Your Husqvarna Chainsaw Only Runs With the Choke On

You’re able to start and run your chainsaw, but now you have to keep the choke on to keep it running. Locating the problem and fixing it will prevent larger problems from developing in your Husqvarna chainsaw.

A Husqvarna chainsaw only runs with the choke on when the engine is getting too much air or not enough fuel. This is due to old gas; a punctured or clogged fuel line; a plugged fuel filter fuel vent; a bad carburetor gasket; or a dirty carburetor. A Husqvarna may also need a carburetor adjustment.

Keep reading for instructions on performing a carburetor adjustment. I also explain why certain components will cause you to have to use the choke to keep your Husqvarna chainsaw running.

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Follow all safety instructions provided in your equipment operator’s manual prior to diagnosing, repairing, or operating.Consult a professional if you don’t have the skills, or knowledge or are not in the condition to perform the repair safely.

6 Reasons a Husqvarna Chainsaw Only Runs With the Choke On

Old Gas in a Husqvarna Chainsaw

Fuel restrictions will cause you to have to use the chainsaw with the choke on to restrict airflow so the cylinder is getting the ratio of gas to air it requires.

Old gas sitting in a Husqvarna chainsaw can develop sticky substances and a varnish that clogs fuel components and prevents a sufficient flow of fuel.

When you find you have gas that has been sitting in your saw for a long period of time, it’s best to drain the tank and refill it with a fresh gas and oil mix. Add a fuel stabilizer like Sea Foam or STA-BIL to the fuel to assist with cleaning out the fuel system and reducing moisture.

Once you refill the tank with fresh fuel and a stabilizer, start and run your chainsaw for several minutes to work the treated fuel through the chainsaw to loosen the sticky substances.

Reduce the negative effects of fuel by following these tips:

• Use gasoline with a minimum octane rating of 89.
• Don’t use gasoline with an ethanol content greater than 10%.
• Mix the gasoline with a premium 2-cycle oil at a ratio of 50:1 for Husqvarna 2-cycle chainsaws.
• Store fuel in a dry location.
• Consume the fuel within 30 days before it begins to break down or add a fuel stabilizer to make it last a little longer.

To learn more about the right fuel to use, check out “This is the Type of Gas and Oil to Use in a Husqvarna Chainsaws“.

Plugged Fuel Filter in a Husqvarna Chainsaw

A fuel filter’s function is to keep dirt and other contaminates out of the fuel system. You will find the fuel filter for your Husqvarna chainsaw inside the fuel tank.

It is a small cylinder filter that is attached to the fuel line. When the filter isn’t changed regularly, it can become plugged with dirt. This will restrict the amount of fuel that is able to pass through the filter.

When there isn’t enough fuel to mix with air, you may have to run the chainsaw with the choke partly on to correct the ratio of air mixed with gas so the chainsaw continues to run.

Replace the fuel filter by first taking a clean cloth and wiping around the fuel cap to prevent dirt from falling into the fuel tank. Pull the fuel filter out of the tank. A clean bent wire works well for this.

Pull the Husqvarna fuel filter out of the line and install a new fuel filter. Be careful not to lose the retaining ring. This is the small ring that secures the fuel line to the filter.

Place the filter back inside the fuel tank. Reinstall the fuel tank cap.

Punctured or Clogged Fuel Line on a Husqvarna Chainsaw

The choke may need to be on when the fuel line is clogged preventing a good fuel flow or air is being introduced to the fuel system through a puncture in the fuel line.

When the fuel line is clogged, the clog must be removed. To do this, remove the fuel line from the chainsaw. Spray carburetor cleaner into the line to loosen the clog. Follow by blowing compressed air into the line to remove the clog.

Reinstall the line once the blockage has been removed. If you can’t open up the line or you find the fuel line is dry and cracked, you should replace it with a new one.

Look for a puncture in the line where air can be sucked into the fuel system providing additional air to the cylinder and making the choke necessary to correct the amount of air.

Plugged Fuel Vent on a Husqvarna Chainsaw

There is a small circular vent on a Husqvarna chainsaw. This vent is needed to allow air to pass through it so air is allowed to enter the tank when fuel is used and leave the tank when the fuel tank is filled.

When the fuel tank is unable to vent properly, the tank will build pressure forming a vacuum that will restrict fuel flowing out of the tank. This will reduce the amount of fuel supplied to the carburetor.

To test whether you have a clogged fuel tank vent, place your saw on a level surface, start it, and remove the choke. If it begins to run sluggishly, remove or loosen the fuel cap to allow air into the tank.

When air is able to pass into the tank, the engine should run fine. Reinstall and tighten the fuel cap while allowing the saw to continue to run to try to replicate the issue where the engine begins to run sluggishly and possibly shut off.

Replace a plugged fuel tank vent.

Bad Carburetor Gasket on a Husqvarna Chainsaw

A carburetor gasket, located behind the carburetor, can deteriorate allowing air into the system because the gasket no longer seals correctly. This causes a Husqvarna to run lean when there is more air than fuel in the cylinder than the engine requires.

Access the carburetor and carefully remove the linkages and bolts attached to the carburetor. Remove the carburetor and gasket. Install a new carburetor gasket.

Before you install the carburetor, check it out. You may need to clean it while you have it off the chainsaw.

Dirty Carburetor on a Husqvarna Chainsaw

The carburetor’s function is to regulate the amount of fuel that is mixed with air to form a combustion to start and run your Husqvarna chainsaw. A buildup of varnish and deposits can make the carburetor not correctly perform this function.

If you are a little mechanical you should be able to handle cleaning your carburetor. Clean the carburetor by taking it apart and using carburetor cleaner to remove deposits left behind from old fuel.

If the carburetor does not function after being cleaned, you may need to rebuild it or replace it with a new carburetor.

Carburetor Needs Adjustment on a Husqvarna Chainsaw

The carburetor may need to be adjusted to change the RPMs at idle speed and at full throttle. It may be causing the engine to run lean resulting in the need for the choke to be on.

There are adjustment screws on the carburetor to make these adjustments. You can find these screws on the righthand side of the chainsaw near the pull starter.

The screws are labeled “L” for low-speed “T” for idle speed and “H” for high-speed. Start and let the chainsaw warm up for a few minutes before making adjustments to the carburetor.

Adjusting a Husqvarna chainsaw carburetor:

• Start with the L Screw – With the chainsaw idling, turn the screw clockwise until it seems like it’s going to shut off, and then turn the screw slowly counter-clockwise until you achieve a smooth engine idle. Press the throttle and ensure there is a smooth transition as it revs. Make small adjustments until you find the best setting for a smooth operation.
• Adjust the T Screw: This is to adjust the idle speed so the chain doesn’t move while idling. To ensure the T screw is in the correct position, turn the screw clockwise until the chain just begins to move. Then turn the screw slowly the opposite way or counter-clockwise until the chain stops.
• Adjust the H Screw: This screw adjusts the fuel and air mixture at high RPMs. Turn the screw counter-clockwise until it comes to a stop without forcing it. It should begin running sluggish. Slowly turn the screw clockwise until the engine begins to run smoothly. Press the throttle to make sure it accelerates smoothly. Do not over-adjust and try to run at the highest RPMs possible or you could end up damaging the engine.

Many Husqvarna chainsaws have limiter caps to prevent the user from adjusting the carburetor too much. Some chainsaws also require special tools to adjust the carburetor.

If you continue to have problems with the carburetor and are unable to adjust it or unsure how to adjust it, contact your local Husqvarna dealership for help.