5 Most Common Kubota ZD21 Problems and Effective Fixes

The Kubota ZD21 is a great choice for most of your lawn maintenance needs however sometimes it can become frustrating when this great riding lawn mower isn’t running at full capacity. That’s why this article is here, to identify the most common problems that you may encounter with your Kubota ZD21. In this article we will go over what the Kubota ZD21 is, the common problems you may experience and how to fix them.

Table of Contents

What Is The Kubota ZD21?

The Kubota ZD21 is a zero-turn commercial riding lawn mower that was manufactured by Kubota. It is powered by a 21-horsepower diesel engine and is equipped with a 60-inch mower deck. The Kubota ZD21 was designed for commercial use but can also be used for residential purposes. It is known for its durability, ease of use and efficiency.

Kubota ZD21 Problems

1. Engine Won’t Start Problem

One of the most prominent problems that you may experience with your Kubota ZD21 is the engine not starting. There are several reasons why this may occur like;

  • A dead battery
  • A faulty/ damaged starter motor
  • A clogged fuel filter

Troubleshooting The Engine Not Starting Problem

  • If you have a dead or corroded battery then you have to replace it immediately in order to get the riding lawn mower working properly again.
  • You may also have to replace the starter motor if it is faulty or damaged in any way.
  • Be sure to regularly check the fuel filter and to clean it. If it is dirty or clogged, make sure to replace it right after.

2. Poor Performance Problems

This can mean that your Kubota ZD21 riding lawn mower is not producing enough power overall. This can manifest in ways like;

  • Decreased power and speed
  • Uneven cutting
  • Poor fuel efficiency

Troubleshooting Poor Performance Problems

  • Over time the air filter can become clogged thus preventing air from reaching the engine. To fix this problem you will need to replace the air filter.
  • The blades are responsible for cutting the grass, and if they are dull or damaged they won’t be able to cut the grass evenly. Therefore you will have to sharpen or replace the blades.
  • Lastly low tire pressure can also cause poor performance. If the tires are underinflated they won’t be able to provide enough traction which can result in decreased power and speed. Be sure to inflate the Kubota ZD21’s tires to the recommended pressure level.

3. Hydraulic System Failure

The hydraulic system is responsible for powering the mower deck and steering system. If the hydraulic system fails then you won’t be able to steer the mower or operate the mower deck. Failure to the hydraulic system is usually because of;

  • Low hydraulic fluid levels
  • Damaged hydraulic hoses
  • Leaks

Troubleshooting Hydraulic System Failure

  • The hydraulic fluid is responsible for lubricating the hydraulic system and providing the necessary pressure to operate the mower deck and steering system. Therefore you will need to add hydraulic fluid to the system.
  • Check or inspect the Kubota ZD21’s hydraulic system for any hydraulic system leaks and patch or replace any parts if you are able to do so.
  • Do not hesitate to seek the help of a professional Kubota mechanic if you are not confident in doing any of the fixes yourself.

4. Electrical Issues

The electrical system of your Kubota ZD21 riding lawnmower is responsible for powering all of the electrical components of the riding lawn mower. These issues can show up in several ways like;

  • The engine not starting
  • The headlights not working
  • The battery not charging

Troubleshooting Electrical Issues

The alternator is responsible for charging the battery and providing power to the electrical system. If the alternator is not working correctly then it won’t be able to charge the battery or provide power to the electrical system.

  • Check to see that the alternator is working correctly, you can do this by using a voltmeter, to make sure that current is flowing in and out of it.
  • You will also need to check and replace any damaged battery cable if it is necessary to do so, as electrical issues may also be caused by this.
  • Also make sure that any blown fuses are replaced to restore correct functionality to the riding lawn mower’s electrical system.

5. Transmission Problems

Transmission problems can also occur with your Kubota ZD21. This can manifest in ways like;

  • A difficulty in shifting gears
  • Grinding noises
  • Decreased power output

Troubleshooting Transmission Problems

If the transmission fluid levels are low then the transmission won’t be able to operate correctly.

  • Check the transmission fluid levels, if they are low then you will need to add transmission fluid to the system.
  • The transmission belt is responsible for transferring power from the engine to the transmission. If the belt is damaged it won’t be able to transfer power correctly causing transmission problems like noises and decreased power output to occur. You will need to replace the damaged transmission belt.

How To Prevent Problems With The Kubota ZD21

  • Check the oil levels regularly and change the oil and oil filter as needed.
  • Check the tire pressure regularly and inflate the tires to the recommended pressure.
  • Sharpen or replace the mower blades when they have become dull and worn out.
  • Check the battery and electrical system regularly and replace any damaged components.
  • Check the transmission fluid levels regularly and add transmission fluid when necessary.
  • Be sure to inspect the hydraulic hoses regularly and replace any damaged hoses as needed.

What Is The Kubota ZD21’s Horsepower And How Does It Compare To The Massey Ferguson 175?

The Kubota ZD21 is equipped with a three-cylinder liquid-cooled diesel engine that delivers up to 21 horsepower. This zero-turn riding lawn mower is designed to tackle large and tough mowing jobs with ease making it a popular choice among professional landscapers and homeowners alike. In comparison the Massey Ferguson 175 is a tractor that typically has a horsepower output ranging from 58-67 depending on the model. While both machines are designed for agricultural and lawn care purposes the Kubota ZD21’s compact size and maneuverability make it a great choice for those with smaller properties.

What Type Of Cutting Deck Does The Kubota ZD21 Have And What Are Its Capabilities?

The Kubota ZD21 is equipped with a 60-inch cutting deck that is designed for precision. This machine is capable of cutting grass at varying heights making it ideal for those who want a perfectly cut lawn. It also features a hydraulic deck lift that allows for easy and convenient adjustments to the cutting height. The cutting deck is made of durable materials that can withstand the wear and tear of regular use making it a long-lasting investment for your lawn care business or personal use.


The Kubota ZD21 is an excellent commercial riding lawn mower. However like any machine it will inevitably experience problems over the course of time. But by following the troubleshooting methods in this artivle then you can identify and fix the most common problems that you may encounter with your Kubota ZD21 riding lawn mower. Also remember to perform regular maintenance on your riding lawn mower to prevent these problems from occurring in the first place.