The comforting hum of a well-tuned lawnmower is a welcome sound on a sunny day. But what happens when that hum turns into a frantic, erratic revving? A lawnmower that speeds up and slows down seemingly at random can be frustrating and worrisome. This article will delve into the common culprits behind this problem, providing you with the knowledge and troubleshooting steps to get your mower back in tip-top shape. We’ll explore everything from fuel issues to carburetor problems and even electrical quirks, offering clear explanations and practical solutions for restoring your lawnmower’s smooth operation.
In short, a lawnmower that revving up and down is likely experiencing an issue with its fuel system, carburetor, or ignition system. The root cause could be a clogged air filter, a dirty carburetor, a faulty fuel line, or even a spark plug issue. Diagnosing the exact problem requires a methodical approach, examining each potential culprit until the root cause is identified.
Fuel System Troubles: The First Line of Defense
The fuel system is the lifeblood of your lawnmower, delivering the necessary fuel to power the engine. A problem in this area can lead to erratic engine behavior, including revving up and down.
1. Fuel Quality and Storage
- Old Fuel: Fuel degrades over time, losing its volatility and accumulating harmful deposits. If you’ve been storing your mower for a while, the fuel in the tank may be the culprit.
- Contaminated Fuel: Debris, water, or other contaminants can enter the fuel tank, leading to engine problems. Always use fresh, clean fuel.
Solution: Drain the old fuel and replace it with fresh, high-octane gasoline. Consider adding a fuel stabilizer to prevent future degradation if you’re storing the mower for an extended period.
2. Fuel Lines and Filters
- Clogged Fuel Lines: Over time, fuel lines can become clogged with debris or deposits.
- Blocked Fuel Filter: The fuel filter is designed to trap contaminants, but it can become clogged, restricting fuel flow.
Solution: Inspect the fuel lines for blockages and replace them if necessary. Similarly, check the fuel filter and replace it if it appears dirty or blocked.
The Carburetor: The Heart of Your Engine
The carburetor is the intricate part responsible for mixing fuel and air, creating the combustible mixture needed to power your lawnmower. When the carburetor malfunctions, it can lead to unpredictable revving.
1. Dirty Carburetor
- Clogged Jets and Passages: Debris and varnish build-up can clog the small jets and passages within the carburetor, disrupting the fuel flow.
Solution: Cleaning the carburetor is a common fix. You can do this yourself with a carburetor cleaner kit or have it professionally cleaned.
2. Carburetor Adjustments
- Incorrect Settings: The carburetor has adjustable screws that control the fuel-air mixture. If these screws are improperly adjusted, it can cause erratic revving.
Solution: Consult your lawnmower’s manual for the correct settings. If you’re not comfortable adjusting the screws yourself, take it to a mechanic.
The Spark Plug: Igniting the Fire
The spark plug is responsible for igniting the fuel-air mixture, setting the engine in motion. A faulty spark plug can cause inconsistent ignition, leading to revving problems.
1. Fouled Spark Plug
- Carbon Buildup: Over time, carbon deposits can build up on the spark plug electrodes, hindering spark performance.
Solution: Inspect the spark plug. If it appears black or fouled, clean it with a wire brush or replace it with a new one.
2. Worn Spark Plug
- Deterioration: After extended use, spark plugs can wear out, leading to weak sparks.
Solution: If the spark plug is old or worn, replace it with a new one of the appropriate type for your lawnmower.
Electrical System Glitches
While less common, electrical issues can also contribute to erratic revving.
1. Loose or Corroded Connections
- Intermittent Contact: Loose or corroded wires and connections can interrupt the flow of electricity to the ignition system.
Solution: Inspect all electrical connections, tightening any that are loose and cleaning any corrosion.
2. Faulty Ignition Coil
- Weak Spark Output: The ignition coil generates the high voltage needed to create the spark. A faulty coil can produce weak sparks, leading to engine problems.
Solution: Test the ignition coil using a multimeter. If it fails, replace it with a new one.
Diagnosing and Troubleshooting: A Step-by-Step Guide
When your lawnmower is revving up and down, a systematic approach to diagnosing the problem is essential. Here’s a step-by-step guide to help you isolate the culprit:
- Check the Fuel: Start by examining the fuel in the tank. If it’s old or contaminated, drain and replace it.
- Inspect the Fuel Lines and Filter: Look for any blockages in the fuel lines and replace the fuel filter if it’s dirty.
- Examine the Carburetor: Inspect the carburetor for signs of debris or varnish build-up. Clean it or have it professionally cleaned.
- Adjust Carburetor Settings: Double-check the carburetor adjustments based on your lawnmower’s manual.
- Check the Spark Plug: Inspect the spark plug for carbon buildup or wear. Clean or replace it as needed.
- Inspect Electrical Connections: Examine all electrical connections for looseness or corrosion. Tighten or clean as necessary.
- Test the Ignition Coil: If you suspect a faulty coil, test it using a multimeter.
Preventative Maintenance: Keeping Your Mower Running Smoothly
While troubleshooting revving problems can be frustrating, preventative maintenance is key to avoiding them in the first place.
- Regular Maintenance: Follow your lawnmower’s maintenance schedule, including regular oil changes, air filter replacement, and spark plug inspections.
- Fuel Storage: Use fuel stabilizer when storing your mower for extended periods.
- Cleanliness: Keep your mower clean and free of debris, especially around the carburetor and air intake.
Conclusion: Back to a Smooth Ride
A lawnmower that’s revving up and down is a clear sign that something is amiss. By understanding the potential culprits and following a methodical troubleshooting approach, you can diagnose and address the issue, restoring your mower to its smooth-running glory. Remember, preventative maintenance is your best ally in preventing these problems and ensuring many seasons of effortless mowing.
FAQ
Why is my lawnmower revving up and down?
This is a common problem with lawnmowers, and it’s usually caused by a few simple issues. The most common culprits are a dirty carburetor, a clogged air filter, or a problem with the spark plug. If your lawnmower is revving up and down, you should first check these components. If the problem persists, you may need to take your mower to a qualified mechanic for repair.
What are the signs of a dirty carburetor?
A dirty carburetor can cause a variety of problems, including revving up and down, stalling, and difficulty starting. If your lawnmower is experiencing any of these symptoms, you should clean the carburetor.
How do I clean a carburetor?
To clean your lawnmower’s carburetor, you will need to remove it from the engine and disassemble it. Once you have disassembled the carburetor, you can clean it using a carburetor cleaner and a soft brush. Be sure to wear safety goggles and gloves when working with carburetor cleaner, as it is a flammable and toxic substance.
What are the signs of a clogged air filter?
A clogged air filter can restrict airflow to the engine, causing it to run poorly. If your lawnmower is revving up and down, you should check the air filter. If it is dirty or clogged, you should replace it.
What are the signs of a bad spark plug?
A bad spark plug can cause a variety of problems, including revving up and down, stalling, and difficulty starting. If your lawnmower is experiencing any of these symptoms, you should check the spark plug. If it is fouled or damaged, you should replace it.
How do I check the fuel lines?
Fuel lines can become cracked or clogged over time, which can restrict fuel flow to the engine. To check your fuel lines, you should look for any cracks or leaks. You should also check for any blockages in the fuel lines.
How do I know if the problem is with the engine?
If you have checked the carburetor, air filter, and spark plug and the problem persists, the problem may be with the engine itself. You should take your lawnmower to a qualified mechanic for diagnosis and repair.