A sputtering engine, difficulty starting, or a complete refusal to run – these are all telltale signs of a gummed-up carburetor on your lawn mower. The carburetor, a vital component responsible for mixing air and fuel in the correct proportions, is susceptible to clogging due to fuel degradation and the accumulation of varnish-like deposits. Fortunately, cleaning a carburetor is a manageable task for the average homeowner, saving you the expense of a professional repair. This comprehensive guide will walk you through the process, step by step, ensuring your lawn mower runs smoothly again.
Understanding the Carburetor’s Role and Why it Gums Up
The carburetor’s primary function is to meter the correct amount of fuel into the air stream entering the engine. This precise mixture is crucial for efficient combustion. When fuel sits unused in the carburetor for extended periods, particularly during the off-season, it can evaporate and leave behind a sticky residue that clogs the tiny passages and jets within the carburetor. This residue, often referred to as “gum” or “varnish,” restricts fuel flow, leading to engine performance issues.
Several factors contribute to carburetor gumming. Old fuel is a major culprit. Gasoline begins to degrade and break down after just a few weeks, forming the sticky deposits we’ve discussed. The ethanol found in most modern gasoline formulations can also exacerbate the problem. Ethanol attracts water, which can lead to corrosion and further fuel degradation. Improper storage of your lawn mower during the off-season also increases the likelihood of carburetor issues. Without proper fuel stabilization or drainage, the fuel remaining in the carburetor is virtually guaranteed to cause problems.
Gathering Your Tools and Materials
Before you begin the cleaning process, it’s essential to gather all the necessary tools and materials. Having everything on hand will streamline the process and prevent unnecessary delays. Here’s a comprehensive list:
- Socket wrench set: For removing the carburetor and other components.
- Screwdrivers (both flathead and Phillips head): Needed for various disassembly tasks.
- Carburetor cleaner: A specialized solvent designed to dissolve gum and varnish. Always use carburetor cleaner in a well-ventilated area.
- Small brushes: Old toothbrushes, pipe cleaners, and small parts cleaning brushes are ideal for scrubbing away deposits.
- Compressed air: Essential for blowing out passages and ensuring they are clear. Eye protection is crucial when using compressed air.
- Safety glasses: To protect your eyes from debris and chemical splashes.
- Gloves: To protect your hands from fuel and cleaning solvents.
- Clean rags: For wiping up spills and cleaning parts.
- Small containers: For soaking parts in carburetor cleaner.
- Carburetor rebuild kit (optional): If the carburetor is severely damaged or worn, a rebuild kit may be necessary.
- Fuel stabilizer: For adding to your fuel in the future to prevent gumming.
- Camera or phone: To take pictures during disassembly, aiding in reassembly.
- Paper towels or a tray: To protect your work surface from spills.
Step-by-Step Guide to Cleaning Your Lawn Mower Carburetor
Now that you have your tools and materials, let’s get started with the cleaning process. Remember to work in a well-ventilated area and take your time to avoid damaging any components.
Disconnecting the Spark Plug
The first and most crucial step is to disconnect the spark plug wire. This prevents accidental starting of the engine while you are working on it. Locate the spark plug wire (usually a rubber boot) and pull it firmly away from the spark plug. This will ensure the engine cannot start during the cleaning process.
Removing the Air Filter Assembly
Next, you’ll need to remove the air filter assembly to gain access to the carburetor. The air filter assembly typically consists of a housing, an air filter, and sometimes a pre-cleaner. The method of removal varies depending on the lawn mower model, but usually involves unscrewing a few bolts or clips. Once the fasteners are removed, carefully detach the air filter assembly. Note the orientation of the filter and housing for easier reassembly.
Detaching the Carburetor
Now, you can access and remove the carburetor itself. Before completely detaching it, carefully inspect the fuel lines and throttle linkages connected to the carburetor. Disconnect the fuel lines by gently pulling them off the carburetor fittings. Be prepared for some fuel spillage, so have a rag handy. Next, disconnect the throttle and choke linkages. These are usually small rods or wires that connect the carburetor to the throttle and choke controls. Take photos as you disconnect everything to help you remember how it all goes back together. Once all the connections are detached, carefully remove the carburetor from the engine. It may be held in place by bolts or screws.
Disassembling the Carburetor
With the carburetor removed, you can now disassemble it for cleaning. Place the carburetor on a clean work surface and carefully begin disassembling it. Start by removing the float bowl, which is the small bowl at the bottom of the carburetor that holds the fuel. It is usually held in place by a single bolt or screw. Once the float bowl is removed, you’ll see the float, a small plastic or metal piece that regulates the fuel level in the bowl. Gently remove the float and the float needle valve. The needle valve controls the flow of fuel into the float bowl.
Next, remove any adjustable jets or screws. These jets control the fuel-air mixture and are often located on the side or bottom of the carburetor. Carefully unscrew these jets and set them aside. Again, take photos as you disassemble to ensure proper reassembly. Pay close attention to the location and orientation of all parts. Keep all the parts organized to avoid confusion during reassembly.
Cleaning the Carburetor Components
Now comes the critical step: cleaning all the carburetor components. Start by soaking all the metal parts in carburetor cleaner for at least 30 minutes. This will help to loosen and dissolve the gum and varnish deposits. After soaking, use small brushes, pipe cleaners, and compressed air to thoroughly clean all the passages and jets. Pay particular attention to the tiny openings in the jets, as these are easily clogged. Make sure that you can see light through all the jets after cleaning.
Use the brushes to scrub away any remaining deposits on the carburetor body and float bowl. Rinse all the parts with clean carburetor cleaner and then dry them with compressed air. Inspect each part carefully for any signs of damage or wear. If any parts are damaged, they should be replaced.
Reassembling the Carburetor
Once all the parts are clean and dry, you can begin reassembling the carburetor. Refer to your photos and notes from the disassembly process. Start by reinstalling the adjustable jets and screws. Make sure they are snug but not over-tightened. Next, reinstall the float and float needle valve. Ensure the float moves freely and the needle valve seats properly. Reattach the float bowl to the carburetor body, tightening the bolt or screw securely.
Reattaching the Carburetor
With the carburetor reassembled, you can now reattach it to the engine. Carefully reattach the throttle and choke linkages, ensuring they are properly connected and move freely. Reconnect the fuel lines to the carburetor fittings. Make sure the fuel lines are securely attached and there are no leaks. Bolt or screw the carburetor back onto the engine, tightening the fasteners securely.
Reinstalling the Air Filter Assembly
Reinstall the air filter assembly, making sure the air filter is clean and properly positioned. Secure the air filter assembly with the bolts or clips you removed earlier.
Reconnecting the Spark Plug
Finally, reconnect the spark plug wire to the spark plug. Make sure the connection is secure.
Testing and Adjusting the Carburetor
After reassembling everything, it’s time to test the engine. Start the engine and let it run for a few minutes. If the engine starts and runs smoothly, congratulations! You have successfully cleaned the carburetor. However, if the engine still runs rough or stalls, you may need to adjust the carburetor.
Most lawn mower carburetors have one or two adjustable jets that control the fuel-air mixture. Adjust these jets until the engine runs smoothly and efficiently. The optimal setting will vary depending on the engine and altitude. Consult your owner’s manual for specific instructions on adjusting the carburetor.
If you are still experiencing problems after cleaning and adjusting the carburetor, it may be necessary to replace the carburetor or seek professional assistance. Sometimes, the damage or wear is too severe to be repaired with simple cleaning.
Preventing Future Carburetor Problems
Preventing future carburetor problems is much easier than dealing with a gummed-up carburetor. Here are some tips to help you keep your lawn mower running smoothly:
- Use fuel stabilizer: Add fuel stabilizer to your gasoline, especially when storing your lawn mower for extended periods. Fuel stabilizer prevents fuel degradation and the formation of gum and varnish deposits.
- Drain the fuel tank: If you are storing your lawn mower for the off-season, drain the fuel tank and run the engine until it stalls. This will remove any remaining fuel from the carburetor and prevent it from gumming up.
- Use fresh fuel: Avoid using old or stale fuel. Gasoline begins to degrade after just a few weeks, so it’s best to use fresh fuel whenever possible.
- Store your lawn mower properly: Store your lawn mower in a clean, dry place. This will help to prevent corrosion and other damage.
- Run the engine periodically: If you are not using your lawn mower regularly, run the engine for a few minutes every few weeks to keep the fuel flowing and prevent it from stagnating.
- Consider using ethanol-free fuel: Ethanol-free fuel is less prone to degradation and water absorption, which can help to prevent carburetor problems.
By following these tips, you can significantly reduce the likelihood of carburetor problems and keep your lawn mower running smoothly for years to come.
When to Seek Professional Help
While cleaning a lawn mower carburetor is a manageable task for many homeowners, there are times when it’s best to seek professional help. If you’ve tried cleaning the carburetor yourself and the engine still isn’t running properly, there may be other underlying issues that require specialized knowledge and tools.
If the carburetor is severely damaged or corroded, it may be beyond repair and require replacement. Similarly, if you are not comfortable disassembling and reassembling the carburetor, it’s best to leave it to a professional. Incorrect reassembly can lead to further damage and costly repairs.
Finally, if you suspect there are other engine problems, such as a faulty ignition system or compression issues, it’s best to consult a qualified mechanic. They can diagnose the problem accurately and recommend the appropriate repairs.
Why does a lawn mower carburetor get gummed up in the first place?
A lawn mower carburetor gets gummed up primarily due to the evaporation of gasoline left sitting in the carburetor bowl for extended periods, especially during the off-season. As gasoline evaporates, it leaves behind a sticky residue composed of heavier hydrocarbons and additives. This residue accumulates in the carburetor’s jets, passages, and bowl, restricting fuel flow and causing the engine to run poorly or not at all.
The severity of the gumming depends on factors such as the type of gasoline used, the length of time the mower sits idle, and the storage conditions. Gasoline containing ethanol is more prone to absorbing moisture, which can accelerate the formation of gum and varnish. Regular use of a fuel stabilizer can help prevent gum formation, especially during periods of inactivity.
What tools and supplies will I need to clean a gummed-up carburetor?
To effectively clean a gummed-up carburetor, you’ll need a few essential tools and supplies. These include a socket wrench set or adjustable wrench for removing the carburetor, carburetor cleaner spray, small brushes (like toothbrush or parts cleaning brush), a set of carburetor cleaning picks or fine wire, a clean workspace, and safety glasses. You may also want to have a digital camera handy to document the disassembly process.
Additionally, consider having some replacement parts on hand, such as a new carburetor gasket or O-rings, as these can sometimes be damaged during removal. A can of compressed air can also be beneficial for drying the carburetor components after cleaning and ensuring all passages are clear. A repair manual or the lawn mower’s owner’s manual can also prove helpful.
Is it possible to clean a carburetor without removing it from the lawn mower?
While a thorough cleaning generally requires removing the carburetor, a partial cleaning can sometimes be performed while it’s still attached to the lawn mower. This involves spraying carburetor cleaner directly into the carburetor throat and air intake while the engine is running or attempting to start. This can sometimes dissolve minor gum deposits and improve engine performance.
However, cleaning the carburetor without removal is typically less effective and doesn’t allow for proper inspection and cleaning of all the internal components, particularly the jets and fuel bowl. This method is more of a quick fix and might not address more severe gumming issues, which necessitate a complete disassembly and cleaning.
How do I properly disassemble the carburetor for cleaning?
Before disassembling the carburetor, take pictures of the assembly for reference during reassembly. Carefully disconnect the fuel line and any linkages attached to the carburetor. Loosen and remove the bolts or screws securing the carburetor to the engine. Once removed, carefully separate the carburetor bowl from the main carburetor body.
As you disassemble, pay close attention to the placement of gaskets, O-rings, and small parts. Clean each component individually using carburetor cleaner and small brushes. Use carburetor cleaning picks or fine wire to clear out any blocked jets or passages. Ensure all parts are thoroughly cleaned and dried before reassembly.
What is the best way to clean the carburetor jets?
Carburetor jets are critical components with very small openings, so cleaning them properly is crucial. The best method is to use carburetor cleaner spray and specialized carburetor cleaning picks or fine wire to carefully clear any blockages. Soak the jets in carburetor cleaner for a few minutes to loosen deposits, then gently probe the openings with the cleaning tool.
Avoid using overly aggressive tools that could damage or enlarge the jet orifices, as this will affect the fuel-air mixture and engine performance. After cleaning, use compressed air to blow out any remaining debris and ensure the jets are completely clear. Inspect the jets for any signs of damage or wear and replace them if necessary.
How do I reassemble the carburetor after cleaning?
Reassembling the carburetor is essentially the reverse of disassembly. Consult the photos you took earlier to ensure all parts are properly positioned. Install the jets, needle valve, and float, ensuring they are correctly aligned and functioning smoothly. Replace any worn or damaged gaskets and O-rings to prevent fuel leaks.
Reattach the carburetor bowl to the main body, tightening the screws or bolts securely. Reconnect the fuel line and any linkages to the throttle and choke. Finally, reattach the carburetor to the engine, ensuring it’s properly secured and sealed. Before starting the engine, double-check all connections to avoid leaks and ensure proper operation.
What if cleaning the carburetor doesn’t fix the lawn mower’s problem?
If cleaning the carburetor doesn’t resolve the issue, other potential problems could be affecting the lawn mower’s performance. These include a faulty spark plug, a clogged air filter, a malfunctioning ignition coil, or a compression issue within the engine cylinder. Additionally, check the fuel lines for cracks or blockages.
If you’ve ruled out these simpler issues, it might be necessary to consult a qualified small engine mechanic for further diagnosis and repair. A professional can assess the engine’s overall condition and identify any underlying problems that are preventing it from running properly. They may also have specialized tools and equipment for more complex repairs.