How to Fix a Chainsaw That Starts Then Dies When You Give it Gas

Black Max 16 Chainsaw motor

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Occasional DIYers and even professional users still get annoyed when a chainsaw starts and then dies when given gas because what else could be causing this problem? 

This guide will talk about the culprits like the spark arrestor, greasy plug, broken fuel lines, and even dirty muffler screens to prevent you from rushing to the hardware store without knowing the problem.  

Why Does My Chainsaw Die When I Give It Gas?

1. Fuel Supply Issues

Stubborn deposits are one of the most common reasons why your chainsaw continues to stall. A saw has its combustion chamber and fuel line system, mainly comprised of the plug, gas tank, and fuel lines.

Stihl chainsaw and fuel can

These parts get clogged when there are unruly debris and deposits. Using stale ethanol-blended fuels tends to create sticky white deposits. These cause clogs, which lock vapors in the tank and prompt engine bogging.

2. Ignition Problems

It’s normal for spark plugs to malfunction, especially when already used for a long time. Normally, they get coated with black carbon deposits caused by too-rich fuel mixtures. 

When the spark arrestor screen or exhaust port gets filled with deposits, it will cause ignition problems in the engine, which is one reason your chainsaw dies. 

3. High-Speed, Low-Speed, And Idle Screws

Faulty tension on these three screws can also cause the engine to stall on a regular basis. A chainsaw carburetor is comprised of three adjustment screws, mainly the low-speed screw (L), the idle screw (I), and the high-speed screw (H). 

chainsaw High-Speed, Low-Speed, And Idle Screws

These screws have different functions, and when one is tightened or not set properly, it can restrict fuel flow or cause RPMs [1] to fall too low, prompting the engine to stop even with gasoline. 

How to Fix A Chainsaw that Won't Start Properly After Filling it With Gas

Fix #1: Check the filters

Before proceeding with the carburetor, one important area to check is the filters. Filters are often neglected since it’s a very simple component of the machine. 

But dirty filters are a common culprit to saw problems. Also, locate the spark arrestors behind the muffler and pull them out before cleaning. 

Air Filter

Use a screwdriver to detach the cover at the back of your saw. Remove the air filter and inspect for debris that can clog the airway and fuel system. 

Stihl chainsaw clogged air filter

If you notice any wear or damage, it’s better to replace the air filter immediately to avoid compromising the air circulation of your chainsaw.

Fuel Filter

Locate the fuel filter at the bottom of the fuel tank. Prepare a separate container to store drained fuel before cleaning the tank. 

Use a metal wire to brush stale gasoline deposits. Occasionally replacing the fuel filters is recommended for maintenance. 

Fix #2: Examine the carburetor

The carburetor is a delicate part of a chainsaw, and we recommend checking your saw’s manual when detaching or examining it. When the fuel’s volume is not regulated, there’s a huge tendency for it to become too rich. In this case, you’ll have to adjust your carburetor. 

Husqvarna saw clogged carburetor

Clean the carburetor

  1. Detach the air filter. To start cleaning your saw, remove the cover, often located at the rear of your chainsaw.
  2. Take the bowl and bowl nut out of the carburetor. Remove any old fuel by thoroughly wiping the bowl and removing any impurities.
  3. Sprinkle a carburetor cleaner. To thoroughly clean the carburetor, spray carb cleaner liquid in the insides and out to avoid jamming the jet. Check if both ends are cleared by spraying on the other end. If it passes through, then you have already cleared any stuck debris.

Making adjustments to the screws

Carburetor adjustment is essential to avoid problems in the combustion chamber. Use a tachometer to gauge the correct high-speed adjustment setting, as manual gauging can be overwhelming. 

tuning chainsaw carburetor

Rebuilding or replacement

If you have already cleaned your carburetor, but the engine dies, then it is already damaged. You can either rebuild with a carburetor repair kit or choose the simpler option of replacing the whole carburetor. 

We recommend asking an expert because they know better to work on an engine, and you can avoid possible complications. 

Fix #3: Inspect the spark plug

Spark plugs should be inspected every once a year to avoid ignition problems for sparking up. Check for any gaps that could be the culprit to ignition and fuel issues. Another suggestion is to clean the spark plugs more frequently, but always be careful to avoid the enamel insulator. 

chainsaw spark plug

Clean the spark plug

Use a wire brush to clean the spark plug, and remove any excess deposits. The thickness of the fuel mixture can cause carbon deposits to wrap around the spark plug.

Replacement

Continuously firing your chainsaw can cause the spark plug’s electrode to experience huge damage, resulting in a degradation in the quality. When this happens, it’s best to get a new spark plug instead. 

Fix #4: Adjusting the Screws

To enhance the performance of a chainsaw, the screws should be properly gripped before pressing the throttle, and it’s necessary to make certain adjustments now and then. Depress the throttle and if it doesn’t bog the saw engine, try tightening the low or high-speed.

adjusting chainsaw

Low-speed

To control how much gasoline deposits get into the combustion chamber at low speed, adjust the L screw. Gauge and tighten correctly to make sure it’s the right hold.

High-speed

Ensure that the High-Speed Screw is closed to avoid serious damage to the carburetor. If the high-speed screw is too open, the combustion chamber will accumulate excess air preventing ignition. Tweak the L adjustment until it’s sufficient to keep the engine running.

Idle

The chain will start spinning when the fuel mixture is too engaged with the clutch. To avoid such an incident, loosen and adjust the idler screw. Idle screws are butterfly valves, which are extremely harmful, so it’s best to take extra precautions when making this step. 

Makita XCU06T Cordless Chainsaw
Check the Fuel

Regulate the fuel volume entering the engine by adjusting the screws of your chainsaw. Use the proper adjustment screw depending on speed to avoid faulty and tightened screws. 

Other Possible Causes

Vapor Lock

Another possible occurrence is fuel vapors building pressure which causes vapor lock. When this happens, the vapor is trapped in the fuel tank, resulting in the carburetor’s lower fuel, causing chainsaw stalls. Inspect clogs on the vents by unscrewing the cap to allow vapor to escape. 

Air Leak

Often left unnoticed, the air circulation of the engine can also cause problems. Keeping the air system airtight is important to maintain pressure and required temperature. 

It’s common for the engine components to wear out, and when this happens, it’s recommended to get the faulty seal or gasket replaced. Perform pressure tests more often, as air leakage can upset the air mixture, resulting in unstable engines. 

Conclusion

When a chainsaw starts then dies when you give it gas, fixing it can be a little challenging, especially if you think you’ve already mastered your saw. 

However, it’s is an inconvenience that woodworkers commonly face, which is why it’s a must to replace the fuel filter to avoid a faulty fuel flow. 

Robert Johnson is a woodworker who takes joy in sharing his passion for creating to the rest of the world. His brainchild, Sawinery, allowed him to do so as well as connect with other craftsmen. He has since built an enviable workshop for himself and an equally impressive online accomplishment: an extensive resource site serving old timers and novices alike.
Robert Johnson
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