Kubota D850 Parts and Parts Manual PDF

Kubota D850 Parts

The Kubota D850 is a diesel-powered utility tractor that is known for its versatility, power, and durability. It is a popular choice for a variety of tasks, including landscaping, agriculture, and construction.

The D850 is powered by a 34.3 horsepower (25.2 kW) Kubota ETVCS diesel engine that meets Tier 4 Final emission standards. It has a hydrostatic transmission with cruise control, making it easy to operate. The D850 also features four-wheel drive and a rear differential lock for improved traction in tough conditions.

The D850 has a lift capacity of 2,200 pounds (1,000 kg) and a three-point hitch, making it ideal for attaching implements such as mowers, tillers, and snow blowers. It also has a PTO (power take-off) for powering implements such as generators and wood chippers.

Kubota D850 Specs


  1. Displacement: The D850 has a displacement of approximately 0.898 liters (or 898 cubic centimeters).
  2. Power Output: The power output of the D850 engine can vary depending on its application and the specific model it’s installed in. Typically, it can produce around 15-20 horsepower (hp) at its peak performance.
  3. Fuel System: The engine employs a direct injection fuel system, which helps optimize fuel efficiency and performance.
  4. Cooling System: It features a liquid-cooling system to maintain optimal operating temperatures, ensuring efficient performance and longevity of the engine.
  5. Aspiration: The D850 engine typically uses a natural aspiration method, meaning it doesn’t employ a turbocharger or supercharger to force air into the cylinders.
  6. Cylinder Configuration: It has three cylinders arranged in-line, which helps in achieving smooth operation and balanced power delivery.
  7. Compression Ratio: The compression ratio of the D850 engine is usually in the range of 19:1 to 20:1, which is common for diesel engines and contributes to their efficiency.
  8. Dimensions and Weight: The engine is compact and lightweight, making it suitable for various applications where space and weight are considerations.
  9. Emissions: Depending on the model and year of manufacture, the D850 engine may comply with different emissions standards, such as Tier 4 Final or earlier versions, in accordance with regulatory requirements.

Kubota D850 Thermostat

The Kubota D850 tractor uses a thermostat to regulate the engine coolant temperature, ensuring optimal performance and preventing overheating. Here’s what you need to know about the Kubota D850 thermostat:


  • The thermostat is a valve that opens and closes based on engine temperature. When the engine is cold, the thermostat remains closed, allowing coolant to circulate only within the engine block, facilitating faster warm-up.
  • This regulated flow of coolant ensures the engine maintains a consistent operating temperature, preventing overheating and engine damage.


  • The thermostat housing is typically located on the cylinder head or engine block, near the water inlet pipe from the radiator.


  • If the thermostat malfunctions or fails to maintain the proper engine temperature, it needs to be replaced. Symptoms of a faulty thermostat include engine overheating, inconsistent engine temperature, or the engine taking too long to warm up.
  • It’s recommended to consult your Kubota D850 service manual or a qualified mechanic for specific instructions on locating, testing, and replacing the thermostat.

Additional Tips:

  • Use genuine Kubota parts or high-quality aftermarket parts that meet the manufacturer’s specifications.
  • Check your coolant level regularly and ensure it’s always at the recommended level.
  • Flush the cooling system periodically to remove any debris or rust that could clog the thermostat housing or radiator.
  • Regularly monitor your engine temperature gauge to identify any potential issues with the thermostat or cooling system.

Kubota D850 Engine Parts Manual


  1. Introduction: This section provides an overview of the manual, including its purpose, intended audience, and instructions on how to use it effectively.
  2. Engine Diagrams: Diagrams illustrating the layout of the engine and its various components can be found in this section. These diagrams help users identify parts and understand their locations within the engine.
  3. Parts Catalog: The parts catalog section lists all the individual components and parts that make up the Kubota D850 engine. Each part is usually accompanied by a part number, description, and quantity required.
  4. Exploded Views: Exploded views provide detailed illustrations of the engine components, showing how they are assembled and disassembled. This section is helpful for understanding the relationship between different parts and how they fit together.
  5. Part Number Index: This section contains an alphabetical index of part numbers, making it easy to quickly locate specific parts within the manual.
  6. Part Descriptions and Specifications: Detailed descriptions and specifications for each part are provided in this section. This may include dimensions, materials, tolerances, and other relevant information.
  7. Cross-References: Cross-references may be included to help users find compatible parts or alternative part numbers if a specific part is unavailable.
  8. Maintenance and Service Information: Some parts manuals include maintenance and service information for engine components, such as recommended service intervals, inspection procedures, and troubleshooting tips.
  9. Warranty Information: Warranty information may be included, detailing the warranty coverage for genuine Kubota parts and any terms or conditions that apply.
  10. Ordering Information: This section provides instructions on how to order parts, including contact information for Kubota dealers or authorized parts distributors.
  11. Safety Precautions: Safety precautions relevant to handling engine parts, such as wearing protective gear or using lifting equipment, may be included to ensure safe handling practices.
  12. Appendices: Appendices may contain additional reference materials, such as conversion tables, torque specifications, or other useful information related to engine parts.

Kubota D850 Oil Capacity

These are some general ranges of oil capacity for Kubota D850 engines based on year and variant, but remember to verify the exact amount for your specific engine:

  • Earlier D850 models (e.g., pre-2009): 2.8 to 3.1 liters (3.0 to 3.3 quarts)
  • Later D850 models (e.g., 2009 and later): 3.0 to 3.2 liters (3.2 to 3.4 quarts)

Kubota D850 Rebuild Kit

A rebuild kit for the Kubota D850 engine typically includes a comprehensive set of components necessary for overhauling or rebuilding the engine. These kits are commonly used when the engine has reached the end of its service life, experienced significant wear, or encountered damage. This is what is normally in a rebuild kit for the Kubota D850:

  1. Pistons and Piston Rings: Essential for sealing the combustion chamber and transferring energy from the expanding gases to the crankshaft. Piston rings help maintain compression and control oil consumption.
  2. Cylinder Liners or Sleeves: Cylindrical inserts in the engine block that provide a smooth surface for the piston to move and help dissipate heat.
  3. Main Bearings and Rod Bearings: Main bearings support the crankshaft within the engine block, while rod bearings support the connecting rods on the crankshaft. These bearings reduce friction and ensure smooth operation.
  4. Gasket Set: A complete gasket set typically includes all the gaskets, seals, and o-rings needed to reseal the engine during reassembly. This includes head gaskets, valve cover gaskets, oil seals, and various other seals required for the engine’s components.
  5. Piston Pins and Retainers: Piston pins (wrist pins) connect the pistons to the connecting rods. They may be included in the rebuild kit along with retaining clips or other hardware.
  6. Connecting Rod Bushings: These bushings are installed in the small end of the connecting rods and provide a smooth surface for the piston pins to rotate.
  7. Timing Components: Timing components such as timing belts, timing chains, tensioners, and guides may be included if the engine has a timing belt or chain that needs replacement during the rebuild process.
  8. Engine Bearings and Thrust Washers: Depending on the engine design, the rebuild kit may include additional bearings and thrust washers for other components such as the camshaft or balance shafts.
  9. Optional Components: Depending on the supplier and the specific needs of the rebuild, other components such as valve guides, valve stem seals, camshaft bushings, or piston pin bushings may be included.

Kubota D850 Timing Cover Gasket

The timing cover gasket for the Kubota D850 engine is a critical component that seals the timing cover to the engine block. It helps prevent oil leaks and ensures proper lubrication of the timing components. When replacing the timing cover gasket, it’s essential to use a high-quality gasket made from durable materials to ensure a proper seal and reliable performance.

While specific part numbers and availability may vary depending on your location and supplier, you can typically find timing cover gaskets for the Kubota D850 engine from Kubota dealers, authorized parts distributors, or aftermarket suppliers specializing in engine gaskets and seals.

When purchasing a timing cover gasket for the Kubota D850 engine, consider the following:

  1. Compatibility: Ensure that the timing cover gasket is compatible with your Kubota D850 engine model and year of manufacture. Gaskets may vary depending on engine variations and configurations.
  2. Quality: Choose a high-quality gasket made from durable materials that can withstand the temperature and pressure conditions within the engine. OEM (Original Equipment Manufacturer) gaskets or aftermarket gaskets from reputable suppliers are recommended for reliable performance.
  3. Sealant Compatibility: Some timing cover gaskets may require the use of sealant or gasket maker in specific areas to ensure a proper seal. Follow the manufacturer’s recommendations regarding sealant application and compatibility.
  4. Installation: Proper installation is crucial for ensuring a leak-free seal and reliable performance. Clean the mating surfaces thoroughly, apply sealant if required, and torque the fasteners to the manufacturer’s specifications.
  5. Warranty: Check if the timing cover gasket comes with any warranty coverage from the manufacturer or supplier. This can provide peace of mind regarding the quality and reliability of the gasket.

Kubota D850 Temperature Sensor

The Kubota D850 engine utilizes various temperature sensors to monitor critical engine functions and maintain optimal operating temperature.

Types of Temperature Sensors:

  • Coolant Temperature Sensor (CTS): Monitors the coolant temperature and sends data to the Engine Control Unit (ECU) for adjustments to fuel injection, fan speed, etc.
  • Oil Temperature Sensor (OTS): Monitors the engine oil temperature and alerts the ECU of potential overheating issues.
  • Intake Air Temperature Sensor (IATS): Measures the incoming air temperature, impacting fuel injection and engine performance.


  • Typically, the Coolant Temperature Sensor is located near the thermostat housing on the cylinder head or engine block.
  • The Oil Temperature Sensor might be located near the oil filter or on the engine block.
  • The Intake Air Temperature Sensor is usually positioned in the air intake manifold.

Troubleshooting and Replacement:

  • Symptoms of faulty temperature sensors can include engine overheating, erratic engine performance, or warning lights on the dashboard.
  • Replacing temperature sensors often requires specific tools and knowledge due to their location and connection to the engine’s electrical system. Consult your service manual or seek professional help for accurate diagnosis and repair.

Important Recommendations:

  • Identify your specific Kubota D850 model and year: Different models might have varying sensor types and locations. Refer to your service manual or consult your Kubota dealer for precise information.
  • Use genuine Kubota parts or high-quality aftermarket parts: Ensure compatibility with your engine model and specifications.
  • Follow repair procedures carefully: Consult your service manual or seek professional assistance to avoid causing further damage.

Kubota D850 Water Flange

The water flange on the Kubota D850 engine is a component that connects the engine’s cooling system to the radiator and other cooling system components. It typically serves as an interface for coolant hoses and may include ports for sensors or temperature switches.

  1. Location: The water flange is usually located on the engine block or cylinder head, near the front of the engine. It’s positioned to facilitate the flow of coolant between the engine and the radiator.
  2. Material: Water flanges are commonly made from durable materials such as aluminum or cast iron to withstand the temperature and pressure variations experienced in the cooling system.
  3. Ports: The water flange may feature ports or fittings for coolant hoses, allowing coolant to flow into and out of the engine. It may also have ports for sensors or temperature switches that monitor coolant temperature and control the engine’s cooling system.
  4. Sealing Surface: The water flange has a sealing surface that mates with a gasket to prevent coolant leaks. It’s essential to ensure that the sealing surface is clean and free of debris when installing a new water flange or replacing a gasket.
  5. Compatibility: When purchasing a water flange for the Kubota D850 engine, ensure that it is compatible with your specific engine model and any modifications or variations it may have. It should match the mounting points and coolant hose connections of your engine.
  6. Installation: Proper installation of the water flange is crucial for preventing coolant leaks and ensuring efficient engine cooling. Follow the manufacturer’s recommendations and torque specifications when installing the water flange and associated components.
  7. Maintenance: Inspect the water flange regularly for signs of coolant leaks, corrosion, or damage. Replace the water flange or associated gaskets if any issues are detected to prevent coolant loss and potential engine overheating.

Kubota D850 Alternator

The alternator in the Kubota D850 engine is a crucial component of the electrical system, responsible for generating electrical power to charge the battery and power the electrical accessories while the engine is running.

  1. Location: The alternator is typically mounted on the engine block and is driven by a belt connected to the crankshaft pulley. Its location may vary depending on the equipment application and mounting configuration.
  2. Function: The alternator converts mechanical energy from the engine’s rotation into electrical energy. It produces alternating current (AC), which is then converted to direct current (DC) by the vehicle’s electrical system to power lights, ignition, accessories, and recharge the battery.
  3. Output: The output rating of the alternator determines its capacity to supply electrical power. Depending on the model and specifications, the alternator in the Kubota D850 engine may have different output ratings, typically ranging from around 25 to 45 amps.
  4. Voltage Regulation: The alternator includes a voltage regulator that controls the output voltage to maintain a consistent voltage level within the electrical system. This ensures proper charging of the battery and prevents overcharging or undercharging of electrical components.
  5. Wiring Connections: The alternator is connected to the electrical system via wiring harnesses, which transmit electrical power to and from the alternator. These connections must be secure and free of corrosion to ensure proper electrical conductivity.
  6. Maintenance: Regular maintenance of the alternator is essential for optimal performance and longevity. This may include inspecting the belt for wear and proper tension, checking electrical connections for tightness and corrosion, and testing the output voltage and current of the alternator.
  7. Replacement: If the alternator fails or malfunctions, it may need to be replaced. When replacing the alternator in the Kubota D850 engine, it’s essential to choose a compatible replacement part that matches the output rating and mounting configuration of the original alternator.
  8. OEM vs. Aftermarket: Alternators are available from OEM (Original Equipment Manufacturer) sources like Kubota, as well as from aftermarket suppliers. Both OEM and aftermarket alternators can be suitable replacements, but it’s essential to choose a high-quality part from a reputable supplier to ensure reliability and compatibility.

Kubota D850 Starter

The starter motor in the Kubota D850 engine is a crucial component of the starting system, responsible for turning the engine over to initiate the combustion process.

  1. Location: The starter motor is typically mounted on the engine block, usually near the bottom or side of the engine. Its location may vary depending on the equipment application and mounting configuration.
  2. Function: The starter motor is engaged when the ignition switch is turned to the start position. It uses electrical power from the battery to turn the engine’s flywheel or flexplate, which rotates the engine’s crankshaft and initiates the combustion process.
  3. Starter Solenoid: The starter motor is often accompanied by a starter solenoid, which serves as a relay between the battery and the starter motor. The solenoid is engaged when the ignition switch is turned to the start position, allowing electrical current to flow from the battery to the starter motor.
  4. Drive Mechanism: The starter motor incorporates a drive mechanism, such as a pinion gear or Bendix drive, that meshes with the engine’s flywheel or flexplate. This allows the starter motor to transfer torque to the engine and initiate engine rotation.
  5. Voltage and Current Rating: The starter motor is designed to handle high currents and voltages to provide sufficient torque to turn the engine over. The voltage and current rating of the starter motor should match the specifications of the Kubota D850 engine and the vehicle’s electrical system.
  6. Maintenance: Regular maintenance of the starter motor is essential for optimal performance and longevity. This may include inspecting electrical connections for tightness and corrosion, testing the starter motor’s operation, and ensuring proper engagement with the flywheel or flexplate.
  7. Replacement: If the starter motor fails or malfunctions, it may need to be replaced. When replacing the starter motor in the Kubota D850 engine, it’s essential to choose a compatible replacement part that matches the voltage and current rating and mounting configuration of the original starter motor.
  8. OEM vs. Aftermarket: Starter motors are available from OEM (Original Equipment Manufacturer) sources like Kubota, as well as from aftermarket suppliers. Both OEM and aftermarket starter motors can be suitable replacements, but it’s essential to choose a high-quality part from a reputable supplier to ensure reliability and compatibility.

Kubota D850 Problems

Here are some common problems reported with the Kubota D850 engine:

  1. Starting Problems: Starting problems can be caused by issues with the fuel system, such as air in the fuel lines, clogged fuel filters, or problems with the fuel injectors. Electrical issues, such as a weak battery, faulty starter motor, or problems with the ignition system, can also contribute to starting problems.
  2. Overheating: Overheating can occur due to various reasons such as coolant leaks, a malfunctioning thermostat, clogged radiator, or insufficient coolant levels. It’s essential to address overheating issues promptly to prevent engine damage.
  3. Low Power or Performance: Low power or decreased engine performance can result from issues such as fuel system problems, worn or damaged engine components (e.g., piston rings, valves, or bearings), or improper engine timing.
  4. Excessive Smoke: Excessive smoke from the exhaust can indicate various problems, including worn piston rings, damaged valves or valve seals, over-fueling, or incomplete combustion due to issues with the fuel injection system.
  5. Oil Leaks: Oil leaks can occur from various engine components, including gaskets, seals, or worn piston rings. It’s essential to identify and repair oil leaks promptly to prevent loss of lubrication and potential engine damage.
  6. Coolant Leaks: Coolant leaks can occur from the radiator, hoses, water pump, or cylinder head gasket. Coolant leaks should be addressed promptly to prevent engine overheating and potential damage to internal components.
  7. Excessive Vibration or Noise: Excessive vibration or unusual noises from the engine can indicate problems such as worn bearings, misaligned components, or internal engine damage.
  8. Fuel Contamination: Fuel contamination, such as water or debris in the fuel system, can lead to engine performance issues, including rough idling, misfiring, or stalling.
  9. Electrical Problems: Electrical issues, such as faulty sensors, wiring problems, or a malfunctioning ECU (Engine Control Unit), can cause various engine performance issues and should be diagnosed and repaired by a qualified technician.