Hey guys! So, you've got a John Deere S120 lawn mower, and it's giving you some trouble? Don't worry, you're not alone! These mowers are pretty popular, and with a little know-how, you can often fix the common issues yourself. This guide is designed to help you do just that. We'll dive into some of the most frequent problems and how to troubleshoot them. Before we get started, remember to always prioritize safety. Disconnect the spark plug wire before you start any work on your mower. Okay, let's get rolling!

Common Problems with John Deere S120 Lawn Mowers

Engine Won't Start

One of the most frustrating things is when your John Deere S120 just won't fire up. There could be several reasons for this, so let's break it down. First, check the basics: Is there gas in the tank? Sounds obvious, but it's a common oversight. Next, make sure the battery is charged and that the connections are clean and secure. Corroded terminals can prevent a good electrical connection. If the battery seems fine, inspect the spark plug. Remove it, check for any fouling, and make sure it's properly gapped. A bad spark plug is a frequent culprit. If the spark plug looks good, then it could be a fuel issue. Check the fuel filter for clogs. If the fuel isn't flowing correctly, the engine won't start. You might need to clean or replace the filter. Then, inspect the carburetor. Sometimes, it gets gunked up, preventing fuel from entering the engine. You might need to clean the carburetor or, in some cases, rebuild it. Finally, there could be an issue with the safety switches. These switches prevent the engine from starting if the operator isn't in the seat or if the blades are engaged. Make sure all the switches are functioning correctly.

To troubleshoot the engine start, start with the easiest fixes first and work your way up. Always begin by checking the fuel, spark, and air. If those are all fine, then you can move on to more complicated components, like the carburetor, or more in-depth electrical troubleshooting. If you're not comfortable working on engines, it's always a good idea to consult a professional mechanic. They have the expertise and the tools to diagnose and fix the problem efficiently. Don't forget to consult the owner's manual for specific instructions and diagrams for your John Deere S120. This manual can be a great help with finding the parts and providing the steps required to repair your lawnmower. Additionally, ensure that you have the right tools, like the proper socket wrench and spark plug wrench. You can also watch a variety of videos online to help you with the repair, but be sure they are specific to the model you have.

Engine Starts but Dies

Alright, so your John Deere S120 engine starts, but then it quickly dies. This is often a fuel delivery or air intake problem. The first thing you'll want to check is the fuel filter. As we mentioned earlier, a clogged fuel filter can restrict the flow of fuel, causing the engine to starve and die. Replace the fuel filter if necessary. Next, check the fuel line for any kinks or blockages. Make sure that fuel is freely flowing from the tank to the carburetor. Then, we look at the carburetor. A dirty or improperly adjusted carburetor can also cause the engine to die. You might need to clean the carburetor or adjust the idle mixture. Air leaks are another common culprit. Check the intake manifold for cracks or loose connections. Any air leaks can disrupt the air-fuel mixture, causing the engine to stall. Also, check the air filter. A dirty or clogged air filter restricts airflow, which is critical for engine performance. Clean or replace the air filter. Finally, check the fuel cap. If it is not venting properly, it can create a vacuum in the fuel tank, preventing fuel from flowing. The fuel cap is a crucial component to make sure the John Deere S120 runs smoothly.

When troubleshooting this issue, follow the same method as above: check the easy stuff first, such as fuel and air, and then move on to more complex components. If you are not sure where to start, you can take it to a professional. Don't forget that consistent maintenance, like changing the oil, can prevent many of these issues. Maintaining the John Deere S120 properly will ensure a longer lifespan, and fewer repair needs.

Mower Doesn't Cut Evenly

Uneven cutting is another frequent complaint. This is usually caused by a problem with the mower deck. Start by checking the blades. Are they dull, bent, or damaged? If so, you'll need to sharpen or replace them. Make sure you use the correct replacement blades for your John Deere S120 model. Next, check the mower deck. Is it level? If not, you'll need to adjust the deck to ensure an even cut. Refer to your owner's manual for instructions on how to level the deck. Another common issue is that the deck belt might be worn or damaged. Check the belt for cracks, wear, or fraying. Replace the belt if necessary. Also, inspect the spindles. These are the components that hold the blades. Make sure the spindles are in good condition and that they spin freely. If a spindle is damaged, it will also affect your cut. The bearings are also a part of the spindle. Make sure they are not worn or dry.

Maintaining the mower deck is very important for the look of your lawn. The blades should be sharp, and the deck should be level. It's often helpful to measure the deck from the ground to make sure that the mower is level. Also, make sure that the tire pressure is correct. Using the right tire pressure will help ensure that the deck is level. Remember to always use the right parts for your John Deere S120. Not using the correct parts could lead to damage or malfunction of your mower. Be careful when working with the blades. Always disconnect the spark plug wire and wear gloves to protect your hands.

Transmission Problems

If your John Deere S120 is having transmission issues, it can be a real pain. The most common problem is that the mower won't move, or it moves very slowly. Often, this is a result of a broken or worn-out transmission belt. Inspect the belt for damage and replace it if necessary. Another problem is the transmission oil. Check the oil level and add oil if necessary. It's also possible that the transmission itself is damaged. This might involve internal gears or other components. If this is the case, you will likely need to consult with a professional mechanic. Another potential issue is the hydrostatic transmission. This type of transmission uses hydraulic fluid to move the mower. Make sure that the fluid level is correct and that there are no leaks.

Transmission problems can be complex, and it is usually recommended to seek the help of a professional. If you are comfortable working on your mower, consult your owner's manual. The manual has diagrams and instructions on how to maintain the transmission on your John Deere S120. Always ensure that you have the right tools and safety equipment. Remember that if the transmission is damaged, the cost of repair might be high. It is always wise to perform maintenance and inspections. The best way to prevent issues with the transmission is regular maintenance, including changing the oil and inspecting the belts. Take it to a professional if you're not sure how to resolve a transmission issue.

Troubleshooting Tips for Your John Deere S120

Basic Tools and Safety

Before you start, make sure you have the right tools. You'll likely need a set of wrenches, screwdrivers, a socket set, pliers, and possibly a multimeter. Always wear safety glasses and gloves when working on your John Deere S120. Disconnect the spark plug wire before starting any work. Work in a well-ventilated area, and never work on the mower when the engine is hot. Safety is always a must!

Using the Owner's Manual

Your owner's manual is your best friend. It contains valuable information, including troubleshooting guides, diagrams, and parts lists. If you don't have a copy, you can usually find one online. The manual will tell you everything you need to know about the John Deere S120.

Regular Maintenance

Regular maintenance is key to keeping your John Deere S120 running smoothly. This includes changing the oil, replacing the air filter, cleaning or replacing the spark plug, and checking the belts. Following the maintenance schedule in your owner's manual will prevent many problems.

When to Call a Professional

Sometimes, the problems are beyond your skill level or the tools you have. Don't hesitate to call a professional mechanic. They have the expertise to diagnose and fix complex issues. Especially if you're uncomfortable working on engines or transmissions, it's always best to have a professional handle it.

Conclusion

Maintaining your John Deere S120 doesn't have to be a headache. By following these tips and taking a proactive approach to maintenance, you can keep your mower running for years to come. Remember to prioritize safety and consult your owner's manual whenever needed. Happy mowing, guys!