For many hobby gardeners, it is not just a job to be done, but much more a satisfaction to start the lawnmower and trim the lovingly tended lawn to a uniform length. It is all the more annoying when the lawnmower engine stutters instead of the usual sonorous hum of the single cylinder. However, with knowledge of the causes, unwanted stuttering can in many cases be easily remedied by yourself. We explain how.
Table of Contents
Common reasons for stuttering lawn mowers
While a number of causes can be the cause of a fluctuating speed , it is comparatively simple when the engine stutters. The ignition misfires that cause the stuttering are due to poor combustion of the fuel-air mixture in the cylinder. Ultimately, three main reasons can be responsible for this:
- Incorrect amount of fuel
2. Incorrect amount of air
3. Poor ignition
However, the search for the cause becomes somewhat more diverse if you want to transfer this manageable number of causes to the real lawn mower standing in front of it. Because while the reason for the stuttering may be one and the same, many aspects can lead to the fact that, for example, the amount of fuel does not correspond to the target. Therefore, the overview of the most common errors helps to find a remedy quickly and easily.
Lack of alcohol
The emptier the petrol tank on the lawnmower becomes, the more fuel sloshes back and forth in the tank while mowing. If the petrol is running out, air can get into the fuel line again and again. As a result, the engine receives too little fuel for ignition. These missing or improperly running ignition processes are expressed in such a way that the lawn mower stutters and, with an increasing proportion of air bubbles, also dies completely.
- Cause: no constant fuel supply due to air in the fuel line
- Solution: refuel
The air filter
The lawn mower also stutters in the opposite case. If the air filter is not able to reliably supply the necessary combustion air, an excessively high proportion creates a non-ignitable mixture for a short time, which the spark plug cannot cause to explode. The result is misfiring and the well-known stuttering of the engine.
- Cause: Dirty air filter due to dust, dirt and grass particles
- Solution: Remove and clean the filter insert, replace the disposable paper filter (blow out or tap it out for a short time, but due to possible damage to the paper material, which cannot be used indefinitely, replacement is mandatory in the long term)
The fuel filter
Here: Also rusty tank, dirty petrol etc. as causes
If the passage of fuel through the fuel filter is reduced, the carburettor is no longer fully supplied. Here, too, the result is an air-fuel mixture that is temporarily no longer optimally ignitable, which the user can perceive as a clear stuttering.
- Cause: dirty fuel filter
- Solution: Close the fuel tap, open the filter housing and remove, clean or replace the filter and then reinstall it, open the fuel tap and start the engine again
The engine stutters acutely when the filter no longer allows the necessary fuel to pass through. However, the actual cause lies elsewhere, especially with the filter becoming clogged again and again. Either the fuel is already heavily contaminated when refueling, or dirt gets into the tank and fuel line in some other way. In older models with a metal tank, this rusts very quickly if the tank is not completely filled for a longer period of time. The result is rust particles that come loose and close the fuel filter within a very short time.
carburetor problems
Sometimes the supply of air and fuel to the carburetor is perfectly fine. However, this heart of the engine may not be able to reliably produce the required mixture of both components. The result is mixing ratios that repeatedly deviate from the target, which then ignite with a delay or not at all, causing the lawnmower to stutter.
- Cause: Dirty, defective or poorly adjusted carburetor
- Solution: shut off the fuel supply, open the carburettor and clean all components including the float chamber and needle, then check that all parts run smoothly and are fully functional and reassemble, restore fuel supply and restart the engine; Check the carburetor setting and readjust according to the manufacturer’s instructions
The spark plug
If the air filter, fuel supply and carburetor are in good working order, an unreliable spark plug can lead to individual ignitions of the mixture in the cylinder not taking place. The engine sputters and ejects the fuel-air mixture as a light cloud through the exhaust. In order to produce this effect, the spark plug does not necessarily have to fail completely. Even changing the ignition point can be enough to throw the combustion engine out of sync with the smooth and even running of the engine.
- Cause: defective, heavily soiled or worn spark plug.
- Possible solution: pull off the ignition plug, unscrew and check the spark plug with a suitable tool, clean with a soft wire brush; replacement in the event of a defect or heavy wear – screw in the cleaned or new spark plug and replace the ignition cap
Wrong handling
If the lawn mower is technically in good order, another, but by no means the rarest, reason for a stuttering engine is incorrect handling by the user. The lawn mower is regularly laid on its side to clean the blades. If this tipping is done in such a way that the tank gets over the air filter and carburetor, fuel can leak or overflow.
- Cause: Fuel in the air filter, too much fuel in the carburettor
- Solution: Pull the starter cable through several times to suck fuel out of the air filter or carburettor through engine movement
Blocked knives
Finally, blocked blades can also lead to engine stuttering. If you drive over stones or branches while mowing, the blades stop briefly. Due to the direct connection between the cutter bar and the engine, the standstill is transferred to the lawnmower, which reacts with disturbed ignition behavior and stuttering.
- Cause: Driving over foreign bodies that cannot be mowed, possibly blunt blades
- Solution: check the lawn before mowing and remove foreign objects, raise the cutting height; Sharpen or replace blunt knives
