John Deere L120 Problems

The John Deere L120 riding lawn mower, a popular choice for homeowners with medium-sized lawns, offers a blend of power and convenience. However, like any machine subjected to regular use and varying environmental conditions, the L120 isn't immune to its share of problems. Understanding these common issues, their causes, and potential solutions can save you time, money, and frustration, keeping your lawn looking its best.

Starting Troubles? Let's Diagnose the L120's Ignition Woes

One of the most frequent complaints among John Deere L120 owners revolves around starting difficulties. This can manifest in several ways: the engine cranks but doesn't fire, it refuses to crank at all, or it starts roughly and stalls quickly. Pinpointing the exact cause requires a systematic approach.

The Battery's the Boss: Begin by checking the battery. A weak or dead battery is the most common culprit. Use a multimeter to test the voltage – it should read at least 12.6 volts when fully charged. If the voltage is low, try charging the battery with a trickle charger. If the battery won't hold a charge, it's time for a replacement. Also, inspect the battery terminals for corrosion. Clean them with a wire brush and apply a terminal protector spray to prevent future buildup.
Fuel System Follies: Fuel delivery problems are another prime suspect. Start by ensuring there's fresh fuel in the tank. Old or stale gasoline can gum up the carburetor and fuel lines. If the fuel is old, drain the tank and replace it with fresh fuel. Next, check the fuel filter. A clogged fuel filter restricts fuel flow to the carburetor. Replace the fuel filter annually or more often if you mow in dusty conditions. The fuel lines themselves can also become cracked or brittle over time, leading to leaks and air intake. Inspect them carefully and replace any damaged lines.
Spark Plugs and Ignition Coils: A faulty spark plug or ignition coil can prevent the engine from firing. Remove the spark plug and inspect it. Look for signs of fouling (carbon buildup), cracking, or damage. Clean the spark plug with a wire brush or replace it if necessary. To test the ignition coil, use a spark plug tester. If the coil isn't producing a strong spark, it needs to be replaced.
Safety Switch Snafus: John Deere mowers are equipped with safety switches that prevent the engine from starting unless certain conditions are met. These switches are located on the seat, brake pedal, and blade engagement lever. A faulty safety switch can prevent the engine from starting, even if everything else is in good working order. Test each switch with a multimeter to ensure it's functioning properly. If a switch is faulty, replace it.
Carburetor Conundrums: The carburetor mixes air and fuel to create a combustible mixture. Over time, the carburetor can become clogged with dirt and debris, leading to starting problems. Cleaning the carburetor can often resolve the issue. You can use a carburetor cleaner spray or, for more severe cases, remove the carburetor and disassemble it for a thorough cleaning.

Cutting Concerns: Addressing Mower Deck Issues

Uneven cuts, scalping, and poor grass discharge are common complaints related to the L120's mower deck. These problems can stem from various factors, ranging from dull blades to improper deck leveling.

Blade Basics: Dull or damaged blades are a major contributor to poor cutting performance. Sharpen your blades regularly, ideally every 25 hours of mowing. You can sharpen them yourself using a bench grinder or take them to a professional. Replace blades that are bent, cracked, or excessively worn. Always disconnect the spark plug wire before working on the mower blades.
Deck Leveling Dilemmas: An improperly leveled mower deck can result in an uneven cut. The deck should be level from side to side and slightly lower in the front than in the rear (about 1/4 inch lower in the front). Use a leveling gauge or a ruler to measure the deck height at various points. Adjust the deck hangers as needed to achieve the correct leveling.
Belt Breakdown: The mower deck is driven by a belt that connects the engine to the spindles. A worn or damaged belt can slip, causing the blades to spin slower and resulting in a poor cut. Inspect the belt for cracks, fraying, or glazing. Replace the belt if it shows signs of wear. Also, check the belt tension. The belt should be tight enough to prevent slippage but not so tight that it puts excessive strain on the spindles.
Spindle Snags: The spindles are the bearings that support the mower blades. Over time, the spindles can become worn or damaged, causing the blades to wobble and vibrate. This can lead to an uneven cut and premature blade wear. Check the spindles for play by trying to wiggle the blades. If there's excessive play, the spindles need to be replaced.
Discharge Deficiencies: If the grass isn't being discharged properly, it can clump up and leave an unsightly mess. Make sure the discharge chute isn't clogged. Also, avoid mowing when the grass is wet, as wet grass is more likely to clump. Consider using a mulching kit, which chops the grass into fine pieces and returns them to the lawn as fertilizer.

Transmission Troubles: Dealing with Drive System Problems

The L120's transmission is responsible for transferring power from the engine to the wheels. Problems with the transmission can manifest as slow speeds, loss of power, or difficulty shifting gears.

Belt Issues (Again!): Just like the mower deck, the transmission relies on a belt to transfer power. Inspect the drive belt for wear and tear, and replace it if necessary. Proper belt tension is crucial for optimal performance.
Hydrostatic Woes: The L120 uses a hydrostatic transmission, which provides smooth and variable speed control. Over time, the hydrostatic fluid can become contaminated or leak, leading to performance issues. Check the fluid level and add more fluid if necessary. If the fluid is dirty or contaminated, drain and replace it with fresh hydrostatic fluid. Bleeding the air from the hydrostatic system after changing the fluid is also crucial.
Linkage Lapses: The linkage that connects the transmission to the shift lever can become loose or damaged over time. This can make it difficult to shift gears or maintain a consistent speed. Inspect the linkage for wear and tear, and adjust or replace it as needed.
Internal Ailments: In more severe cases, the transmission itself may be damaged. This can be caused by overloading the mower, improper maintenance, or simply wear and tear. Repairing or replacing a damaged transmission can be a costly and complex undertaking, so it's often best left to a qualified mechanic.

Maintenance Matters: Preventing Problems Before They Start

Regular maintenance is key to preventing many of the problems discussed above. By following a consistent maintenance schedule, you can keep your John Deere L120 running smoothly for years to come.

Oil Changes: Change the engine oil and filter every 50 hours of operation or at least once a year. Use the oil type specified in the owner's manual.
Air Filter Cleaning: Clean the air filter regularly, especially if you mow in dusty conditions. Replace the air filter annually or more often if necessary.
Spark Plug Replacement: Replace the spark plug every 100 hours of operation or at least every other year.
Fuel Filter Replacement: Replace the fuel filter annually.
Greasing: Grease the spindles, steering components, and other moving parts regularly.
Blade Sharpening: Sharpen the mower blades every 25 hours of operation.
Battery Maintenance: Keep the battery terminals clean and protected from corrosion. Check the battery voltage regularly and charge the battery as needed.

Frequently Asked Questions

Why won't my John Deere L120 start? Check the battery, fuel level, spark plug, and safety switches. A dead battery or faulty safety switch are common culprits.
Why is my L120 cutting unevenly? Dull blades, an unlevel deck, or a worn belt can cause uneven cuts. Sharpen or replace your blades and level the deck.
How often should I change the oil in my L120? Change the engine oil every 50 hours of operation or at least once a year. This helps maintain engine health.
What type of fuel should I use in my L120? Use fresh, unleaded gasoline with an octane rating of 87 or higher. Avoid using gasoline that contains ethanol.
How do I level the mower deck on my L120? Use a leveling gauge or ruler to measure the deck height and adjust the deck hangers until the deck is level. The front should be slightly lower than the rear.

Conclusion

Addressing John Deere L120 problems requires a systematic approach, starting with proper diagnosis and followed by appropriate maintenance or repairs. By understanding the common issues and implementing preventative measures, you can ensure your L120 remains a reliable workhorse for years to come, keeping your lawn looking its best. Remember, regular maintenance is the most effective way to prevent future problems.