Chainsaw Won’t Start When Hot? Here’s What to Do

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Do you own a chainsaw, and it gets hot from time to time and stops working, but you don’t know the reason? If yes, then you are in the perfect place to know the answer.

Chainsaw won’t start when hot is a problem that most chainsaw users face from time to time. If the chainsaw doesn’t start when it is hot, it could be due to a number of reasons like vapor lock, air leakage into the carburetor, worn-out piston rings, and faulty ignition module and spark plug, among others. If any of these things happen, your chainsaw could die suddenly and not start when you’re trying to start cutting again.

In this article, you will get to know about chainsaws being hot, why do chainsaws die when hot, reasons why chainsaw won’t start when hot, how to fix a chainsaw that is hot and not starting, different chainsaw techniques that you must know about, and more. Continue reading to get all the answers that you are looking for.

Why Chainsaw Won’t Start When Hot

Does your chainsaw die down when you’re cutting at full throttle, despite running properly for a certain time? This seems to be a common issue that has mainly been occurring with older chainsaw models. If your gas-powered chainsaw isn’t starting after becoming hot, then there are a few factors involved in this issue. Some of them are the fuel delivery, the engine’s compression, and the ignition system. 

The fuel delivery will deal with the fuel flow from the tank to the engine through the carburetor and the fuel lines. If there is any obstruction in the fuel line inhibiting the flow, it can cause this issue to occur. The spark plug is responsible for providing the ignition to initiate combustion. A faulty spark plug can cause the engine to die down and not start.

There is another reason that does not get spoken about enough – a piston ring failure. Typically, older engines will be more likely to have scored cylinder walls. This can lead to increased wear and tear, which can prevent the engine from producing enough compression, which leads to the saw dying out. Here are some of the other reasons why your chainsaw will not start when hot –

1. Restricted fuel supply

A heated engine will more often than not restrict the flow of fuel to the chainsaw carburetor. This can either be due to a dirty fuel filter or due to damaged fuel lines.

If this happens, the solution will be relatively painless. A dirty fuel filter will require an immediate replacement if you aren’t able to clean the dirt off of it. For clogged fuel lines, you need to replace them with new ones, and you’ll be all set to start your chainsaw.

2. Fuel vapor lock

The most common issue that is causing the chainsaw to run slowly or die down and not start after hot is the vapor lock in the fuel lines. There are many cases in which chainsaws were kept under the sunlight for a prolonged period. When the user started using the chainsaw, they started experiencing this problem. The high temperature can cause excessive vapor buildup in the fuel lines, which prevents the liquid fuel from flowing into the carburetor.

It’ll create a lean mixture, so as a result, the chainsaw might start properly. As soon as you’re revving it up, the higher temperature will further increase the vapor pressure. This will completely limit the fuel supply. It can cause the chainsaw to die out and not start when hot.

To prevent this from occurring, you should ensure that the tank vents are not plugged with debris or dirt. These vents will make sure that the trapped vapors can escape. Moreover, you should open the fuel cap for some time while allowing the pressure to equalize. After that, you should close it and then start the chainsaw again.

3. Plugged carburetor

Your chainsaw’s carburetor is where the air gets mixed with fuel in the appropriate ratio. The air-fuel mix should have a sufficient amount of fuel, or a “rich” fuel mixture to be more precise. The contents of your fuel will be highly likely to cause sticky white deposits inside the chainsaw over time. These deposits could end up plugging the carburetor jets and hence block the fuel supply to the engine. Eventually, the engine will die out when hot, as it won’t receive adequate fuel to produce the required power. 

You need to invest in a carburetor repair kit. For cleaning the carburetor, you will first have to take it off by removing the air filter. A carburetor cleaner spray is a handy product for dislodging the sticky deposits in the jets and making the carb up and running again. You should ensure that there are no fuel residues present after you have finished cleaning the carburetor.

4. Defective ignition

The spark plug electrode will initiate combustion by providing a spark in the engine. Check the electrode for any potential signs of wear and tear. Check if there is any black carbon buildup deposited on the electrode. This building will likely occur after prolonged use. It will affect spark quality, especially at higher temperatures.

You will have to replace the spark plug if the electrode starts appearing worn out. Another good way of testing the spark plug will be to add starter fluid from the choke valve. Say that the engine doesn’t start with the fluid, or it starts and stalls, the problem will lie in the ignition and needs to be fixed.

5. Inadequate compression

You should remember that the air-fuel mixture must be compressed to a suitable temperature for producing enough power during the power stroke. There are instances of chainsaws that use a single-piston ring in the engine. Even the fuel delivery and ignition system might be operating perfectly.

However, it might be that the engine’s piston ring has worn out to the extent that the compression at high temperatures is giving a reading of 0 psi. Usually, the piston ring will prevent the gases from escaping into the crankcase while also maintaining pressure during the compression stroke. Here, the piston’s wear rate will increase at a high temperature due to thermal expansion. This is why high-temperature compression will be almost zero.

It is advised that you should perform a compression test of the chainsaw before you start it when it is cold, and after you’ve shut it down because of heat. The compression tester gauge will be relatively cheap and could be bought online or from a hardware store nearby.

You should connect the tester to the spark plug socket before pulling the cord in each of the two cases. Then, check if there is any pressure difference between when the engine is hot and when the engine is cold. If there is any discrepancy in pressure, it will mean that the fault lies in the piston and cylinder. Depending on the damage, you might have to buy a new chainsaw.

Why Does the Chainsaw Start When Cold but Not Restart When Hot

If your chainsaw doesn’t start when it is hot, you need to check the fuel tank to see if there is a vapor line in the fuel lines. Moreover, check the carburetor and inspect for leakage or fuel blockage. Fuel tanks could get vapor locked because of some ingredients present in the gas. You should always keep a check on the fuel tank’s vents and ensure that no debris gets accumulated. The vents will prevent vapor lock formation.

You must check the carburetor’s jets and ensure that you keep them clean and free of any debris. You should avoid running the engine on a lean fuel setting, as it overheats specific engine components and makes them prone to failure. It includes different seals and gaskets, which are likely to be damaged because of high-temperature exposure. This is key to preventing piston failure. Moreover, some spark plugs won’t fire if they become too hot, which is why your chainsaw won’t start when hot.

Air leakage into the carburetor will become imminent if the carburetor engine connection ends up becoming loose. There are instances when damaged O-rings at the connection might cause the air to leak into the carburetor. This will create a lean air-fuel mixture, which overheats the engine further. The heat will wear out the rings, so the mixture will be much leaner. Eventually, the engine will die out as the air-fuel mixture will be too lean to sustain combustion.

Moreover, it can also be that the ignition module struggles to operate at higher temperatures. Besides, it can be that the spark plug has worn out to an extent that it won’t produce a spark until it cools down. Vapor lock is one of the most common reasons why the engine won’t start when hot. The heat will cause the fuel to evaporate, raising the vapor pressure that inhibits the further flow of the fuel to the carburetor

Running the engine lean over a long period will likely cause piston failure. The heat can cause thermal expansion, which makes it likely to alter cylinder walls and damage the piston rings or gaskets. This will eventually lower the engine’s compression, and it will not start as a result.

My chainsaw is smoking and overheating

How to Fix a Chainsaw that Won’t Stay Running

A rich fuel mixture will likely stall your chainsaw. The presence of air will ensure that the chainsaw can be sustained, and a sufficient firing temperature could be achieved such that torque delivery will be adequate to keep, the engine running. 

Once the air filter gets plugged in, the mixture will most likely become rich. Hence, you need to inspect the filers and ensure that they aren’t plugged with any dirt or debris. Make sure that the carburetor’s jets are deposit-free and promote the unrestricted flow of air and fuel. 

Moreover, the carburetor adjustment screws have to be tuned in case it stalls. The low-speed adjustment screw will control the fuel flow to the carburetor if the throttle isn’t pressed. In case the screw is too loose, the mixture will become too rich. Hence, you will need to tighten the screw by a certain amount and check if the mixture is lean enough that it keeps the engine running.

Why Do Chainsaws Get Hot

In case the guide bar’s oil runs out, the friction because of metal-to-metal contact will drastically increase. This will end up overheating the guide bar and chain quickly. If the situation is not resolved, it will be highly likely to damage the chainsaw or even start a fire.

Further, the chainsaw’s RPMs will increase considerably if the carburetor is tuned to operate at a lean fuel mix. This will also overheat the chainsaw. There are many instances where experienced users run their chainsaws at Wide Open Throttle (WOT) once it gets stuck while cutting wood. This ends up destroying the chainsaw eventually. You shouldn’t run the engine at WOT as it can damage the engine components considering the lean fuel mixture that it is operating at.

Lastly, it is advised that you should always mix the engine oil and fuel in the ratio that is prescribed by the owner’s manual. 

professional logger trying to start a chainsaw

Chainsaw Cooling Techniques that you Need to Know About

There are numerous factors that contribute to a heated chainsaw. This leads to the chainsaw bogging down and not restarting.  You can avoid them if you know different chainsaw cooling techniques.

  • You should always keep a check on the fuel tank so that you can ensure it has ample fuel
  • When going for a refuel, you shouldn’t add fuel to a hot engine 
  • Tighten the nuts and bolts of the chainsaw regularly that end up loosening with usage 
  • You shouldn’t leave the battery-powered chainsaw out in the open and exposed to sunlight when it isn’t being used
  • Sharpen the chainsaw chain blades from time to time using an electric file
  • Right after use, you need to look for any debris and clean the chainsaw if required 
  • You should only store the chainsaw after cleaning it


Should I get a new chainsaw if my chainsaw doesn’t start after getting hot?

No, you don’t necessarily need to purchase a new chainsaw if it doesn’t start after getting hot. You need to go through the reasons and the solutions mentioned above, and you can get your chainsaw functioning again.

Should I run my chainsaw at full throttle?

Generally, two-stroke chainsaw engines are built in a way to conveniently run at full throttle without resulting in an engine breakdown. Therefore, running the chainsaw at any throttle speed less than the full throttle isn’t advised.

Can low oil result in overheating?

Overheating is largely noticed when the coolant is low, but low oil can also cause the chainsaw engine to overheat. It can occur even if the coolant level is fine. In case there is too little oil in the engine, it’ll continue heating up since it hasn’t had an opportunity to cool.

Why do fuel lines and carburetor get clogged even when I clean them regularly?

This usually happens when you’re using old fuel or letting the fuel stay in the tank even if the chainsaw isn’t being used. You should avoid leaving fuel in the chainsaw when you don’t need it. Moreover, you should always add fresh fuel and a suitable fuel stabilizer to the fuel to retain it for a long time.

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Hi, I'm Mike - but my friends call me Backyard Mike. I'm the founder of this website, and I'm addicted to outdoor power tools. I love to work with wood and share my knowledge here on this website with you. You can find more about me here.