A gummed-up carburetor is a common culprit behind a lawn mower that refuses to start or runs poorly. The sticky residue left behind by evaporating gasoline can clog the tiny passages within the carburetor, preventing the proper air-fuel mixture from reaching the engine. Fortunately, cleaning a lawn mower carburetor is a manageable task for most homeowners, saving you a trip to the repair shop and potentially extending the life of your mower. This comprehensive guide will walk you through the process, step-by-step.
Understanding Carburetor Gumming and its Effects
Gasoline, especially when left sitting for extended periods, can break down and leave behind a varnish-like substance. This substance, often referred to as “gum,” accumulates in the carburetor’s jets and passages. These passages are precisely calibrated to deliver the correct amount of fuel, and even a small amount of gum can disrupt the flow.
A gummed-up carburetor can manifest in several ways. The most common symptom is difficulty starting the engine. You might find yourself pulling the starter cord repeatedly without any sign of ignition. The engine might start briefly but then stall immediately.
Another symptom is rough running or idling. The engine may surge erratically, sputter, or lack power. You might also notice excessive smoke coming from the exhaust. These problems are all indicative of an improper air-fuel mixture caused by a clogged carburetor.
Ignoring these symptoms can lead to further engine damage. A lean-running engine (too much air, not enough fuel) can overheat and cause damage to the piston, cylinder, and valves. It’s best to address a gummed-up carburetor promptly to prevent more serious issues.
Safety First: Preparing for Carburetor Cleaning
Before you begin, safety is paramount. Gasoline is flammable, and some carburetor cleaning solutions can be harmful.
First, disconnect the spark plug wire. This prevents accidental starting during the cleaning process. Make sure the wire is pulled firmly away from the spark plug and secured so it cannot accidentally reconnect.
Next, drain the fuel tank. You can do this by siphoning the fuel out or by carefully tipping the mower over a suitable container. Dispose of the old fuel properly according to local regulations. Never pour gasoline down a drain or into the environment.
Work in a well-ventilated area. This will help to dissipate any fumes from the gasoline or cleaning solutions. Outdoors is ideal. If you must work indoors, open windows and doors to ensure adequate ventilation.
Gather your supplies. You’ll need carburetor cleaner, a set of small screwdrivers (both flathead and Phillips head), pliers, wrenches, a clean rag, safety glasses, and gloves. Consider having a digital camera or smartphone handy to take pictures of the carburetor before disassembly. This can be helpful when reassembling everything.
Finally, wear safety glasses and gloves. Carburetor cleaner can irritate the skin and eyes.
Removing the Carburetor
Now, let’s get to the removal process. The exact steps may vary slightly depending on the make and model of your lawn mower, but the general procedure is similar.
Start by locating the carburetor. It’s usually mounted on the side of the engine, connected to the air filter and the fuel line. Refer to your lawn mower’s owner’s manual for the precise location.
Disconnect the fuel line from the carburetor. Use pliers to loosen the clamp and gently pull the fuel line off the carburetor fitting. Have a small container ready to catch any residual fuel that may spill.
Remove the air filter housing. This is usually held in place by a few screws or clips. Once the housing is removed, you’ll have better access to the carburetor.
Detach any linkages connected to the carburetor. These linkages control the throttle and choke. Pay close attention to how these linkages are connected, and take pictures if necessary. Carefully disconnect them using pliers or a screwdriver.
Remove the bolts or nuts that secure the carburetor to the engine. These are typically located on the flange where the carburetor mounts to the intake manifold. Once the bolts or nuts are removed, carefully pull the carburetor away from the engine.
With the carburetor removed, you can now proceed to the cleaning stage.
Cleaning the Carburetor: A Detailed Approach
This is the core of the process. Thorough cleaning is essential for restoring proper carburetor function.
First, disassemble the carburetor. This involves removing the float bowl (the small bowl at the bottom of the carburetor), the float, the needle valve, and any adjustable jets. Again, taking pictures during disassembly can be extremely helpful for reassembly.
Inspect all parts for dirt and debris. Pay close attention to the jets, which are tiny brass screws with very small holes. These holes are easily clogged by gum and varnish.
Now, apply carburetor cleaner liberally to all parts. Use the spray nozzle to direct the cleaner into the jets and passages. Let the cleaner soak for at least 15-20 minutes to dissolve the gum and varnish.
After soaking, use a small wire or carburetor cleaning kit to carefully clean out the jets and passages. Be extremely gentle, as the jets are made of soft brass and can be easily damaged. Avoid enlarging the jet holes, as this will affect the engine’s performance.
Rinse all parts thoroughly with carburetor cleaner. This will remove any remaining dirt and debris.
Use compressed air to blow out the jets and passages. This will ensure that they are completely clear of any obstructions. Pay particular attention to the tiny holes in the jets.
Inspect the float and needle valve. The float should be free of any cracks or dents. The needle valve should be clean and sharp. If the float is damaged or the needle valve is worn, replace them.
Clean the carburetor body thoroughly. Use a brush and carburetor cleaner to remove any dirt and debris from the exterior of the carburetor.
Reassembling the Carburetor
With the carburetor cleaned and all parts inspected, it’s time to reassemble everything.
Reinstall the jets. Make sure they are tightened securely, but do not overtighten them, as this can damage the threads.
Reinstall the needle valve and float. Ensure the float moves freely. The float level is crucial, consult your mower’s service manual for the correct float height setting.
Reattach the float bowl. Make sure the gasket is in good condition. If the gasket is damaged, replace it.
Reattach any linkages that were removed. Refer to the pictures you took during disassembly to ensure they are connected correctly.
Reinstall the carburetor onto the engine. Secure it with the bolts or nuts that were removed earlier.
Reconnect the fuel line. Make sure the clamp is tightened securely to prevent fuel leaks.
Reinstall the air filter housing.
Reconnect the spark plug wire.
Starting and Fine-Tuning
After reassembling the carburetor, it’s time to start the engine and see if your efforts have paid off.
First, prime the engine by pressing the primer bulb a few times. This will help to draw fuel into the carburetor.
Pull the starter cord. If the engine starts but runs roughly, you may need to adjust the carburetor settings.
Most carburetors have one or two adjustment screws that control the air-fuel mixture. The exact location and function of these screws will vary depending on the make and model of your lawn mower. Consult your owner’s manual for specific instructions.
Adjust the idle speed screw to achieve a smooth and stable idle.
Adjust the mixture screw to optimize the engine’s performance. The goal is to find the setting that provides the best power and fuel efficiency. Typically, you’ll want to turn the screw in or out until the engine runs smoothly and responds quickly to changes in throttle.
If you’re unsure how to adjust the carburetor settings, it’s best to consult a qualified mechanic.
Preventing Future Carburetor Problems
Once you’ve successfully cleaned your lawn mower carburetor, you’ll want to take steps to prevent future gumming.
The most important thing you can do is to use fresh gasoline. Gasoline can start to degrade after just a few weeks, so it’s best to use fuel that is no more than 30 days old.
Add a fuel stabilizer to the gasoline. Fuel stabilizers help to prevent the formation of gum and varnish. Follow the instructions on the fuel stabilizer bottle.
Drain the fuel tank before storing the lawn mower for the winter. This will prevent the gasoline from sitting in the carburetor and gumming up the jets.
Run the engine until it stalls. This will ensure that there is no fuel left in the carburetor.
Consider using ethanol-free gasoline. Ethanol can attract moisture, which can lead to corrosion and fuel system problems.
By following these tips, you can help to keep your lawn mower carburetor clean and prevent future problems. This will ensure that your lawn mower starts easily and runs smoothly for years to come.
By following these steps, you can often avoid costly repairs and keep your lawn mower running smoothly. Remember to prioritize safety and consult your owner’s manual for specific instructions related to your model.
Why does a lawn mower carburetor get gummed up?
Lawn mower carburetors get gummed up primarily due to old fuel sitting in the carburetor for extended periods. Gasoline contains volatile components that evaporate over time, leaving behind a sticky residue. This residue, often referred to as varnish or gum, can clog the small jets and passages within the carburetor, hindering the proper mixing of fuel and air needed for the engine to run smoothly, or even start at all.
This problem is especially prevalent during the off-season when lawn mowers are stored. The lack of use allows the fuel to degrade and solidify. Furthermore, some modern fuels contain ethanol, which can attract moisture and further contribute to the formation of deposits. This moisture can corrode internal carburetor parts, exacerbating the gumming issue.
What tools do I need to clean a gummed up carburetor?
To effectively clean a gummed-up lawn mower carburetor, you’ll need a few essential tools. These include a set of screwdrivers (both flathead and Phillips head), a socket wrench set, carburetor cleaner spray, a small container for soaking parts, and a set of carburetor cleaning tools (small wire brushes or picks). Safety glasses and gloves are also recommended for protection.
Optional, but helpful, tools include compressed air to blow out passages after cleaning, a digital camera or smartphone to document the disassembly process for reassembly reference, and a parts cleaner solution specifically designed for carburetors. Having a clean workspace is also crucial to prevent parts from getting lost or contaminated.
Is it necessary to completely disassemble the carburetor to clean it?
While a complete disassembly offers the most thorough cleaning, it’s not always strictly necessary, especially if the gumming is minor. Sometimes, spraying carburetor cleaner directly into the carburetor’s air intake and fuel inlet while the engine is running (or attempting to start) can dissolve some of the gum and restore functionality. This is often referred to as a “quick clean” or “carburetor flush”.
However, if the quick clean doesn’t resolve the issue, or if the engine is severely malfunctioning, a full disassembly is recommended. This allows you to access and clean all the jets, passages, and components individually, ensuring that all deposits are removed. Remember to take pictures during disassembly to aid in proper reassembly.
What is the best carburetor cleaner to use?
The best carburetor cleaner to use is one specifically formulated for carburetor cleaning. These cleaners are designed to dissolve varnish, gum, and other deposits effectively without damaging the carburetor’s delicate components. Look for a cleaner that is safe for use on metal and rubber parts. Aerosol sprays are convenient for direct application, while liquid cleaners are suitable for soaking parts.
Avoid using harsh chemicals like brake cleaner or solvents not intended for carburetors, as they may damage seals and other components. When using any carburetor cleaner, always follow the manufacturer’s instructions and wear appropriate protective gear, such as gloves and safety glasses, to prevent skin and eye irritation.
How do I know if my carburetor is beyond repair?
A carburetor might be beyond repair if it has significant physical damage, such as cracks or broken components, especially in the carburetor body itself. Also, if internal passages are severely corroded or blocked beyond cleaning, the carburetor may be irreparable. Attempting to clean a severely damaged carburetor can be futile and potentially more costly than replacement.
Another indicator is when you’ve thoroughly cleaned the carburetor, replaced any worn parts (like gaskets and needles), and the engine still doesn’t run properly or exhibits the same symptoms as before. In such cases, the carburetor’s internal mechanisms may be too worn or damaged to function reliably, making replacement the most practical solution.
What should I do after cleaning the carburetor to prevent future gumming?
After cleaning the carburetor, the best way to prevent future gumming is to stabilize the fuel before storing the lawn mower for extended periods. Fuel stabilizers prevent the gasoline from breaking down and forming varnish or gum. Add the stabilizer to the fuel tank according to the manufacturer’s instructions before storing the mower.
Another helpful practice is to run the lawn mower until it’s completely out of fuel before storing it. This prevents any fuel from sitting in the carburetor and potentially gumming up. Alternatively, you can drain the fuel from the carburetor’s bowl using the drain screw if your model has one. Storing the mower in a dry environment can also help minimize moisture-related corrosion.
Can I use compressed air to clean the carburetor passages?
Yes, using compressed air is an excellent method for cleaning carburetor passages after using carburetor cleaner. Compressed air helps to dislodge any remaining debris or cleaner residue, ensuring the passages are completely clear. Always wear safety glasses when using compressed air to prevent any particles from entering your eyes.
When blowing out the passages, direct the air stream carefully into each jet and port, ensuring air flows freely through the intended path. If you encounter resistance or no airflow, it indicates a blockage that needs further attention. Remember to follow the manufacturer’s guidelines for air pressure to avoid damaging delicate carburetor components.