Chainsaw Smoking & Overheating Causes & Fixes

Is your chainsaw smoking?

Well, don’t worry because, in this post, I’ll be revealing why your chainsaw is overhearing and how to fix it.

So let’s get straight into this post!

What is causing my chainsaw to overheat and how do I fix it?

Chainsaw is clogged

Chainsaws generate a considerable amount of heat during operation. Air ventilating in and around the saw during operation allows the heat to escape. 

Once the saw becomes clogged up with oil residue and sawdust, the heat cannot escape any longer and the saw will start to run hot.

If the heat cannot radiate into the air, it will continuously heat the oily gunk that is clogging up your chainsaw. 

If your chainsaw gets completely clogged up, and the sawdust/oil build-up gets hot enough, it will start smoking. This is a pre-cursor to a fire starting and should be viewed as critical. 

You need to switch the saw off immediately and let and cool down. Thereafter you need to clean the saw. This may require some disassembly and removal of the outer covers. 

You can use mild degreasing fluid and brushes to remove all the buildup of oil and sawdust. Your objective is to ensure that air can move freely over all metallic surfaces of the saw, in particular, the engine and cylinder housing. 

Not enough oil

Another reason for smoking could be that the chain bar is overheating. During operation, the chain runs across the bar with the resulting friction generating heat in the chain and bar. 

Your chainsaw has been designed to lubricate the chain during operation. The oil finds itself between the chain and bar, reducing friction and absorbing heat. 

Your chain and bar will overheat if it’s not getting enough oil during operation. The problem could be that your oil reservoir has run dry, and you simply need to add oil. 

The oil reservoir has a mesh filter inside to prevent particles from entering into the lubricating system. It could be that the filter is clogged and needs cleaning.  

Your problem also could be that the lubricating holes on the bar have become clogged. This will also require cleaning. You will need to remove the bar, and thoroughly clean the ports on the bar and also on the chainsaw where oil is fed into the bar. 

A simple test to see if the bar and chain are getting enough oil is to run the chainsaw at full speed, keeping the tip of the bar a few inches away from a light-colored surface. 

If you see oil spatter accumulating on the surface, it means that your chain is lubricated and throwing off oil as it should. You can run this test for 30 to 45 seconds. If there is no oil visible after that amount of time, your need to fix the problem before working with the saw. 

Chainsaw won’t cut even after sharpening
Why is my chainsaw hard to pull?
Why does my chainsaw blade get dull so fast?

Chain tension too tight

You may have tightened the chain too much, causing friction. Three main factors influence the amount of friction. First is how smooth the surfaces are. The second is the speed at which the surfaces interact. The third is the amount of pressure between the surfaces. 

The tighter the chain, the more pressure there is between the chain and the bar. This pressure creates excess friction which leads to excess heat, which in turn causes the oil on the chain and bar to smoke. This is an indication that the oil is close to combustion. 

The problem can be easily remedied by correcting the tension on the chain. Always be sure to follow the manufacturer’s instructions on how tight the chain should be set.

Old fuel in the tank

If your chainsaw is not overheating but is still smoking, the problem could be with the fuel. Gas chainsaws burn fuel to operate. Incomplete combustion causes smoke. 

Old fuel or even fuel that has too much lubricating oil mixed into it, will not burn cleanly during operation. Incomplete combustion presents as light or dark smoke coming out of the exhaust. 

Drain off the fuel, and recharge the tank with clean fuel that has the correct ratio of oil mixed into the fuel.

Keep in mind, that chainsaws use two distinct types of oil. The one type of oil, usually thick and dark, is used to lubricate the chain during the operation. This should not be mixed into the fuel.

The other type, usually colored light red or green, is mixed into the fuel and lubricates the engine during operation. If you mix these two types of oil, it could cause the engine to smoke, or damage the chain. This oil should not be used as chain lubricating oil. 

My recommendation is that you keep a can of gas and oil mix specifically for your chainsaw and that you mix the oil and gas in the can before filling the saw’s gas tank. 

Clogged air filter

Many operators state that a clogged air filter cannot cause the chainsaw to smoke. I disagree with that. If the air filter is completely clogged, the machine won’t start. But, if the air filter is heavily clogged, the machine may still run.

During the intake stroke, the piston sucks in air and fuel. A partially clogged air filter will allow enough air for the machine to run. The intake stroke, unable to get enough air, will make up some of the intake volumes with fuel. 

Combustion will be incomplete because of too much fuel with too little oxygen. Incomplete combustion results in high carbon residue in the exhaust gas, which presents as smoke coming off the exhaust.

Cleaning the air filter should alleviate this problem.

The chain is not sharp enough

When the chain is not sharp enough, the operator will try to force a cut by pushing down harder. The extra friction resulting from this could cause the chain and bar to overheat which in turn will cause smoke. 

Make sure you always work with a sharp chain. 

What happens when a chainsaw overheats?

Two separate components could be the cause of overheating.

The first is the engine. This will happen when the machine is clogged up with dirt and airflow is too obstructed to cool the engine. 

This could result in the chainsaw bursting in flames or cause the metal inside to deform or melt. Both are serious situations that can destroy your machine.

The second source of overheating is from the chain and blade. This could cause flames. The main danger once again is damage to metal surfaces. You could lose both the chain and blade to damage. 

Should a chainsaw blade get hot?

The chainsaw blade should get hot. But not too hot. 

Metal friction is high at both very low temperatures and very high temperatures. 

In the middle, there is an optimal sweet-spot where friction is at its lowest. Make sure the tension is right and that lubrication is adequate. Your blade will heat up during operation, but not so much that it causes damage to the chain or blade. 

One last thing, chainsaws don’t do well when cutting dry wood. The sap in wet wood helps to keep the blade cool. Dry wood has no sap and can cause the blade to overheat. 

Conclusion

So that’s why your chainsaw is smoking and how to fix it.

Hope you found what you were looking for in this guide.

Happy sawing!

– Adam