Can You Start a Chainsaw without Primer Bulb?

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This is one question that often comes up especially when troubleshooting chainsaws. If the engine refuses to rev after multiple tries, we check the primer bulb. If it is broken the usual recommendation is to replace it. But is it possible to use a chainsaw minus a primer bulb? Yes, and this guide shows you how it is done.

The primer bulb pumps gas from the tank into the carburetor and helps when starting a chainsaw cold. You can run the saw without the primer bulb by closing the line that links it to the carburetor. Add fuel to the carburetor, pull the starter rope and the engine will start.

Can You Run a Chainsaw without a Primer Bulb?

Yes, you can use a chainsaw even if the primer bulb is damaged. The following is a step by step guide on how to do this.

If the primer bulb is damaged or you do not want to use it, bypassing is easy enough. The primer bulb works through the line that joins it to the carburetor. By shutting down this line and adding fuel to the engine or the air filter, you can start the chainsaw. You can also use starter fluid.

Just to be clear: if your chainsaw has a primer bulb and it is not working, the best option is to replace it. But if you do not have a replacement on hand and you need to use the chainsaw now, you can try this.

Required Tools and Materials

  • Starter fluid (the Sta-bil 11 0z. is goi g to work fine)
  • Screwdriver
  • Safety goggles
  • Gloves

Do this outdoors in a well-ventilated or open area. Put your eyewear protection and gloves before attempting to fix the chainsaw.

Step 1: Prepare the Chainsaw

Turn off the chainsaw. Inspect the spark plug, air filter, fuel filter, fuel line, muffler and carburetor. Look at the wiring and connections. If everything looks good, open the fuel reservoir. Make sure that it is filled.

Doing a preliminary checkup is necessary to eliminate other possible reasons why your chainsaw is not running. Once you have ruled out all the other possibilities you can check the primer bulb.

Step 2: Test the Primer Bulb

Look for the primer bulb. Usually it is below the carburetor. Yours might be somewhere else so refer to your manual. You can tell it is the bulb by the red or black color.

Look at the bulb closely. If there is a tear, warping or any sign of damage, replace it. If there is none, press the bulb thrice. This will start the process which will send fuel to the carburetor.

Set the choke lever to full power. Pull the starter rope 4 times. If the engine starts you are done. If it does not, proceed to the next step.

Step 3: Add Starter Fluid or New Fuel

Look for the air filter. Usually it is on the side. Lift the cover off or remove the screws holding the cover in place. Remove the entire filter from the chainsaw. Use a screwdriver or wrench to remove the screws or bolts. Store them in a safe place so you can put the cover back on.

Check the air filter for signs of damage or dirt. Replace the filter if damaged and clean if dirty. Soapy water will be enough. Set the filter aside for now and wait for it to dry.

With the air filter removed, you can pour the starter fluid into the hole. Do not pour a lot as it might cause some damage. If you want to be more cautious, pour a 50:1 gas oil mix. Some chainsaws require a 40:1 mix so make sure the ratio is correct.

Once you have added the starter fluid or gas oil mix, put the air filter cover back on. Put the screws and bolts back on.

Step 4: Start the Chainsaw

Once the cover is set, turn the chainsaw on as you normally do. Pull the cord at least six times until the engine catches on. When it does you can start using the chainsaw.

Using a chainsaw without a chain brake is not a good idea, but as shown here, it is possible to run a chainsaw without the primer bulb. If the chainsaw is not performing the way it usually does, make some to the carburetor.

Is it Safe to Run Chainsaws without a Primer Bulb?

If your chainsaw has a large engine it does not need a primer bulb. This feature is limited to small engines that require assistance in starting. If your chainsaw does not have a primer bulb it is not required.

Most small engine chainsaws benefit from a primer bulb. It makes starting easy at low temperature for one thing. But you can bypass this feature if you do not need it. But keep in mind that some chainsaws will require this component.

If the primer bulb is damaged, you add fuel into the carburetor. Pour the fuel via the air intake hole and pull the cord. If that does not work, clean the carburetor first. Sometimes cleaning the carburetor is all that is needed to get the primer bulb going again.

To do this, unscrew the cover for the fuel line. Once you see the fuel lines, disconnect the cable joining the line to the carburetor. Put any small object on the line to block it. Hook the line to the carburetor and you are done. You have bypassed the primer bulb.

You can start the chainsaw, but it will require more power especially in cold weather. Adjust the H and L setting on the carburetor to improve performance.

To keep things simple, here are the basic guidelines:

Chainsaws with a 35cc or larger engine do not have a primer bulb. It is safe to run the tool without it. The Farmac F380W is a 72cc chainsaw, so no primer bulb there.

Chainsaws with a small engine often have a primer bulb. But you can run the saw without this feature. There are ways to bypass it. The primer bulb can be replaced if damaged. But you can safely start the saw without it.

Adding fuel to start your chainsaw is called manual priming. It definitely works but it can get tiresome if you have to do it repeatedly. It is more practical to replace the primer bulb or get a high end chainsaw that does not need it.

Do All Chainsaws Need a Primer Bulb?

Chainsaws with a 35cc or larger engine do not have a primer bub. Smaller engines usually have it installed to speed up cold starts.

Large engines do not need this part because there is enough power to ignite the engine. If the engine is 35cc or less, a primer bulb can help. Basically what it does is supply gas to the carburetor and give the engine a boost.

This is how a primer bulb works. When it is activated the bulb extracts fuel from the reservoir. This fuel is transmitted into the carburetor. When you pull the starter pulley, the fuel moves from the carburetor into the engine. Combustion follows and the chainsaw comes to life.

Engines larger than 35cc do not require a primer bulb because it receives enough power, even with a cold start. If your chainsaw does not have this part installed, it means the engine is 40cc or larger.

You will find primer bulbs in chainsaws designed for home use. Usually homeowners use their chainsaw for short durations and are stored for months during winter. Since these chainsaws are often started cold, a primer bulb is important.

A primer bulb also eliminates air in the fuel line. The less air present in the fuel line, the smoother fuel goes from the carburetor to the engine. This can help start the engine when it is cold.