Kubota ZD21 aftermarket parts

Kubota ZD21 Parts and Parts Manual PDF

Kubota ZD21 Parts 

To help you with maintenance and repairs, it’s essential to have access to the Kubota ZD21 parts and parts manual in PDF format.

One of the key resources for any Kubota ZD21 owner is the parts manual, which provides detailed diagrams and lists of all the components that make up this powerful mower.

These diagrams are essential for identifying the specific parts you need for maintenance or repairs.

In the digital age, having a PDF version of your Kubota ZD21 parts manual is incredibly convenient. You can easily access it on your computer, tablet, or smartphone, allowing you to search for parts and information quickly and efficiently.

To obtain the Kubota ZD21 parts manual PDF, you can check the official Kubota website or trusted online sources that provide manuals for various equipment.

Kubota ZD21 Parts List

The parts list is an indispensable reference for any Kubota ZD21 owner. It provides a comprehensive inventory of all the parts available for your mower. Having a complete Kubota ZD21 parts list ensures that you can easily order the right components when needed, saving you time and frustration.

Kubota ZD21 Deck Parts

The deck of your Kubota ZD21 is a crucial component responsible for cutting your grass to perfection. Over time, deck parts may wear out or become damaged, affecting the mower’s performance. The parts manual and diagrams will help you identify and locate the Kubota ZD21 deck parts you need to keep your lawn looking its best.

  1. Mower Blades: These are the cutting blades that attach to the mower deck. Depending on the size and configuration of your deck, you may need one or more blades.
  2. Belt(s): Zero-turn mowers typically have one or more belts that drive the blades. There may be a deck drive belt and a PTO (Power Take Off) belt.
  3. Spindles: Spindles are components that house the mower blades and allow them to rotate. You may need to replace spindles if they become damaged or worn.
  4. Idler Pulleys: Idler pulleys help maintain tension on the belts. They can wear out over time and need replacement.
  5. Deck Shell: If the deck shell is damaged or rusted, you might need to replace it.
  6. Deck Wheels: These wheels support and guide the mower deck as it mows. They can wear out and require replacement.
  7. Deck Wash Kit: Some mower decks come with a deck wash kit that allows you to clean the underside of the deck easily.
  8. Deck Lift Components: The deck lift system includes levers, brackets, and other components that allow you to adjust the deck height. If these parts become damaged, they may need replacement.
  9. Deck Bearings: Bearings help the moving parts of the deck function smoothly. If you notice excessive noise or vibration, you might need to replace deck bearings.
  10. Anti-Scalp Rollers: These rollers prevent the deck from scalping the ground, especially when mowing over uneven terrain.
  11. Deck Wash Port: Some mower decks have a washout port for cleaning. If it’s damaged or clogged, you may need a replacement.

Kubota ZD21 Parts Cup Washers

Cup washers may seem like small and insignificant parts, but they play a vital role in securing various components of your Kubota ZD21. When searching for Kubota ZD21 parts cup washers, consult your parts manual and diagrams to ensure you choose the correct size and type for your mower.

Kubota ZD21 Front Wheel Parts

Maintaining the front wheels of your Kubota ZD21 is crucial for stability and manoeuverability. Whether you need replacement front wheel bearings or other front wheel parts, the parts manual and diagrams will guide you to the right components for a smooth and efficient ride.

The Kubota ZD21 is a zero-turn mower, and it typically doesn’t have front wheels like a traditional lawnmower. Instead, it has two large rear wheels and two hydrostatic transmission units that allow it to pivot and maneuver easily without the need for front wheels.

Kubota ZD21 Fuel Tank Parts and Diagram

The fuel tank is a critical component of your Kubota ZD21, and it’s essential to keep it in good condition. Should you encounter any issues with your fuel tank or need to replace specific parts, the parts manual and diagrams will provide the necessary guidance and information.

Kubota ZD21 Gearbox Parts

The gearbox is responsible for transferring power from the engine to the cutting blades. If you experience any problems with your Kubota ZD21’s gearbox, consult your parts manual and diagrams to identify the necessary gearbox parts for repair or replacement.

Kubota ZD21 Parts Oil Filters

Proper maintenance of your Kubota ZD21’s engine is crucial for its longevity and performance. Oil filters are essential for keeping the engine oil clean and free from contaminants. Ensure you have the correct Kubota ZD21 parts oil filters by referring to your parts manual and diagrams when performing oil filter replacements.

Kubota ZD21 Problems and Solutions

Like any piece of equipment, Kubota ZD21 mowers may encounter issues over time. Some common problems include engine-related issues, fuel pump malfunctions, and hydraulic fluid problems. To troubleshoot and address these problems effectively, consult your Kubota ZD21 parts manual and diagrams for guidance.

Kubota ZD21 Specs

Understanding the specifications of your Kubota ZD21 is essential for proper operation and maintenance. The parts manual typically includes detailed information about the mower’s specifications, such as engine size, cutting deck dimensions, and weight. Familiarizing yourself with these specifications will help you make informed decisions when purchasing parts and accessories.


  • Type: Diesel, liquid-cooled, 3-cylinder engine
  • Displacement: Approximately 719 cc (cubic centimeters)
  • Horsepower: Around 21 HP (horsepower)

2. Fuel System:

  • Fuel Type: Diesel fuel
  • Fuel Tank Capacity: Varies by model, but typically around 6 to 7 gallons (22.7 to 26.5 liters)

3. Transmission:

  • Hydrostatic transmission with twin HST pedals or levers for controlling speed and direction

4. Cutting Deck:

  • Cutting Width: Typically available in various deck widths ranging from 48 to 60 inches (122 to 152 centimeters)
  • Number of Blades: 3 blades
  • Cutting Height: Adjustable in multiple positions

5. Steering:

  • Zero-turn steering system for excellent manoeuvrability

6. Dimensions:

  • Overall Length: Varies depending on the specific model and configuration
  • Overall Width: Varies depending on the specific deck width
  • Weight: Varies depending on the model and accessories, but typically between 1,200 and 1,500 pounds (544 to 680 kilograms)

7. Tires:

  • Front Tires: Pneumatic tires
  • Rear Tires: Pneumatic tires

8. Features:

  • ROPS (Roll-Over Protective Structure) for operator safety
  • Comfortable operator seat
  • High-capacity mower deck
  • Easy-access maintenance points
  • Optional bagging and mulching attachments

9. Speed:

  • The speed of the Kubota ZD21 may vary depending on the model and terrain, but it can typically reach speeds of up to 10-12 mph (16-19 km/h).

Kubota ZD21 Fuel Pump

The fuel pump is a critical component of your Kubota ZD21, responsible for delivering fuel to the engine. If you suspect issues with your fuel pump, refer to your parts manual and diagrams to identify the correct Kubota ZD21 fuel pump replacement part and ensure your mower runs smoothly.

Kubota ZD21 Engine

The heart of your Kubota ZD21 is its engine. Regular maintenance and timely replacements of engine components are essential to keep it running efficiently. Your parts manual and diagrams will be your trusted resources for identifying and sourcing the right Kubota ZD21 engine parts when needed.

Kubota ZD21 Hydraulic Fluid

Maintaining the hydraulic system of your Kubota ZD21 is crucial for smooth operation and control. The parts manual and diagrams will help you identify the necessary parts and components related to the hydraulic system, ensuring it functions optimally.

To determine the appropriate hydraulic fluid for a Kubota ZD21 zero-turn mower, you can refer to the manufacturer’s recommendations, as well as insights from Kubota owners and experts. Here’s what the search results suggest:

  • Kubota ZD21-EC/ZD21N-EC (2002 and after): For these models, Kroon-Oil recommends using Super UDT2 Synthetic Universal Trans-Hydraulic Fluid
    This fluid is available in 1-quart containers with the item number 70000-40200
  • Transmission oil: One Kubota ZD21 owner mentions using thin Kubota oil for the transmission
    However, the specific type and viscosity of this oil are not provided in the search results.
  • Gearbox oil: Another Kubota owner mentions using 75w140 synthetic oil for their gearboxes
    This oil is not specifically recommended for the ZD21, but it may be suitable for other components of the mower.
  • Fluid and filter maintenance: According to LawnEQ Blog, the transmission oil filter cartridge should be changed after 50 hours and every 400 hours. Two filters are used, one for the hydraulic pump and the other for the transmission

What kind of gear lube is used for a Kubota ZD21 rear axle and transaxle

The Kubota ZD21 rear axle and transaxle require specific gear lube for optimal performance and protection. The recommended gear lube for the Kubota ZD21 is:

  • KUBOTA Super Universal Dynamic Tractor Fluid (SUPER UDT): This is the original and recommended transmission hydraulic fluid for Kubota equipment
    It is used for both lubricating the transmission and operating the hydraulic system. Using KUBOTA UDT or SUPER UDT fluid ensures proper operation of the hydraulic system and complete lubrication of the transmission, providing optimum protection and performance
  • Full synthetic gear oil: Some users have reported using full synthetic gear oil for their ZD21 gearbox oil
    While not specifically mentioned in the official Kubota documentation, full synthetic gear oil can provide excellent protection and performance for the rear axle and transaxle.
  • EP gear lubes: For conventional rear axles, limited-slip rear axles, and transmissions requiring EP (extreme pressure) gear lubes under high-speed, high-load, high-temperature, or severe operating conditions, EP gear lubes are recommended

How to take the deck off a Kubota ZD21

Before you begin, make sure the engine is off, and the parking brake is engaged. Always wear appropriate safety gear, such as gloves and safety glasses.

Tools You’ll Need:

  • Socket set or wrench set
  • Jack stands or blocks of wood


  1. Park the Mower: Park your Kubota ZD21 on a level surface.
  2. Lower the Mower Deck: Lower the mower deck to its lowest position using the height adjustment lever. This will help you access the components more easily.
  3. Disconnect the PTO Belt:
    • Locate the PTO (Power Take-Off) belt that connects the mower deck to the engine. It’s usually a belt running from the engine to a pulley on the mower deck.
    • To release tension on the belt, engage the PTO lever to the off/disengaged position. This will loosen the belt.
    • Carefully slide the belt off the PTO pulley on the engine. You may need to use a socket or wrench to remove any retaining bolts or clips securing the belt to the deck.
  4. Remove the Deck Hangers:
    • The mower deck is typically attached to the mower frame by hanger brackets or pins. These are located on each side of the deck.
    • Use a socket set or wrench to remove the bolts or pins securing the hanger brackets to the deck. Depending on your model, there may be one or more on each side.
  5. Disconnect the Front Linkage:
    • At the front of the mower deck, there may be a linkage system that connects it to the front of the mower frame.
    • Use a socket set or wrench to remove any bolts or pins securing the linkage to the deck.
  6. Slide the Deck Out:
    • Once all the connections are disconnected and any retaining bolts or pins are removed, you should be able to slide the mower deck out from under the mower.
  7. Raise and Secure the Deck: Use jack stands or blocks of wood to support the deck and keep it in an elevated position. This will make it easier to reattach the deck later.

Remember to take note of how everything is connected and the order in which you removed the components, as you’ll need to reverse these steps when reinstalling the deck.

When reattaching the deck, ensure that all the connections are secure, the PTO belt is properly tensioned, and the deck is level for optimal mowing performance.

Always consult your Kubota ZD21 operator’s manual for specific instructions and safety guidelines.

How to adjust drive leaver on a Kubota ZD21

The Kubota ZD21 is a zero-turn mower, and it typically doesn’t have a “drive lever” in the same way a traditional lawn tractor might. Instead, it uses two separate hydrostatic transmission controls to manoeuvre.
  1. Check for Obstructions: Ensure that there are no obstructions or debris blocking the movement of the mower’s drive wheels. Rocks, sticks, or other objects can hinder proper operation.
  2. Check the Drive Belt: Examine the drive belt that connects the engine to the transmission. If it’s worn, damaged, or loose, it may need to be replaced or tightened.
  3. Check the Hydrostatic Transmission Controls: The hydrostatic transmission on a zero-turn mower is typically controlled by two lap bars or handles. Make sure both controls are in the neutral position (usually outward) when you want the mower to remain stationary.
  4. Adjust the Lap Bars: If you find that the mower isn’t responding as expected or if it’s drifting when the lap bars are in the neutral position, you may need to adjust the lap bars. This can usually be done by loosening a few bolts on each lap bar and repositioning them so that they are truly in the neutral position when the bars are released.
  5. Check for Air in the Hydraulic System: If your mower uses a hydraulic drive system, it’s possible that air has entered the system, causing it to operate erratically. Bleeding the hydraulic system may be necessary. Consult your operator’s manual for instructions on how to do this properly.
  6. Consult the Operator’s Manual: Always consult the operator’s manual that came with your Kubota ZD21 for specific instructions on adjusting and troubleshooting the drive system. The manual will provide detailed information and diagrams related to your mower’s components and controls.
  7. Seek Professional Help: If you are unable to diagnose or fix the issue on your own, or if the issue is more complex than simple adjustments can solve, it’s advisable to contact a Kubota service technician or authorized dealer for assistance.

How to change the fuel filter on a Kubota ZD21

  1. Prepare the equipment: Park the mower on a level surface, engage the parking brake, and turn off the engine. Allow the engine to cool down before starting the maintenance.
  2. Locate the fuel filter: The fuel filter is typically located near the fuel tank or along the fuel line. Refer to your Kubota ZD21’s manual for the exact location.
  3. Turn off the fuel valve: If your mower is equipped with a fuel valve, turn it off to prevent fuel from flowing while you’re working on the filter.
  4. Release the pressure: To release any pressure in the fuel system, remove the fuel cap carefully. This step is essential for your safety.
  5. Prepare for fuel spillage: Place a container or a rag under the fuel filter to catch any fuel that may spill during the replacement process.
  6. Remove the old fuel filter: Use a wrench or pliers to loosen the clamps securing the fuel lines to the filter. Slide the clamps away from the filter, then carefully disconnect the fuel lines from the filter. Be prepared for some fuel spillage during this step.
  7. Install the new fuel filter: Install the new fuel filter by connecting the fuel lines to the appropriate ports on the filter. Ensure that the connections are secure and tight.
  8. Tighten the clamps: Slide the clamps back over the fuel lines and tighten them securely to prevent any fuel leaks.
  9. Turn on the fuel valve: If you turned off the fuel valve in step 3, turn it back on to allow fuel to flow through the system.
  10. Check for leaks: Start the engine and let it run for a few minutes while checking for any fuel leaks around the filter and fuel lines. If you notice any leaks, turn off the engine and tighten the connections further.
  11. Dispose of the old filter: Properly dispose of the old fuel filter according to your local regulations for hazardous waste.
  12. Clean up: Clean up any spilled fuel and ensure that the work area is free of any flammable materials before operating the mower again.

How to install front wheel bearings on a Kubota ZD21

To install front wheel bearings on a Kubota ZD21 zero-turn mower, you will need the following tools and materials:

  • Front wheel bearing rebuild kit (e.g., HD Switch Front Wheel Bearing Rebuild Kit)
  • Socket set
  • Wrench set
  • Jack or lift
  • Grease gun
  • Mallet or hammer

Here is a step-by-step guide to help you with the installation process:

  1. Prepare the mower: Park the mower on a flat and level surface. Engage the parking brake and turn off the engine. If necessary, raise the front of the mower using a jack or lift to provide easier access to the front wheels.
  2. Remove the front wheel: Use a socket set or wrench to remove the lug nuts securing the front wheel to the axle. Carefully slide the wheel off the axle and set it aside.
  3. Remove the old bearings: Depending on the specific model of your Kubota ZD21, the front wheel bearings may be sealed or unsealed. If they are sealed, you will need to use a mallet or hammer to tap out the old bearings from the wheel hub. If they are unsealed, you can simply remove them by hand.
  4. Clean the wheel hub: Before installing the new bearings, clean the wheel hub thoroughly to remove any dirt, debris, or old grease. You can use a rag or a small brush for this task.
  5. Apply grease to the new bearings: Take the new front wheel bearings from the rebuild kit and apply a generous amount of grease to them. This will help ensure smooth operation and longevity.
  6. Install the new bearings: Carefully insert the new bearings into the wheel hub, making sure they are properly seated. If the bearings are sealed, use a mallet or hammer to tap them into place. If they are unsealed, you can press them in by hand.
  7. Reinstall the front wheel: Slide the front wheel back onto the axle and secure it with the lug nuts. Tighten the lug nuts using a socket set or wrench, but do not overtighten them.
  8. Repeat the process for the other front wheel: Follow the same steps to install the front wheel bearings on the other side of the mower.
  9. Lower the mower: If you used a jack or lift to raise the front of the mower, carefully lower it back down to the ground.
  10. Test the front wheels: Start the engine and engage the mower’s controls to ensure that the front wheels are rotating smoothly and without any wobbling or noise. If you notice any issues, double-check the installation of the front wheel bearings and make any necessary adjustments.

How to change the mower belt on a Kubota ZD21

  1. Prepare the mower: Park the mower on a flat surface, engage the parking brake, and turn off the engine. Disconnect the spark plug wire to prevent accidental starting.
  2. Lower the mower deck: Lower the mower deck to its lowest position using the deck height adjustment lever.
  3. Remove the mower deck: Depending on the model, you may need to remove the mower deck to access the belt. Consult your owner’s manual or the specific instructions for your model. In some cases, you may be able to access the belt without removing the deck
  4. Release the tension on the belt: Locate the tensioner pulley, which is responsible for keeping the belt tight. Use a wrench or socket to rotate the tensioner pulley and release the tension on the belt. This will allow you to remove the old belt
  5. Remove the old belt: Carefully slide the old belt off the pulleys, making note of its routing for the installation of the new belt.
  6. Install the new belt: Route the new belt around the pulleys, following the same path as the old belt. Make sure the inside of the belt (V side) is in contact with the pulleys, and the outside of the belt (flat side) is against any idlers
  7. Tension the new belt: Rotate the tensioner pulley again to create tension on the new belt. Check the tension by pressing on the belt with your finger. It should have a slight give but not be too loose or too tight
  8. Reinstall the mower deck: If you had to remove the mower deck, now is the time to reinstall it. Follow the reverse steps of the deck removal process, ensuring all connections are secure.
  9. Test the new belt: Start the mower and engage the blades to test the new belt. Observe the belt’s operation and listen for any unusual noises. If everything is working correctly, you have successfully changed the mower belt on your Kubota ZD21.

How to change a radiator on a Kubota ZD21

Changing the radiator on a Kubota ZD21 or any other similar tractor or mower involves a series of steps. Please note that the specific steps and procedures may vary slightly depending on the exact model and year of your Kubota ZD21, so refer to your owner’s manual for model-specific instructions. Here is a general guide to replacing the radiator:

Tools and materials you will need:

  • New radiator
  • Coolant (antifreeze)
  • Socket wrench set
  • Screwdrivers
  • Pliers
  • Drain pan
  • Hose clamps
  • Hose cutter (if necessary)
  • Safety goggles
  • Gloves

Safety Precautions:

  1. Ensure the engine is cool before you start any work on the cooling system.
  2. Disconnect the battery to prevent accidental starting.


  1. Drain the Coolant:
    • Position a drain pan beneath the radiator to catch the coolant.
    • Locate the radiator drain plug, typically at the bottom of the radiator. Loosen it with a wrench and allow the coolant to drain into the pan.
    • Dispose of the old coolant properly according to your local regulations.
  2. Remove the Radiator Shroud:
    • Depending on your ZD21 model, you may have a shroud or fan cover over the radiator. Remove it by loosening the bolts or clips.
  3. Disconnect Hoses:
    • Identify the hoses connected to the radiator. There should be at least two hoses – an inlet and an outlet hose.
    • Use pliers to loosen and remove the hose clamps securing the hoses to the radiator.
    • Carefully pull the hoses off the radiator fittings. If they are stuck, you may need to gently twist or use a screwdriver to help detach them.
  4. Remove the Radiator:
    • Locate and remove the bolts or brackets that secure the radiator to the tractor. These are typically found on the top and bottom of the radiator.
    • Lift the radiator out of its mounting.
  5. Install the New Radiator:
    • Place the new radiator in the same position as the old one.
    • Reattach the mounting brackets or bolts to secure the radiator in place.
  6. Reconnect Hoses:
    • Reattach the hoses to the new radiator fittings and secure them with hose clamps.
  7. Refill with Coolant:
    • Mix a 50/50 solution of coolant and water (unless you’re using pre-mixed coolant).
    • Slowly pour the coolant into the radiator until it reaches the appropriate level. You may need to “burp” the system to remove air bubbles.
    • Reinstall the radiator cap.
  8. Test for Leaks:
    • Start the engine and allow it to run for a few minutes. Check for any coolant leaks around the radiator and hoses.
  9. Reattach the Radiator Shroud:
    • If you removed a shroud or fan cover, reattach it and secure it in place.
  10. Top Off Coolant:
    • Check the coolant level in the radiator and top it off as needed.
  11. Reconnect the Battery:
    • Reconnect the tractor’s battery.
  12. Dispose of Old Parts:
    • Properly dispose of the old radiator and any other parts you replaced.