Why Does My Lawn Mower Blow Out Black Smoke & Now Doesn’t Start?

Users of lawn mowers often face the problem of black smoke coming out of their mowers which not only causes pollution in their surroundings but also restricts their ability to trim their grass/lawn according to the planned schedule. While some people say that after giving out black smoke it keeps on working properly, others suggest that their mowers stop working after throwing out rings of black smoke for a long period of time.

There are basically two reasons for this behavior of the lawn mower, either the gasoline to the air ratio is a lot i.e. the mower consumes much more gasoline as compared to the air, during mowing operations or an indication that oil has reached inside the cylinder and the mower is making efforts to burn the oil along with the fuel present inside the cylinder.

How to fix black smoke on lawn mower

1. Check whether the oil level is sufficient or not and if the oil looks fresh or not. Immediately get the oil changed if it looks too black or hasn’t been changed in a month or so.
2. If your filter has become quite old then you should definitely buy a new one (it is a paper filter but if it is a foam filter then it can be cleaned and sprayed with a light layer of engine before installing it) and always remember that cleaning up the air filter with soap and water, every week, is extremely essential to let the mower function appropriately.
3. Cleaning or changing the spark plug can also make a huge difference. Many lawn mowers blow out black smoke because of a nonfunctional spark plug so what you need to do is pull off the spark plug boot, then remove the plug with a socket wrench and have a good look at the terminals. If you find the terminals to be stacked up in thick deposits then remove the deposits with sandpaper. But in case the terminals look oily to you then you probably have a worn oil seal thus your mower won’t function fully until the seal is repaired.
4. It is very important that all the inner functions of the mower are performing properly to ensure that the black smoke doesn’t transmit from the mower’s engine ever which is why adjusting the carburetor every now and then should be your number one priority if you own a mower. Usually, lawn mowers have two screws adjusted on the outer side of the unit- one is typically used for adjusting the idle while the other one is responsible for regulating the fuel mixture i.e. keeping a balance between the fuel and air ration entering the mower. Extreme opening of the low-speed crew (mostly marked as “L” on mowers) causes the engine to produce black smoke which is why what you need to do is after you’re done locating the adjustment screws (mostly located under the air filter), create a thinner fuel mixture by using a screwdriver to shift the low-speed screws from ¼ to ½ turn clockwise. This will enable a balanced fuel mixture hence more efficient fuel-burning.
5. To remove the grass from the deck and engine of the mower, use water to do so once the engine has cooled off.