Kubota Z125S Won’t Start: Reasons and Troubleshooting Steps

Is your Kubota Z125S giving you a hard time when it comes to starting? It can be frustrating and inconvenient when your trusty mower refuses to come to life. Fortunately, there are several common reasons why a Kubota Z125S won’t start, and most of them can be easily resolved. In this article, we will explore the potential causes of starting issues with the Kubota Z125S and provide troubleshooting steps to get your mower up and running again.


The Kubota Z125S is a popular zero-turn mower known for its reliability and performance. However, like any mechanical equipment, it may experience starting problems from time to time. Before diving into the troubleshooting steps, let’s gain a better understanding of this mower and its components.

Understanding the Kubota Z125S

The Kubota Z125S is equipped with a powerful engine designed to provide efficient mowing capabilities. It relies on several key components to start and operate smoothly. These include the fuel tank, spark plug, fuel filter, battery, and ignition switch. Understanding the role of each component is essential in diagnosing the starting issue.

Common Reasons for Kubota Z125S Not Starting

  1. Empty Fuel Tank: One of the primary reasons why your Kubota Z125S won’t start is an empty fuel tank. It’s crucial to ensure an adequate fuel supply before attempting to start the mower.
  2. Faulty Spark Plug: A worn-out or faulty spark plug can prevent the mower’s engine from igniting the fuel-air mixture, leading to starting problems.
  3. Clogged Fuel Filter: Over time, the fuel filter can become clogged with debris and impurities, hindering the flow of fuel to the engine. This can result in starting difficulties or poor performance.
  4. Dead Battery: If the battery is discharged or faulty, it may not have enough power to crank the engine. This can prevent the Kubota Z125S from starting.
  5. Faulty Ignition Switch: A malfunctioning ignition switch can disrupt the electrical connection and prevent the mower from starting.

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Troubleshooting Steps to Get Your Kubota Z125S Started

If your Kubota Z125S refuses to start, you can follow these troubleshooting steps to identify and resolve the issue:

Step 1: Check the Fuel Level

Ensure that the fuel tank has an adequate amount of fuel. If it’s low, refuel before attempting to start the mower. Additionally, check for any signs of fuel leakage or contamination.

Step 2: Inspect the Spark Plug

Inspect the spark plug for signs of wear, damage, or carbon buildup. If necessary, clean or replace the spark plug according to the manufacturer’s recommendations. A healthy spark plug is crucial for the ignition process.

Step 3: Clean or Replace the Fuel Filter

Inspect the fuel filter and clean it if it’s clogged with debris. If cleaning doesn’t improve the situation, consider replacing the fuel filter. Regular maintenance of the fuel filter ensures proper fuel flow to the engine.

Step 4: Test the Battery

Check the battery voltage using a multimeter. If the voltage is low, recharge the battery or replace it if it’s faulty. Ensure the battery terminals are clean and securely connected.

Step 5: Verify the Ignition Switch

Test the ignition switch by turning it on and off. Listen for any clicking sounds or abnormal behavior. If the switch is faulty, it may need to be replaced by a professional.

Step 6: Consult a Professional

If the above troubleshooting steps do not resolve the issue, it’s advisable to consult a professional Kubota technician or authorized dealer. They have the expertise to diagnose and repair complex starting problems.

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Maintenance Tips to Prevent Starting Issues

Prevention is always better than cure. To minimize the chances of starting issues with your Kubota Z125S, follow these maintenance tips:

  • Regularly check the fuel level and refill as needed.
  • Clean or replace the spark plug at regular intervals.
  • Clean or replace the fuel filter according to the manufacturer’s recommendations.
  • Maintain the battery by keeping it charged and periodically checking its voltage.
  • Keep the ignition switch in good condition by operating it gently and ensuring proper functionality.


Q: Why does my Kubota Z125S have difficulty starting in cold weather?

A: Cold weather can affect the starting performance of small engines, including the Kubota Z125S. Cold temperatures make it harder for fuel to evaporate and ignite properly. Using a cold-weather fuel additive or keeping the mower in a warm environment can help alleviate this issue.

Q: Can I jump-start my Kubota Z125S using another vehicle?

A: No, it is not recommended to jump-start a Kubota Z125S using another vehicle. The voltage and electrical systems of different vehicles can vary, and attempting to jump-start the mower may damage its electrical components. It’s best to follow the troubleshooting steps mentioned earlier or consult a professional.

Q: How often should I replace the spark plug in my Kubota Z125S?

A: The spark plug in a Kubota Z125S should typically be replaced every 100 hours of operation or at least once a year, whichever comes first. However, it’s essential to refer to the manufacturer’s guidelines and consider factors such as usage conditions and spark plug condition.

Q: What type of fuel should I use in my Kubota Z125S?

A: It is recommended to use unleaded gasoline with an octane rating of 87 or higher in the Kubota Z125S. Using ethanol-blended gasoline with a maximum of 10% ethanol (E10) is acceptable. Avoid using gasoline with higher ethanol content, as it can potentially damage the engine.

Q: Is it necessary to have a professional look at my Kubota Z125S if it won’t start?

A: While you can attempt basic troubleshooting steps yourself, if the problem persists or if you’re unsure about performing advanced repairs, it’s advisable to seek professional assistance. Kubota technicians or authorized dealers have the knowledge and expertise to diagnose and resolve complex starting issues.

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Dealing with a Kubota Z125S that won’t start can be frustrating, but with the right troubleshooting steps and maintenance practices, you can overcome this issue. Remember to check the fuel level, inspect the spark plug, clean or replace the fuel filter, test the battery, and verify the ignition switch. If the problem persists, seeking professional assistance is recommended. By following these guidelines and maintaining your Kubota Z125S, you can enjoy smooth and hassle-free mowing for years to come.

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