Why is my Lawn Mower Smoking?

Why is my Lawn Mower Smoking?

When you’re using your outdoor equipment, smoke is something you typically don’t want to see; the BBQ or grill being the exception, of course! When it comes to your lawnmower, however, smoke is an alarming symptom to see. In this article, we are going to troubleshoot what may be causing this problem and walk you through the repair process for each.  

Issue # 1: The Carburetor (Black Smoke)

The carburetor brings air and fuel together and mixes them in the perfect ratio for combustion. If the carburetor isn’t working properly, then that ratio could be off. Too little fuel will damage your engine, too much fuel will create a mixture that is too rich. The excess fuel won’t be burned completely, which will result in a carbon buildup that leads to black smoke. You can inspect this part by removing the carburetor, taking it apart, giving it a thorough cleaning, and inspecting it for signs of damage. If necessary, it should be replaced. Be careful not to damage the jets during the cleaning.  

Most engine manufacturers have the carburetor mix fuel and air at a ratio that is ideal for engines running at sea level. If you live at a higher altitude, the thinner air may be affecting the ratio, and a high-altitude kit can be installed. 

Inspecting the carburetor

Issue # 2: The Air Filter (Black Smoke)

The air filter prevents debris like dirt, dust, and grass from being pulled into the carburetor and the engine. If you go too long without cleaning your air filter it will eventually get plugged up and stop delivering air into the engine. As we learned with the carburetor, if there isn’t enough air that means too much fuel, which again leads to black smoke coming out from the exhaust.  

You should inspect the condition of the air filter at least once a month and clean it if necessary. The filter should be replaced at least once a year. It is important that you use the filter specifically for your model of lawnmower, and this ensures a proper fit. An incorrect size will not filter out debris properly.  

Side by side of a clean air filter versus a dirty air filter

Issue #3: The Piston Rings (White Smoke) 

The piston rings form a seal between the piston and cylinder walls. If these become worn or damaged, oil can leak past the rings and into the combustion chamber, which will give off white smoke. To avoid this, make sure that the air and fuel filters are clean. If they’re dirty or missing entirely, you will get dirt in your combustion chamber that will wear away the piston rings and cylinder wall.  

Be sure not to neglect the oil in your lawnmower. Bad oil or low oil won’t lubricate the engine properly, leading to piston ring and cylinder wear. Frequently check your oil to prevent engine wear or seizing. The oil should be changed after approximately 50 hours of use. Old, dirty oil is full of particles that the air or fuel filters weren’t able to trap, and continuing to use this oil will cause wear on the engine and its various parts. Replacing piston rings and cylinders that have become damaged is not a simple repair, as the engine needs to be taken apart to access them. Regular maintenance is much easier to do than a complete repair!  

Piston ring

Regular and preventative maintenance is the best way to ensure your outdoor power equipment runs efficiently and lasts you many years. If you need any replacement parts for your lawnmower, you can find them on ereplacementparts.com by searching for your model number. Be sure to subscribe to our YouTube channel so that you don’t miss any repair content! 


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