAKR machines. If the machine vibrates strongly, check the mounting and condition of the blades on the drum. Don’t replace damaged blades ‘by eye’ with an incomplete set if the manufacturer expects a balanced set. If the petrol engine won’t start, the points on fuel, spark plug and filter apply. If in doubt, choose the workshop rather than brute-force attempts.

Fix it at home or go to the workshop: a quick decision

You can manage at home (carefully):

sharpening and replacing a straight blade (after disconnecting the power)
cleaning the deck and the air filter
replacing the spark plug as the manual says
replacing old fuel with fresh
checking the battery, contacts and safety switches
tightening a loose blade using the correct procedure

Go to the Zakservices workshop in Senica:

strong or sudden vibration
a suspected bent shaft, damaged bearings, an oil leak
the engine won’t start after a basic check of the fuel, spark plug and filter
the cordless system reports errors, or the battery has lost a lot of capacity beyond normal ageing
a Cub Cadet / SUPA TECHNIKA ride-on mower with complex safety switches and electronics
any job where you’re unsure of the tightening torque or the manufacturer’s procedure

A practical 10-minute routine (as a guide)

Safely disconnect the power (spark plug or battery).
Look at the blade: sharp, straight, clean, tight?
Clear grass and foreign objects from the deck.
On a petrol model, check the fuel, filter and spark plug.
On a cordless model, check the charge, the contacts and the safety switch.
Try starting it as the manual says.
If the vibration or starting problem persists, stop and book a service.

This routine saves time for both you and us in the workshop. Often we can already tell over the phone whether it’s the blade, the fuel or something more serious.

Frequently asked questions

Why does the lawnmower tear the grass even though the engine runs?

Most often it’s a blunt or bent blade, cutting too low in tall, wet grass or a clogged deck. Start with the blade and the cutting height.

Is vibration after sharpening the blade normal?

It may feel slightly different, but strong vibration means poor balance or a bend. Balance or replace the blade. If the vibration persists, go to the workshop.

How often should I change the spark plug?

As a guide, follow the manufacturer’s manual and the plug’s condition (flooded, sooted, damaged electrode). With hard starting, replacing it is a cheap and quick step.

Can old fuel stop the engine starting?

Yes, very often. Fuel that has been standing for a long time loses quality and clogs the system. Before the season, it’s better to use fresh fuel and a clean filter.

My STIHL cordless lawnmower doesn’t respond. What should I check first?

Check the charge, that the battery is inserted correctly, the safety switch and whether the deck is blocked. Then try a second battery, if you have one.

When should I stop trying at home and come to Senica?

With strong vibration, an oil leak, a suspected damaged shaft, if a basic check of the fuel, spark plug and filter hasn’t helped, or if the cordless system shows errors.

Can you help with a Cub Cadet or SUPA TECHNIKA ride-on mower too?

Yes, depending on stock and the extent of the repair. Ride-on mowers have more safety switches. Keep home diagnosis to the basics and leave the rest to the workshop.

Where in Senica can I take a lawnmower that won’t start or vibrates?

At Zakservices. Describe the symptoms, the brand and what you’ve already tried. We’ll arrange an inspection and agree the next steps.

Let us help you at Zakservices in Senica

If your lawnmower tears the grass, vibrates or won’t start, you don’t have to guess. At Zakservices in Senica, we’ll check the blade, ignition, fuel system, filters and batteries on STIHL, MTD, WOLF-Garten, Cub Cadet, SUPA TECHNIKA and DAKR machines, depending on what our stock and workshop can offer at the time.

Zakservices, s.r.o.
Obchodná 493/2A, 905 01 Senica (white building opposite the Kaufland car park)
Phone: 0904 446 915, 034/651 7072
Email: zakservices@zakservices.sk
Website: https://zakservices.sk

Bring in the machine or give us a quick call first. We’ll tell you what’s worth trying at home and what’s best left to the workshop.

What to do when your lawnmower tears the grass, vibrates or won’t start