Chain Saw: Blows Black Smoke From Exhaust

Your chainsaw’s carburetor is responsible for ensuring the correct mix of fuel and air enters the engine. This allows the chainsaw to operate normally. If your carburetor is not adjusted correctly, it can cause too much fuel to enter the engine; this is referred to as an engine that is running rich. When the carburetor causes the engine to run rich, more fuel enters the cylinder than can be completely burned during combustion. This unburned fuel produces exhaust that is carbon-heavy, and it can exit the muffler as black smoke. If your carburetor is dirty or clogged, you can clean it and rebuild it by picking up a new carb kit. However, if it is damaged, shows sign of internal corrosion, or won’t come clean, it is usually easier to simply purchase a replacement carburetor.

The air filter in your chainsaw prevents debris from entering the engine. Over time this debris can build up and develop a clog. A dirty or clogged air filter can reduce the amount of air getting to the carburetor. While this is happening, the carburetor still adds the same amount of fuel to the engine, which will cause it to run rich. An engine that is running rich is the primary cause for black smoke being emitted from your chainsaw’s exhaust. The air filter should be cleaned regularly as a part of normal maintenance, and this should prevent your engine emitting black smoke from the exhaust port.