John Deere La105 Problems

The John Deere La105 is a popular riding lawn mower known for its reliability and affordability, making it a common choice for homeowners with smaller to medium-sized lawns. However, like any machine, the La105 isn't immune to experiencing problems over time. Understanding these common issues, their potential causes, and how to address them can save you time, money, and the frustration of a lawn that's begging to be mowed.

My La105 Won't Start! What Could Be Wrong?

A non-starting La105 is arguably the most common complaint. Before tearing anything apart, systematically check the basics. It's often the simplest things that are overlooked.

Fuel Issues: The most frequent culprit is stale or contaminated fuel. Gasoline degrades over time, especially when left sitting in the tank for extended periods. Always use fresh fuel, and consider adding a fuel stabilizer, especially before storing the mower for the winter. Also, check the fuel filter. A clogged filter restricts fuel flow and prevents the engine from starting. It's a relatively inexpensive part and easy to replace.
Spark Plug Problems: A faulty spark plug can prevent the engine from igniting the fuel-air mixture. Inspect the spark plug for signs of damage, such as cracks or excessive carbon buildup. Clean the spark plug with a wire brush or replace it altogether. Ensure the spark plug wire is securely connected.
Battery Troubles: A weak or dead battery is another common reason for a no-start condition. Check the battery voltage with a multimeter. A fully charged 12-volt battery should read around 12.6 volts. If the voltage is significantly lower, try charging the battery. If the battery doesn't hold a charge, it may need to be replaced. Inspect the battery terminals for corrosion and clean them thoroughly.
Safety Interlocks: John Deere mowers have safety interlocks that prevent the engine from starting if certain conditions aren't met. These interlocks are typically located on the seat, brake pedal, and blade engagement lever. Make sure the operator is seated, the brake pedal is depressed, and the blade engagement lever is disengaged when attempting to start the mower. Check the switches associated with these interlocks for proper function. A faulty switch can prevent the engine from starting, even if all other conditions are met.
Carburetor Issues: If the mower has been sitting for a while, the carburetor can become clogged with varnish from evaporated fuel. This can restrict fuel flow and prevent the engine from starting. Try using a carburetor cleaner to dissolve the varnish. In severe cases, the carburetor may need to be removed and cleaned thoroughly or replaced.

My Blades Aren't Engaging – What's Going On?

If your La105 starts fine, but the blades won't engage, there are a few potential causes to investigate.

Blade Engagement Cable: The blade engagement cable connects the blade engagement lever to the cutting deck. If the cable is stretched, broken, or disconnected, the blades won't engage. Inspect the cable for damage and ensure it's properly connected at both ends. Adjust the cable tension if necessary.
Electric PTO Clutch: The La105 uses an electric PTO (Power Take-Off) clutch to engage the blades. This clutch is an electromagnetic device that engages the blades when energized. If the clutch is faulty, the blades won't engage. Check the clutch wiring for damage and ensure it's receiving power when the blade engagement lever is activated. Use a multimeter to test the clutch resistance. If the resistance is outside the specified range, the clutch may need to be replaced.
Worn Belts: The belts that drive the blades can become worn or stretched over time, causing them to slip and prevent the blades from engaging properly. Inspect the belts for cracks, fraying, or excessive wear. Replace the belts if necessary. Ensure the belt tension is correct.
Deck Obstructions: Debris, such as sticks, rocks, or grass clippings, can become lodged in the cutting deck and prevent the blades from rotating freely. Inspect the cutting deck and remove any obstructions.

The Engine Runs Rough or Stalls Frequently

A rough-running or stalling engine can be frustrating. Here's what to look for.

Air Filter: A dirty air filter restricts airflow to the engine, causing it to run lean and stall. Inspect the air filter and clean or replace it as needed. A clean air filter is crucial for proper engine performance.
Fuel Filter: As mentioned earlier, a clogged fuel filter can restrict fuel flow and cause the engine to run rough or stall. Replace the fuel filter regularly.
Carburetor: A dirty or clogged carburetor can also cause the engine to run rough or stall. Clean the carburetor or have it professionally cleaned if necessary.
Spark Plug: A faulty spark plug can cause misfires and lead to a rough-running or stalling engine. Replace the spark plug if it's damaged or worn.
Valve Adjustment: Over time, the valve clearances can change, affecting engine performance. Check and adjust the valve clearances according to the manufacturer's specifications. This is a more advanced repair that may require professional assistance.

My La105 Smokes Excessively

Excessive smoke from the exhaust is a sign of a potential engine problem. The color of the smoke can provide clues about the cause.

Blue Smoke: Blue smoke indicates that the engine is burning oil. This can be caused by worn piston rings, valve seals, or a damaged cylinder. These are significant engine repairs that may require professional attention. Check the oil level regularly and add oil as needed.
Black Smoke: Black smoke indicates that the engine is running too rich, meaning it's receiving too much fuel. This can be caused by a dirty air filter, a faulty carburetor, or a stuck choke.
White Smoke: White smoke can indicate that the engine is burning coolant, which could be a sign of a blown head gasket or a cracked cylinder head. This is a serious engine problem that requires immediate attention.

The Mower is Vibrating Excessively

Excessive vibration can be uncomfortable and can also damage the mower over time.

Bent Blade: A bent blade can cause the mower to vibrate excessively. Inspect the blades for damage and replace them if necessary.
Unbalanced Blade: Even if the blades aren't visibly bent, they may be unbalanced. Use a blade balancer to check the balance of the blades. Sharpen the blades to ensure they are properly balanced.
Loose Mounts: Check the engine and deck mounts for looseness. Tighten any loose bolts or replace worn mounts.
Damaged Spindle: A damaged spindle can cause excessive vibration. Inspect the spindles for damage and replace them if necessary.

The Mower Isn't Cutting Evenly

An uneven cut can be frustrating, as it leaves your lawn looking patchy and unkempt.

Uneven Tire Pressure: Ensure that all tires are inflated to the correct pressure. Uneven tire pressure can cause the deck to be uneven, resulting in an uneven cut.
Bent Blade: A bent blade can cause the mower to cut unevenly. Inspect the blades for damage and replace them if necessary.
Dull Blade: Dull blades tear the grass instead of cutting it cleanly, resulting in an uneven cut. Sharpen the blades regularly.
Deck Leveling: The cutting deck may need to be leveled. Refer to the owner's manual for instructions on how to level the deck.
Clogged Deck: Grass clippings can build up under the deck, causing an uneven cut. Clean the deck regularly.

Frequently Asked Questions About John Deere La105 Problems

Why won't my John Deere La105 start? Common causes include stale fuel, a dead battery, a faulty spark plug, or safety interlock issues. Start by checking these basic components.
How often should I change the oil in my John Deere La105? It's recommended to change the oil every 50 hours of operation or at least once a year. Regular oil changes help to prolong the life of the engine.
What type of oil should I use in my John Deere La105? Refer to your owner's manual for the recommended oil type and viscosity. Typically, a 10W-30 or SAE 30 oil is suitable for most conditions.
How do I sharpen the blades on my John Deere La105? You can sharpen the blades using a metal file or a blade grinder. Be sure to maintain the original blade angle and balance the blades after sharpening.
Where can I find parts for my John Deere La105? You can purchase parts from your local John Deere dealer or from online retailers that specialize in lawn mower parts. Always use genuine John Deere parts or reputable aftermarket brands.

In conclusion, while the John Deere La105 is a reliable machine, understanding common problems and their solutions is crucial for maintaining its performance and longevity. By performing regular maintenance and addressing issues promptly, you can keep your La105 running smoothly for years to come.