Skip to Content

Starting a Chainsaw without a Primer Bulb. Tips from a Pro

If your chainsaw doesn’t start after several pulls and the primer bulb appears damaged, you must install a new bulb before the saw can be created. But what if there was a way to bypass the bulb entirely? This blog will explain starting a chainsaw without engaging the primer bulb.

We are starting a chainsaw without a primer bulb.

A primer bulb aids in the cold starting of your engine. If it gets damaged, it can be bypassed simply by blocking the line that connects it to the carburetor. To start your chainsaw with a primer bulb, inject some starter fluid or gasoline through the air filter into the carburetor. Or you can pour it directly into the engine through the spark plug hole. After adding, pull the cord and check if it starts.

The following article gives a detailed explanation of how to start a chainsaw without a primer bulb. I will show how to bypass it and prime a chainsaw with no primer.


Do all Chainsaws have Primer Bulbs?

Usually, low-end chainsaws with smaller engines have primer bulbs installed to aid the cold-starting of the machine. Saws with motors more significant than 40 or 50cc do not have this feature.

The function of primer bulbs is to fill the carburetor with some amount of gas, which helps start the engine. Primer bulbs create a suction when they are pressed. The vacuum draws fuel from the tank and fills the carburetor with it.

When the cord is pulled, this fuel is delivered to the engine, so combustion becomes sustainable. The engine starts as a result.

Another essential function of primer bulbs is purging off the air trapped in the fuel line that connects the fuel tank with the carburetor. The air gets sucked out from the line and back into the fuel tank by pressing the bulb. Hence, the fuel flow to the carburetor gets easier.

Due to this reason, primer bulbs are also called purge bulbs.

In my 20 years of gardening, I’ve noticed that the most common mistake people make when starting a chainsaw without a primer bulb is not properly priming the carburetor manually. This often leads to difficulty in starting the chainsaw. It’s a simple step that can make a significant difference.

Why Chainsaws Larger Than 40cc Don’t Need Primer Bulbs

Engines larger than 40cc create enough compression in their piston cylinders that they do not need to be supplied with an additional fuel charge. Hence, more extensive and high-end saws would require no primer bulbs.

Primer bulbs were introduced for saws that were more suited for domestic use but were not used for longer intervals. Hence, a primer and a choke feature were needed to aid in starting such machines. This helped start engines when temperatures were cold, and the saws weren’t as thoroughly maintained either.

Is it Safe to Run a Chainsaw without a Primer Bulb?

Chainsaws with primer bulbs, especially those with a 35cc or more significant engine, can be run without them. The goal is to supply the machine with some gasoline so that the engine delivers enough power to start the chainsaw.

Primer bulbs are necessary for some engines, as without them, the engine doesn’t produce enough power to start the chainsaw. However, manual priming may help you create a chainsaw if the primer bulb isn’t working in these engines.

– Safety Measures When Running a Chainsaw without a Primer Bulb

To manually prime your chainsaw, you must squirt some fuel or a carb cleaner liquid into the carburetor through the air filter. This additional fuel may help start your engine without a primer. Sometimes, you can add fuel to the engine via the spark plug hole.

These methods ensure the engine receives enough fuel to deliver the requisite power. When done manually, it may become a hassle as you would need to unscrew some parts every time while starting the chainsaw.

Hence, if your device uses a primer bulb that has gone faulty, the best course of action is to replace it with a new one.

So, can you start a chainsaw without primer? Yes, but if your chainsaw is 35cc or more extensive, you might need a primer for a smoother start.

How do you Bypass a Primer Bulb?

Bypassing a primer bulb is simple. Just disconnect the carb line and plug it with a ball bearing to seal it entirely. Then, connect it back to the carb. Ensure that any possible air leakage spots are dealt with appropriately.

Bypassing a primer bulb may seem like an option when you have work to do and can’t find a replacement bulb. Nevertheless, you can still start your chainsaw without a bulb, but if you intend to use a chainsaw for the long term, I recommend installing a new primer bulb instead, as it would ease the starting procedure and be more convenient.

Still, bypassing a primer bulb on a chainsaw is relatively easy.

Bypassing the Bulb: Checking the Primer Bulb

Expose the lines: Unscrew the casing on the chainsaw to reveal the fuel lines that connect to the bulb. Check the primer bulb before you start this process.

  • Expose the lines: Unscrew the casing on the chainsaw to reveal the fuel lines that connect to the bulb.
  • Seal the carb line: The only thing that you need to do is to disconnect the hose linked to the carburetor. Insert a small ball bearing or any other object to seal the line to the carburetor perfectly.
  • Reconnect: Once sealed, connect the line to the carburetor back.

Regular maintenance ensures a chainsaw starts smoothly without a primer bulb. Clean the air filter regularly, check the spark plug, and ensure the fuel mix is correct. Also, properly storing the chainsaw when unused can prevent many issues.

With the line removed, your bulb has been bypassed, and fuel flows directly from the tank to the carburetor. If your chainsaw has a larger engine, do not worry; this process is still applicable.

My Opinion:

Although you have successfully bypassed your primer bulb, now you need to make more effort to start your engine. I recommend that you turn the choke lever to the maximum setting, as this would supply additional fuel to the engine. Plus, readjusting your L and H screws would further help start the machine despite the primer being out of the way.

Some users have found that shaking their chainsaw’s fuel tank builds pressure and fills the carburetor with fuel. This may also aid in starting your chainsaw after the bulb is bypassed. Please note that you would only need the primer to start the engine. Once it’s created, it wouldn’t need the primer anyway.

Remember to pull the starter rope several times to start the engine. This is because the primer bulb draws fuel into the carburetor, making it easier to start the engine. Without the primer bulb, you might need to pull the starter rope a few more times than usual. If your chainsaw has a manual choke, use it to enrich the fuel mixture in the carburetor. This should help in starting the engine.

How do you prime a saw with no primer?

To manually prime a chainsaw, you need to inject some starter fluid into the engine through the air filter. In some cases, it may be added via the spark plug hole.

Equipment Needed:

You need starter fluid and a flathead screwdriver for this procedure, and you are good to go. If a starter fluid is unavailable, make sure you use gasoline mixed with engine oil in 50:1 parts instead.

Things to Consider:

Please keep in mind the following factors before you proceed:

  • Priming time: Depending on your skill level, priming the saw engine without a primer bulb could take 5 to 20 minutes. If you’ve previously performed chainsaw repairs, it shouldn’t take more than 5 minutes.
  • Starter fluid: A starter fluid is required for this kind of priming. The fluid is a mixture of chemicals that act as fuel and aid in starting the engine when it fails to prime.
  • Caution: Use the starter fluid cautiously and avoid spraying too much, which may cause blockage and disrupt the carburetor’s airflow.

● Step 1. Initial Checks:

Preparing the chainsaw for the task is usually preferable before starting the engine. This stage ensures that all fuel lines and carburetor connections are correctly linked. Furthermore, the spark plug wire must be connected, and the spark plug must be in good condition. Check your gasoline tank to see if any fuel needs to be added.

You must now discover and investigate the problem with the priming bulb. It lies close to your carburetor/air filter assembly. It may be located beneath the carburetor in some models. The bulb is usually red or black.

Safety should always be your priority when starting a chainsaw without a primer bulb. Ensure the chainsaw is on a flat surface, the chain brake is engaged, and you have a firm grip on the handle before attempting to start it. These precautions can prevent accidents and ensure a smooth start

Examine your primer bulb to check whether it is cracked or torn. If anything appears to be broken, that is why it does not work. If everything seems in order, press it three times to allow fuel to enter the carburetor and begin combustion.

– To start the engine, pull the cord:

This is an optional step that can be conducted to determine whether the engine starts with a bad bulb or not. After pressing the primer bulb three times, push the choke lever to the maximum position. Pull the cable at least three times to see if the engine starts.

● Step 2. Locate and Remove the Air Filter:

If your engine does not start after completing the above instructions, you should consider manually priming it with starter fluid. But first, we must remove the air filter from which the fluid must be sprayed. I suggest photographing the air filter assembly to assist you in keeping track of individual parts and know where to put them.

– Identify the air filter:

Finding the air filter is quite simple, as it is located on the side and can be easily removed.

– Remove the air filter:

Take the air filter out of the housing. Ensure that the filter assembly is wholly separated from the saw. Remove any nuts, screws, or retention pins connected to the chainsaw.

● Step 3. Spray the Starter Fluid:

Now, you should spray the starting fluid into the air inlet. The air cleaner was linked to the engine at this location. Squeeze some starting fluid into the hole. Avoid spraying too much liquid, which could clog the jets and cause further issues.

Please note that you can pour the starter fluid or gasoline into the cylinder head directly as an alternative. This is done from where the spark plug is present. To do this, first, remove the spark plug boot. Then, drag the spark plug using a correctly sized wrench/socket wrench. Once the pin is removed, add some starter fluid through the hole.

● Step 4. Reconnect the Air Filter Assembly:

We’re ready to start the engine now that fluid is added, but first, the air filter housing and filter must be reconnected to the engine. You should carefully place it back into the housing, fastening it as needed. You must complete this step as soon as possible. Otherwise, the starter fluid containing some fuel may evaporate, and you may need to add it again.

● Step 5. Start the Saw:

After you’ve reassembled the filter and its housing, it’s time to start the chainsaw’s engine as usual. Pull the cable while the choke is set to the maximum setting. It might not start right away, so give it a few attempts.

If the fluid has not yet evaporated, it should start immediately. If it does not start, you may need to add the starter fluid again. If it starts following the fluid spray, you have effectively primed the engine without using the priming bulb.

Leave a comment

We try to answer each comment, but please read our comment rules first here. Use an existing and correct email address as you will receive an verification email. Your email address will not be published. All fields are required.

  1. Chad Perez says:

    What happens if you bypass the primer bulb incorrectly?

    • Allard Vdhooft says:

      You can block the line connecting the primer bulb to the carburetor to bypass it. Add starter fluid through the air filter or spark plug hole to start the chainsaw without engaging the primer bulb.

  2. Johnny Duncan says:

    This is a handy hack for chainsaw owners

    • Allard Vdhooft says:

      Thanks for the feedback, Johnny. Bypassing a primer bulb can be a helpful solution in some cases. Happy chainsawing!

  3. Ernest Ward says:

    Are there any risks involved in bypassing the primer bulb?

    • Allard Vdhooft says:

      You can start a chainsaw without a primer bulb by manually priming it with starter fluid or gasoline. This option is available if your saw has a larger engine and doesn’t need a primer bulb for starting.

  4. Julia Gonzales says:

    Is it safe to manually prime a chainsaw?

    • Allard Vdhooft says:

      Yes, it is safe to manually prime a chainsaw if the primer bulb is damaged. You can bypass it by adding fuel directly into the carburetor. I hope this helps!

  5. Rosemary Romero says:

    The safety tips provided are crucial for anyone attempting this

  6. Stacey Watson says:

    Very informative and detailed explanation

    • Allard Vdhooft says:

      Thank you for the feedback, Stacey. I’m glad you found the explanation informative and detailed, which is the goal of my blog posts. Thank you for reading!

  7. Tracey Carr says:

    I never knew you could start a chainsaw this way

    • Allard Vdhooft says:

      Starting a chainsaw without the primer bulb can be done by bypassing it and priming the engine manually. It may require more effort, but it is possible for a smoother start.

  8. Heather Mendoza says:

    This method seems like a quick fix in emergencies

    • Allard Vdhooft says:

      Thank you for your feedback, Heather. Bypassing the primer bulb can be a quick fix in emergencies, but it’s best to install a new bulb for smoother starting in the long run.

  9. Eleanor Jenkins says:

    What tools are needed to bypass a primer bulb?

    • Allard Vdhooft says:

      To bypass a primer bulb, simply block the carb line with a ball bearing. Then, squirt starter fluid into the carburetor via the air filter to start your chainsaw without the bulb.

  10. Sue Porter says:

    Thank you for sharing this useful information

  11. Wendy Byrd says:

    Can you do this with all types of chainsaws?

    • Allard Vdhooft says:

      Yes, you can start any chainsaw without a primer bulb, regardless of the type. Just follow the steps outlined in the blog post.

  12. Alvin Carroll says:

    What are the potential benefits of bypassing a primer bulb?

    • Allard Vdhooft says:

      Typically, bypassing a primer bulb involves disconnecting the carb line and sealing it with a ball bearing. It can be done in a pinch, but I recommend replacing the bulb for long-term convenience.

  13. Gene Beck says:

    I like how the article breaks down each step clearly

    • Allard Vdhooft says:

      Thank you, Gene! I’m glad you found the breakdown helpful. Starting a chainsaw without a primer bulb can be tricky, so I hope this guide makes it easier for you.

  14. Beth Romero says:

    I will definitely try this if my primer bulb fails in the future

    • Allard Vdhooft says:

      It’s great to have a backup plan! If your primer bulb fails, following the steps in the blog post can help you start your chainsaw without it.

  15. Lance Larson says:

    What is the average time it takes to bypass a primer bulb?

    • Allard Vdhooft says:

      You can start a chainsaw without a primer bulb by manually priming it with starter fluid or gasoline. Just follow the steps outlined in the blog post.

  16. Edwin Grant says:

    Great step-by-step guide for bypassing a primer bulb

    • Allard Vdhooft says:

      Thank you for your feedback, Edwin! Starting a chainsaw without a primer bulb can be a useful skill to have in a pinch. Happy cutting!

  17. Cory Arnold says:

    Interesting way to start a chainsaw without a primer bulb

    • Allard Vdhooft says:

      I appreciate your interest in starting a chainsaw without a primer bulb. It’s always good to have alternative methods available. Thank you for reading my blog post!

  18. Lily Berry says:

    I appreciate the visuals in the article, makes it easier to understand

    • Allard Vdhooft says:

      Thank you, Lily Berry! I’m glad the visuals helped you understand starting a chainsaw without a primer bulb. Your feedback is appreciated.

  19. Celina Webb says:

    How does bypassing a primer bulb affect the chainsaw’s longevity?

    • Allard Vdhooft says:

      Bypassing a primer bulb can affect the longevity of a chainsaw. While it may help temporarily, it is advisable to replace the bulb for long-term use.

  20. Julia Sims says:

    Creative solution to a common problem

    • Allard Vdhooft says:

      Thanks for your comment, Julia! I’m glad you found the solution to starting a chainsaw without a primer bulb creative. Hope the information was helpful for you.