The sweet symphony of a smoothly running lawn mower is a gardener’s delight. But what about that frustrating, erratic behavior when your mower suddenly starts revving up and down, like a motorbike on a rollercoaster? It’s more than just an annoyance; it can signal underlying problems that need attention. This article will explore the common culprits behind this maddening lawn mower symptom, providing insights into troubleshooting and potential solutions.
In a nutshell, a lawn mower revving up and down, also known as “hunting,” is often a symptom of a faulty carburetor, a clogged air filter, or a problem with the engine’s governor. It can also be caused by an issue with the fuel delivery system or a failing ignition system. Let’s delve deeper into each of these possibilities.
The Carburetor: The Heart of the Fuel System
The carburetor is the key player in the lawnmower’s fuel delivery system. It mixes air and fuel in precise proportions for combustion. A malfunctioning carburetor can lead to a range of issues, including the revving up and down you’re experiencing.
Dirty or Clogged Carburetor
Over time, dirt, debris, and varnish can accumulate in the carburetor’s jets and passages, hindering fuel flow. This can cause the engine to fluctuate in speed, leading to the hunting behavior.
How to Clean the Carburetor
- Remove the carburetor: Refer to your mower’s manual for specific instructions on how to remove the carburetor.
- Disassemble and Clean: Carefully disassemble the carburetor, paying attention to the jets, passages, and the float. Use a carburetor cleaner to thoroughly clean each part.
- Reassemble and Test: Once clean, reassemble the carburetor and install it back on the engine. Start the engine and see if the revving problem is resolved.
Malfunctioning Float
The carburetor’s float controls the fuel level in the bowl. A faulty float, such as one that’s stuck or not properly adjusted, can result in too much or too little fuel being delivered, leading to the hunting issue.
Float Adjustment
If the float is the culprit, adjusting it might resolve the issue. Consult your mower’s manual for instructions on how to adjust the float level.
The Air Filter: Choking the Engine
The air filter is the first line of defense against dust, debris, and other contaminants entering the engine. A clogged air filter restricts airflow, causing the engine to run lean, potentially leading to hunting.
Inspect and Replace the Air Filter
Regularly check the air filter for dirt buildup. If it’s visibly dirty, it needs replacement.
The Engine Governor: Keeping Things Under Control
The governor is responsible for regulating the engine speed. A faulty governor can lead to a variety of problems, including hunting.
Governor Issues
If the governor is not functioning properly, it may not be able to accurately control the engine speed, causing it to fluctuate.
Troubleshooting the Governor
- Inspect the Governor Linkage: Check for any broken or worn components in the governor linkage.
- Clean and Lubricate: Clean the governor linkage and any moving parts. Apply a light lubricant to ensure smooth operation.
Fuel Delivery System: Getting the Fuel Flow Right
The fuel delivery system ensures that the correct amount of fuel reaches the carburetor. Issues in this system can also contribute to hunting.
Clogged Fuel Line
A clogged fuel line restricts fuel flow, which can cause the engine to fluctuate.
Checking and Cleaning the Fuel Line
Examine the fuel line for any kinks, blockages, or deterioration. If necessary, you can clean the fuel line with a fuel line cleaner.
Dirty Fuel Tank
A dirty fuel tank can introduce debris into the fuel system, leading to clogging and hunting.
Cleaning the Fuel Tank
If your fuel tank is dirty, you can clean it by using a fuel tank cleaner.
The Ignition System: The Spark that Keeps It Going
The ignition system provides the spark that ignites the air-fuel mixture in the engine. Problems in the ignition system can cause the engine to run erratically.
Faulty Spark Plug
A worn or fouled spark plug can lead to a weak spark, causing the engine to misfire and hunt.
Inspect and Replace the Spark Plug
Inspect the spark plug for signs of wear, fouling, or damage. Replace the spark plug if necessary.
Troubleshooting Tips
- Start with the basics: Before diving into more complex repairs, make sure your lawnmower has enough fuel and that the spark plug is connected properly.
- Listen to the engine: Pay attention to any unusual sounds or noises coming from the engine, as these can indicate specific problems.
- Check the fuel line: Ensure the fuel line is not kinked or blocked, preventing proper fuel flow.
- Run a fuel system cleaner: Adding a fuel system cleaner to the gas tank can help to clean out any dirt or debris that may be causing problems.
Final Thoughts
Addressing your lawnmower’s hunting issue can feel like solving a puzzle. By systematically eliminating potential causes and checking components, you can pinpoint the problem and restore smooth operation. Remember, safety should be a top priority when working on your mower. Always consult your owner’s manual for specific instructions and safety precautions. And if you’re unsure about any repairs, it’s best to seek professional help.
FAQ
Here are 7 common FAQs related to lawn mowers that rev up and down:
1. Why is my lawn mower revving up and down when I’m cutting grass?
This is usually a sign of a clogged air filter. The air filter is responsible for preventing dust and debris from entering the engine, and when it gets clogged, it restricts airflow. This can cause the engine to fluctuate in speed as it struggles to get enough air. To fix this, simply remove and clean the air filter.
If cleaning the air filter doesn’t solve the problem, there could be other issues with the carburetor or fuel system. It’s best to take the mower to a mechanic to diagnose and repair any further problems.
2. What if my lawn mower is revving up and down while idling?
If your lawn mower is revving up and down while idling, it could be a sign of a faulty carburetor. The carburetor is responsible for mixing air and fuel, and if it’s not working properly, it can cause the engine to run erratically. This issue can also be related to a clogged fuel filter.
To fix this, you may need to clean or replace the carburetor. If you’re not comfortable doing this yourself, it’s best to take the mower to a mechanic.
3. Can a dirty spark plug cause my lawn mower to rev up and down?
Yes, a dirty spark plug can cause a lawn mower to rev up and down. A spark plug’s job is to ignite the fuel-air mixture, and if it’s dirty or worn, it can cause misfires. This can lead to the engine running erratically.
To fix this, simply clean or replace the spark plug. If you’re not sure how to do this, consult your owner’s manual or take the mower to a mechanic.
4. Could a bad fuel line be causing my lawn mower to rev up and down?
Yes, a bad fuel line can cause a lawn mower to rev up and down. The fuel line delivers fuel from the gas tank to the carburetor, and if it’s cracked or leaking, it can cause the engine to run erratically.
To fix this, you’ll need to replace the fuel line. If you’re not comfortable doing this yourself, take the mower to a mechanic.
5. Is there a problem with my fuel if my lawn mower is revving up and down?
Yes, old or contaminated fuel can cause a lawn mower to rev up and down. Old fuel can break down and clog the fuel system. Additionally, impurities in fuel can also cause engine problems.
To fix this, drain the old fuel and replace it with fresh, clean fuel. If you haven’t used the mower in a while, it’s a good idea to run a fuel stabilizer in the gas tank to prevent the fuel from breaking down.
6. What if my lawn mower is revving up and down after I change the fuel filter?
If your lawn mower is revving up and down after changing the fuel filter, it could be that the new fuel filter is not compatible with your mower. Additionally, a loose connection between the fuel line and the fuel filter can also lead to fuel flow issues.
Make sure you have the right fuel filter for your mower and check for any loose connections in the fuel line. If the problem persists, you may need to consult a mechanic.
7. Is it okay to use a fuel additive to fix my lawn mower’s revving up and down problem?
While some fuel additives can help improve fuel efficiency and performance, they are unlikely to fix a problem with the lawn mower’s engine running erratically. If you’re having trouble with your mower’s engine, it’s best to diagnose the issue and address it directly. Using fuel additives as a solution could potentially mask the underlying problem and lead to further damage in the long run.