The lawn mower is the hobby gardener’s favorite tool. Because with it, the beloved lawn can be cut back to the desired length in an effortless and reliable manner. Even if the lawn mower is not completely on strike, changes in operation should be carefully observed. Because even if the lawnmower engine smokes, this can indicate deviations from normal operation, which in extreme cases can lead to real damage to the engine.

Smoke from the lawnmower

When the lawnmower smokes, it doesn’t always mean the worst immediately. However, so that the causes do not grow into a real problem, you should still react quickly and localize and eliminate the cause. Since you don’t know why the engine is smoking at first, a “quickly…” is also inappropriate. If there is actually a serious defect, even mowing the last bit of lawn can be enough to ultimately lead to major damage.

White or blue smoke

If the engine emits blue or white smoke during operation, this is usually a sign that operating materials are evaporating. Depending on whether it is oil or petrol, the causes can be very different:

Note: White or light smoke is an indication of evaporating operating materials. Physically correctly described, it is actually vapor, i.e. liquid particles transported in the air. However, the phenomenon is commonly referred to as smoke or fumes, so we will keep this designation in the following.

Spilled supplies

If petrol or oil spills onto the engine block next to the filler opening when the lawn mower is being refuelled, it will later heat up so much when the engine is running that it will vaporize. The result is white or blue smoke that does not rise from the exhaust but from the engine block in general.

  • Cause: Spilled operating materials
  • Remedy: Switch off the engine and let it cool down, wipe the engine block with a dry cloth

Übervolle Tanks

If petrol or oil tanks are filled too much, certain parts of it can leak out of the tank through the ventilation valves, which are usually located in the cover, and produce smoke on the hot engine block. Here, too, it is not the lawn mower’s exhaust that smokes, but the entire engine block in the area of ​​the tank openings.

  • Cause: Leaking petrol or oil
  • Remedy: Switch off the engine and let it cool down, check the tanks and, if necessary, pour off some of the contents, wipe off any spilled substances with a dry cloth

Improper combustion

It is normal for a combustion engine to smoke a little immediately after starting. Optimum combustion also requires a certain engine temperature, which must first be reached. However, if the engine smokes permanently white or blue, there is more fuel available than it can burn in a controlled manner, so that some of it remains in the exhaust gases as droplets and is expelled.

  • Cause: incorrectly adjusted carburetor
  • Remedy: Adjust the carburetor or have it adjusted

Tilted lawn mower

Tilting the lawn mower to clean the blades can result in oil escaping and smoking on the engine. In addition, if the engine is tilted with the spark plug pointing downwards, gasoline can enter the combustion chamber, which then burns as excess fuel after starting, producing large amounts of smoke.

  • Cause: Leaked operating materials due to the mower tipping over
  • Remedy: if leaking onto the engine block, switch off the engine, let it cool down and remove it. No remedy required if there is petrol in the combustion chamber, as there is no risk of permanent smoke development
Note: Of course you have to tilt a lawn mower to clean the blades. However, the manufacturers often specify a tilting direction so that the undesired leakage of operating materials is prevented.

black smoke

Even for laypeople, black smoke can be clearly distinguished from the causes described with light or bluish smoke formation. This is real smoke, i.e. burned particles, mostly soot, in the exhaust gases.

Clogged air filter

A certain ratio of petrol to air is required for optimum fuel combustion. If the air filter can only provide a limited amount of air, the petrol will still be burned, but only in an unclean manner and with a lot of smoke.

  • Causes: dirty air filter
  • Remedy: Remove filter, knock out paper filter and clean with compressed air, blow out foam filter or clean with water and soap solution and then dry completely, alternatively replace the filter

Dirty carburetor

One of the most common causes of dense, black space is dirt in the carburetor. Supplied with either the fuel or the air, it passes from the carburetor into the combustion chamber. The remains of the burnt dirt particles excreted with the exhaust gases are then visible. In addition, the contamination usually impairs the function of the carburetor, so that the amount of fuel and air is no longer correct and unclean combustion increases.

  • Causes: Impurities in the carburetor, mostly as a result of problems with the air or fuel filter
  • Remedy: Drain off the fuel, open the carburetor and clean it with petrol, carburetor spray or a brush, then close it again and restore the fuel supply

Sooty spark plug

If the spark plug is fouled, these particles are emitted in the exhaust gases and appear as black smoke.

  • Causes: Dirt on the spark plug head caused by impurities in the air or gasoline, improper fuel-air mixture, or spark plug failure
  • Remedy: Let the engine cool down, pull off the connector, unscrew the spark plug with a spark plug wrench and clean it, then reinstall it and attach the connector

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