Why does your chainsaw keep smoking? Depending on where the smoke is coming from will tell you a lot about why it is smoking.
A STIHL chainsaw is smoking due to increased friction between the bar and chain, too much oil in the fuel mixture, water in the fuel system, or a plugged air filter.
STIHL Chainsaw is Smoking:
- Dull or incorrectly sharpened chain
- Chain is too tight
- Empty tank of bar and chain oil
- Wrong type of bar and chain oil
- Clogged oiler
- Plugged air filter
- Too much oil in the fuel mixture
- Water in the fuel mixture
Take caution when troubleshooting and repairing your chainsaw. Shut off the chainsaw, wait for the engine to cool, and remove the spark plug boot.
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Follow all safety instructions provided in your equipment operator’s manual before diagnosing, repairing, or operating. Consult a professional if you don’t have the skills, or knowledge or are not in the condition to perform the repair safely.
STIHL Chainsaw is Smoking from the Bar & Chain
When your STIHL chainsaw smokes when cutting, you need to look for items that can cause increased friction between the bar and chain.
This may be due to a dull chain, poor lubrication, or a chain that won’t move freely around the bar.
Dull Chain or Incorrectly Sharpened Chain
A dull chain will cause your chainsaw to smoke and not cut wood efficiently. This is because a dull chain or a chain that isn’t sharpened correctly will cause you to have to apply more pressure to cut wood.
This pressure causes metal-on-metal friction creating heat and smoke.
Look for these signs indicating the chain is dull:
- Needing to apply increased pressure on the bar to make a cut.
- Fine sawdust is created when making a cut.
- Chips or damage to the chain.
- Worn teeth and rakers.
You can sharpen the chains yourself. If you don’t have experience sharpening chains, I highly recommend having a professional sharpen them for you. A chain that isn’t sharpened right can be a serious safety hazard.
Lack of Bar & Chain Oil
Friction will build when your chainsaw isn’t getting enough oil to the bar and chain. This could be due to running out of oil in the tank or having a clogged oiler.
Fill the bar and chain oil tank if it is low on oil or empty.
To check for sufficient oil on the bar, run your chainsaw at about 1/2-3/4 throttle. What you are looking for is a line of oil coming off the bar while holding it less than a foot off the ground.
If you aren’t getting good lubrication, make sure the bar is in good condition and the oil channel isn’t blocked. Replace a worn or damaged guide bar and clean the oil channel if needed.
It is good to get into the habit of refilling the bar and chain oil every time you fill your STIHL with fuel. However, if the oil you are running in the saw is too thin, you may go through oil at a faster rate and have to check and refill it more often.
Wrong Type of Bar and Chain Oil for a STIHL Chainsaw
Using a bar and chain oil that is too thin may cause bar and chain damage and increased friction causing smoke to come from the bar. An oil that is too thin may not stick to the bar and chain and instead get slung off of it.
Make sure you are using a premium bar and chain oil like these oils from STIHL:
Chain is Too Tight
The chain will loosen as you use it so you’ll need to check it regularly and tighten it. However, if you tighten the chain too much, it will not move freely around the bar and increased friction will result in smoke.
Adjust the chain tension on a STIHL chainsaw:
- Remove the spark plug wire.
- Unlock the chain brake.
- Loosen the bar retaining nuts that hold on the cover over the clutch and chain brake.
- Hold the nose of the bar up.
- Turn the tensioning screw counter-clockwise to loosen the chain and clockwise to tighten the chain.
- Once you achieve the correct tension, tighten the bar retaining nuts while continuing to hold the bar nose up.
You want the chain to sit securely around the bar, but still able to move easily. You don’t want it too loose that it hangs from the guide bar.
STIHL Chainsaw Smoking from the Engine
When your STIHL chainsaw smokes while running, you will need to look at airflow issues including a plugged air filter or a problem with the fuel mixture.
Plugged Air Filter
Operating a chainsaw is a dirty job. Sawdust and small wood chips are tossed into the air.
An air filter is used on your chainsaw to ensure the engine receives clean air. The filter keeps dirt and sawdust from entering the air intake and wearing on the engine.
If you use your chainsaw sparingly, replace your air filter annually and check it before each use. If you use the saw regularly, check the filter frequently and replace it when it becomes very dirty or damaged.
If you don’t regularly check and clean the filter to ensure it is in good condition, the buildup of dirt and sawdust can clog the filter and not allow sufficient air to pass through the filter.
The fuel mixture will run rich and smoke. The engine may eventually overheat and shut down due to a lack of air.
Too Much Oil in the Fuel Mixture
Oil added to the fuel for a STIHL chainsaw adds the lubrication the engine needs to keep running. STIHL chainsaws require gas and oil mixed at a ratio of 50:1. Using more oil than this can cause the engine to begin smoking.
Once you realize the smoke is coming from the wrong fuel mixture, remove the fuel and fill it with fresh fuel with the correct gas-to-oil mix.
This won’t normally cause long-term damage. However, running fuel with too much oil may cause running problems due to an increased buildup of carbon in the exhaust system.
Refer to this article for more information on choosing the right fuel for your STIHL chainsaw.
Water in the Fuel System
Water in the fuel mix can cause white exhaust smoke. Water is corrosive to the fuel system and engine.
You may be looking for a way to remove water from the fuel, but you should empty the fuel tank and refill it with fresh gasoline and 2-cycle engine oil mix.
Trying to save a little money to remove water isn’t worth the potential damage requiring a large repair bill or chainsaw replacement.
Add in a fuel additive like Sea Foam Motor Treatment or STA-BIL to help remove moisture and clean the fuel system. Start the saw and allow it to run to get the treated fuel through the system.
Still Having Problems with Your STIHL Chainsaw?
Check out my handy guide Common STIHL Chainsaw Problems for handy charts listing problems and solutions to many common problems chainsaw owners encounter.
This is a great guide to keep bookmarked. It covers problems with a chainsaw not starting, bogging down, or dying. You can also find information on a chain not turning, the engine only running with the choke on, and more.
In addition, you will find links to more detailed information on each issue.