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Chainsaw Vapor Lock. Tips from a Professional

Chainsaw engines are prone to get overheated during use. Not only does overheating affect the components’ life, but it also contributes to a vapor lock, which makes it challenging to start the engine. Quite often, the users are unaware of a chainsaw vapor lock and its possible risks; hence I shall discuss this issue in detail in this blog post.

Chainsaw vapor lock:

A chainsaw that is vapor-locked has trouble starting just after a run. The gasoline vapors accumulated in the fuel lines exert back pressure, depriving the engine of sufficient fuel. Opening the fuel tank’s cap often allows the vapors to escape into the environment. To prevent this condition, always ensure you run your engine idle for a few minutes before shutdown, and never operate it at WOT.

I will further explain why a vapor lock develops, how you can fix it, and how you can stop a chainsaw vapor lock. At the end of the article, I will also show why your chainsaw can die when it is hot.

How do I Know if a Chainsaw Engine has a Vapor Lock?

If your chainsaw engine has a vapor lock, it will start perfectly, but as it heats up, it will act as if it’s run out of fuel. Sometimes, it wouldn’t start up after turning the engine off.

Vapor lock is a condition when gasoline vaporizes excessively in the fuel tank and the fuel lines. As a chainsaw heats up, the vapor pressure in the fuel lines increases. This heating effect worsens when the saw is run at wide-open throttle (WOT) or when the carburetor is adjusted to a lean setting.

As the vapor pressure builds up, the carburetor faces difficulty extracting gasoline through the fuel lines due to the backpressure created by the vapors. The engine, as a result, starves from fuel, and hence it may not start again after it has been shut down after a heated operation.

Usually, all fuel tanks have vents to allow the escape of fuel vapors into the atmosphere. Hence the vapor pressure doesn’t escalate too much to trigger a vapor lock. If you experience that your overheated chainsaw doesn’t start up, check your tank vents for any clogging.

Also, in the case of vapor lock, the chainsaw starts just fine when it is cold and runs perfectly too. As it begins to heat up, it might show signs of bogging down and feel like the fuel has run out. If, in this case, you shut the engine off and restart it without checking the fuel tank, it will not start again. This would confirm that your engine has indeed developed a vapor lock.

How do you Fix a Chainsaw Vapor Lock?

One way to fix a vapor lock is to open the fuel tank’s cover and allow the vapors to escape the fuel lines. However, the safest way of fixing this is to allow your chainsaw to cool for some time before starting it again.

Fastest Way:

As discussed earlier, fuel vapors are trapped in the carburetor and fuel lines. These vapors exert an additional back pressure, thus hindering the fuel flow to the engine. The quickest way of removing these vapors is to allow them to escape back into the atmosphere. This can be done by opening your fuel tank’s cover and letting all the vapors escape.

As the vapor pressure falls, the fuel flow will ease down, and the engine will start as a result. This method, however, is certainly not the safest. It can be risky to let highly pressurized fuel vapors escape into the atmosphere as they tend to ignite and start a fire, particularly in a closed environment. Furthermore, if these vapors are hot enough, they may cause burns to your skin.

Safest Way:

The safest way is to ensure these vapors cool down and condense within the fuel lines. To do this, you can stop your engine and let it sit for a while. This may be more time-consuming if you want to start quickly. To speed up the process, you can pour cold water on the carburetor and the engine area. This will further help cool down the vapors and fix the vapor lock.

Useful Tip:

Some users turn the choke on and set their carburetor to a rich setting when they encounter a vapor lock. They do so to enrich the mixture with more fuel, which was restricted due to the vapor lock. I wouldn’t recommend this, as after the vapor lock is fixed, your engine will run a lot richer and may experience difficulty while running.

This can also unnecessarily increase your device’s fuel consumption. Also, avoid adjusting your carburetor to a lean setting, which causes overheating and further aggravates the vapor-locking effect.

How do you Stop a Chainsaw Vapor Lock?

To prevent your chainsaw from vapor locking, avoid running it lean or overheating it. Ensure you always let the engine idle before shutting it off.

Vapor locks can be quite frustrating if you have work to finish. To save yourself from the trouble of fixing them over and over, here are some tips and tricks that can help you prevent chainsaw vapor locks.

1. Avoid Running at WOT:

Running your chainsaw at wide-open throttle (WOT) overheats it excessively. I would never recommend you to run your saw at WOT for more than a short period. The heat generated is enough to boil the gasoline, thus causing a vapor lock. Prolonged operation at WOT can even cause damage to the engine components along with the guide bar and chain.

2. Avoid Running Lean:

Most users like running their newer chainsaws lean, saving them fuel and providing them with higher RPMs to cut through tougher wood. Depending on their adjustment, the L and H screws at the carburetor make the mix either rich or lean. It would be best to understand that lean mixing ratios can cause your chainsaws to overheat and eventually result in a vapor lock.

3. Idle Before Shutdown:

Vapor lock often occurs when you restart a chainsaw that has just been hot after an operation. Before shutting your engine, I recommend letting it idle for a minute or two. Doing this would cause a gradual drop in the engine temperature, and the fuel vapors would also cool down. Hence, when you restart the chainsaw, it won’t get vapor locked.

4. Keep a Check on the Fuel:

Most chainsaw-related issues arise during the transition from winter to summer. Fuel blend during winter is often lighter than in summer; hence, it vaporizes at a comparatively lower temperature. This is often the case when the temperature rises at the onset of spring. Therefore, you should check the fuel and ensure that a summer-blend fuel is used during summer to avoid vapor lock issues.

5. Store it in a Cool Place:

As you sometimes see, never place your chainsaw out in the sun, as this is the easiest way of getting a vapor lock. Even after you’ve paused your work, please place it in the shade away from the sun so it doesn’t get hot. A chainsaw kept in the sun will have a higher chance of developing issues when starting up due to a buildup of fuel vapor pressure in the lines.

6. Keep the Vents Clean:

Perhaps the most important and yet the most ignored trick is to keep the vents of your fuel tank clean and deposit free. These vents are especially created to prevent any vapor buildup in the fuel tank and are likely to get plugged with dust and debris. Use a thin metal wire to keep them fully opened and clean.

Why does my Chainsaw Die When Hot?

If your chainsaw dies when hot, it may be due to a clogged arrestor screen or filters plugged with debris. A restricted carburetor or a vapor lock in the fuel lines could also be the reason behind a chainsaw dying when hot.

There can be multiple causes behind a chainsaw that bogs down when overheated. Some of the major causes are:

1. Clogged Spark Arrestor:

The spark arrestor screen is a meshed wire that catches and diminishes spark at the exhaust port. Due to rich settings, the arrestor screen gets plugged with ash and soot deposits. Hence, the engine’s compression lowers, which may not be enough to keep the chainsaw running.

To fix this problem, the exhaust muffler needs to be disassembled, and the arrestor screen should be cleaned thoroughly with a torch flame till the plugged deposits have been dislodged completely.

2. Blocked Filters:

Whenever you experience that your engine is delivering lesser power than usual, always begin by checking the filters first. The air filter is located underneath its cover at the rear end of the saw, while the fuel filter can be found in the tank bottom at the start of the fuel line that leads to the carburetor. Both these filters should be cleaned and must be free from any debris.

To clean the air filter, use a wire brush and a soap-water solution so that no dust or debris remains. For the fuel filter, insert a thin metal wire into the filter to dislodge any stale fuel remains.

3. Faulty Carburetor:

The carburetor is the main agent where the air and the fuel meet before entering the engine. Usually, 90% of the problems are likely at the carburetor. The carburetor jets need to be kept entirely clean from fuel deposits. Furthermore, you must ensure that its internal components, such as the diaphragm, aren’t worn out.

Apart from that, the carburetor’s adjustment screws need to be properly adjusted so that the chainsaw is tuned to an optimal fuel setting. This would prevent bogging down at high RPMs.

4. Vapor Lock:

If a chainsaw is overheated due to a lean run or higher ambient temperature, it’s prone to getting vapor locked. To fix a vapor lock, keep your tank’s cap open for a while to allow the gasoline vapors to escape from the fuel lines. Alternatively, you can cool down your chainsaw by pouring cold water over the fuel tank while keeping the engine off.

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  1. Raymond Holland says:

    Are there any warning signs that indicate a chainsaw is developing a vapor lock?

    • Allard Vdhooft says:

      Raymond, signs of a chainsaw experiencing a vapor lock include starting fine when cold but struggling to start after getting hot. To prevent this, avoid running lean, let it idle before shutdown, and ensure your fuel tank vents are clean.

  2. Thomas Burton says:

    I never knew chainsaw engines could have vapor lock issues.

    • Allard Vdhooft says:

      Thank you for your comment, Thomas. Yes, vapor lock issues can indeed arise with chainsaw engines, especially after prolonged use. Consider taking preventative measures to avoid this problem in the future.

  3. Alice Harris says:

    Very informative post about vapor locks in chainsaw engines!

    • Allard Vdhooft says:

      Thank you, Alice! I’m glad you found it informative. If you have any more questions about chainsaw vapor locks, feel free to ask!

  4. Mathew Powell says:

    Can a vapor lock cause permanent damage to a chainsaw engine?

    • Allard Vdhooft says:

      Vapor lock can cause damage to a chainsaw engine if not addressed properly. Prevent it by following the tips in the blog post to avoid permanent damage.

  5. Felicia Hart says:

    How long should I let my chainsaw cool down before trying to start it again?

    • Allard Vdhooft says:

      Allow your chainsaw to cool for at least 10-15 minutes before trying to start it again to prevent vapor lock. This will help ensure smooth engine operation.

  6. Christy Oliver says:

    I’ll definitely be more cautious with running my chainsaw at WOT now.

    • Allard Vdhooft says:

      Thank you, Christy! Being cautious while running your chainsaw at WOT is crucial to avoid potential vapor lock issues. Stay safe and keep up the good work!

  7. Dustin Davis says:

    Can a vapor lock affect the performance of a chainsaw while it’s in use?

    • Allard Vdhooft says:

      Vapor lock can indeed affect a chainsaw’s performance while in use. I have detailed the causes and solutions in my blog post. Check it out for more information!

  8. Vernon Weaver says:

    The video links provided are a nice addition to the post.

    • Allard Vdhooft says:

      Thank you, Vernon Weaver! I’m glad you found the video links helpful in understanding chainsaw vapor lock. Your feedback is much appreciated.

  9. Joan Roberts says:

    How often should I check the vents on my chainsaw’s fuel tank?

    • Allard Vdhooft says:

      Hi Joan, it’s recommended to check the vents on your chainsaw’s fuel tank frequently to prevent vapor lock issues. This will ensure your engine runs smoothly.

  10. Billy Morales says:

    Are there any safety precautions to take when fixing a vapor-locked chainsaw?

    • Allard Vdhooft says:

      Hi Billy, to fix a vapor-locked chainsaw, allow it to cool before restarting or open the fuel tank cap to release vapors. To prevent, run idle before shutdown and avoid running lean or at WOT.

  11. Brad Hopkins says:

    Very detailed explanation of why a chainsaw may die when it’s hot.

    • Allard Vdhooft says:

      Thank you for your feedback, Brad. I hope the detailed explanation helped clarify any questions you had about chainsaw vapor lock.

  12. Dave Hughes says:

    I like how the post offers solutions to fixing a vapor-locked chainsaw.

    • Allard Vdhooft says:

      Thank you for your feedback, Dave! I’m glad you found the solutions helpful in fixing a vapor-locked chainsaw. Let me know if you have any more questions.

  13. Debra Simmons says:

    Thank you for providing such thorough information on chainsaw vapor locks.

    • Allard Vdhooft says:

      Thank you, Debra! I’m glad you found the information on chainsaw vapor locks helpful. Let me know if you have any other questions.

  14. Colleen Jimenez says:

    I appreciate the tips on how to prevent chainsaw vapor locks.

    • Allard Vdhooft says:

      Thank you, Colleen! I’m glad you found the tips helpful in preventing chainsaw vapor locks. Feel free to reach out if you have any more questions or need further assistance.

  15. Javier Fuller says:

    What should I do if my chainsaw still won’t start after fixing a vapor lock?

    • Allard Vdhooft says:

      Hi Javier, Try allowing your chainsaw to cool down before starting it again after fixing a vapor lock. It’s a safer way to prevent the issue from reoccurring. Hope this helps!

  16. Timmothy Collins says:

    This post is so helpful, especially for beginners like me.

    • Allard Vdhooft says:

      Thank you for your feedback, Timmothy! I’m glad you found the post helpful. Feel free to reach out if you have any more questions or need further assistance. Happy chainsawing!

  17. Gilbert Alvarez says:

    What type of fuel is recommended to avoid vapor locks in chainsaw engines?

    • Allard Vdhooft says:

      It is recommended to use a summer-blend fuel, avoid running lean, and let the engine idle before shutdown to prevent vapor locks in chainsaw engines.

  18. Terry Graves says:

    This post has given me a better understanding of chainsaw maintenance.

    • Allard Vdhooft says:

      Thank you, Terry! I’m glad the post helped you understand chainsaw maintenance better. Stay tuned for more helpful tips and information.

  19. Timmothy Frazier says:

    Great explanation of what a vapor lock is and how it affects chainsaw engines.

    • Allard Vdhooft says:

      Thanks, Timmothy! I’m glad you found the explanation helpful. Let me know if you have any more questions about chainsaw engines or vapor locks.

  20. Leroy Hansen says:

    Is there a way to prevent vapor locks in older chainsaw models?

    • Allard Vdhooft says:

      To prevent vapor locks in older chainsaws, avoid running at wide-open throttle, running lean, and ensure the engine idles before shutdown. Keep vents clean, use correct fuel blends, and store in a cool place.