Whether it’s a small ornamental lawn or a lush multi-purpose lawn – the lawn mower helps to regularly cut back the cultivated and tended area for dense and even growth. But even the best device causes problems from time to time. With a lawnmower, the first sign of a serious problem is often a fluctuating speed. Find out why and what you can do here.
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That’s why the lawn mower runs rough
Ultimately, there are only a few factors that can cause an engine to run smoothly. The causes of a fluctuating speed, on the other hand, are far more diverse.
The clogged air filter
A predefined quantity of oxygen and therefore also air supplied from outside is required for even combustion of the gasoline. If the supplied oxygen fluctuates, the speed will drop with the amount of air supplied and the engine will run roughly.
- Causes: Dirty, clogged air filter
- eg due to sucked-in dust and grass residue
- Remedy: open and clean the filter,
- Blow out the disposable filter (paper filter) with compressed air or knock it out as a temporary immediate measure
- replace in the long run
A clogged carburetor
In addition to dirt, which is carried to the carburettor by defective air filters, other foreign matter can also lead to this heart of every simple petrol engine no longer working reliably. If the ratio of petrol to air fluctuates, the speed also fluctuates and the entire system of intake, combustion and exhaust emissions runs unevenly.
- Causes: Dirt, dust or oil in the carburetor chamber
- resulting in impaired float and needle function
- Remedy: Remove and clean the carburetor
Incorrect settings
A lawn mower will also run roughly if the carburettor settings are not correct. Normally, the fuel-air mixture can be adjusted so that it is sufficient for the respective requirements. If incorrect specifications are made here, it may be that there is either too little fuel or too little air for a smooth run. As a result, the engine does not stop immediately, but it can be noticeable through large speed fluctuations.
- Causes: Incorrect carburettor setting
- Remedy: Adjust according to the manual
Mechanical defects
The classic carburettor is regulated mechanically. Regardless of whether it is the connection from the throttle lever to the carburetor or its internal mechanics, the lawnmower will run rough if bent, stiff or broken components no longer function reliably.
- Causes: technical defects or damage during transport or operation
- Remedy: Replace or repair defective parts
- In the event of heavy soiling and adhesions, first clean and check for damage
lack of fuel
If the petrol is running low, the flow from the tank into the carburetor may be temporarily reduced due to petrol sloshing in the tank and air bubbles forming. The result is an uneven run until the fuel finally runs out completely.
- Causes: The fuel level in the tank is too low
- Remedy: refuel
The spark plugs
The proverbial igniting spark is the be-all and end-all of every combustion engine. If the spark plug can no longer perform this reliably, the regular ignition process is disrupted and the engine literally gets out of step.
- Causes: worn, heavily soiled or damaged spark plugs
- Remedy: Clean spark plug and replace if necessary
Impediments to the running of the knives
In lawn mowers, the blade is directly connected to the engine. The engine runs rough when the blades do. Reasons for this can be defects, but also simply wear and tear. As soon as a blade no longer cuts through the grass cleanly, it is slowed down by the increased effort required to tear off the grass, which ultimately also affects the engine speed.
- Causes: blunt knives, damage to the knife shaft
- Remedy: Regrind or replace knives, rectify any defects identified
Customer service instead of trying it out
Even the most experienced hobby gardener will not be able to identify and eliminate every cause for a fluctuating speed of the lawnmower. When the point has come that all obvious causes have already been ruled out, it is worth going to the specialist. Although there is a certain probability of finding a fault through trial and error and further searching, on the other hand there is at least as great a risk that further damage will be caused by improper repair attempts instead of eliminating the existing problems.
