Overview
The Kubota ZD18F, ZD21F, ZD25F and ZD28F Mower Workshop Service Manual provides technical documentation for maintenance, troubleshooting, inspection and component repair of these Kubota riding mowers. The workshop reference covers diesel engine systems, hydrostatic transmission (HST), transaxle, front axle, hydraulic lift equipment, electrical systems and rotary mower assemblies. Its technical sections provide component construction, operating principles, servicing specifications, checking, adjustment, disassembly and repair procedures for the covered equipment.
The documentation includes separate engine service specifications for D722-E-XFM5, D782-E-XFM5 and D1105-E-ZD configurations, together with lubrication, cooling and fuel-system servicing. The transaxle chapter addresses hydrostatic pump and motor operation, check valves, high-pressure relief, oil flow, final reduction gears and power take-off (PTO) components. Additional chapters cover hydraulic control valves, lift cylinders, mower linkage, electrical starting and charging systems, and rotary mower power transmission. General information provides maintenance schedules, lubricants, tightening torques and special service tools.
Notice: The Engine chapter distinguishes separate servicing specification groups for the D722-E-XFM5 and D782-E-XFM5 engines and the D1105-E-ZD engine. Confirm the installed engine identification before applying component measurements or repair specifications. The supplied chapter index does not independently establish which engine is fitted to each covered mower configuration.
Table of Contents
Kubota ZD18F, ZD21F, ZD25F, ZD28F Manual
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01. Information, Safety and Specifications
- Safety First and Workshop Safety Instructions
- Mower Safety Decals and Warning Labels
- Machine Technical Specifications
- Machine Dimensions
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02. General Information and Maintenance
- Machine Identification
- General Workshop Precautions
- Electrical Wiring and Component Handling Precautions
- Battery, Fuse and Electrical Connector Handling
- Circuit Tester Precautions
- Lubricants, Fuel and Coolant Requirements
- General Fastener Tightening Torques
- Metric Screw, Bolt and Nut Specifications
- UNC and UNF Threaded Fastener Specifications
- Machine Maintenance Checklist
- Daily Inspection and Maintenance
- Initial 50-Hour Maintenance
- Initial 100-Hour Maintenance
- Initial 200-Hour Maintenance
- Periodic Maintenance — Every 50 Hours
- Periodic Maintenance — Every 100 Hours
- Periodic Maintenance — Every 150 Hours
- Periodic Maintenance — Every 200 Hours
- Periodic Maintenance — Every 400 Hours
- Annual Maintenance Requirements
- Two-Year Maintenance Requirements
- Additional Maintenance and Service Checks
- Special Service Tools for Engine Repair
- Special Service Tools for Machine Components
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03. Engine — Inspection and Servicing
- Engine Troubleshooting
- Engine Body Specifications — D722-E-XFM5 and D782-E-XFM5
- Lubricating System Specifications — D722-E-XFM5 and D782-E-XFM5
- Cooling System Specifications — D722-E-XFM5 and D782-E-XFM5
- Fuel System Specifications — D722-E-XFM5 and D782-E-XFM5
- Engine Body Specifications — D1105-E-ZD
- Lubricating System Specifications — D1105-E-ZD
- Cooling System Specifications — D1105-E-ZD
- Fuel System Specifications — D1105-E-ZD
- Engine Tightening Torque Specifications
- Engine Separation and Removal
- Engine Body Checking and Adjustment
- Engine Body Disassembly and Assembly
- Engine Body Inspection and Servicing
- Engine Lubricating System Checking
- Lubricating System Component Servicing
- Engine Cooling System Checking and Adjustment
- Cooling System Disassembly and Assembly
- Engine Fuel System Checking and Adjustment
- Fuel System Disassembly and Assembly
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04. Transaxle and Hydrostatic Transmission
- Transaxle Construction and Structure
- Travelling System Mechanism
- Hydrostatic Transmission (HST) Construction
- Hydrostatic Pump and Motor
- HST Check Valve
- HST Check and High-Pressure Relief Valve
- Hydrostatic Transmission Oil Flow
- Power Train Operating Principles
- Hydrostatic Transmission Control Linkage
- Final Reduction Gear Section
- Power Take-Off (PTO) System
- Transaxle Troubleshooting
- Transaxle Servicing Specifications
- Transaxle Tightening Torques
- Transaxle Checking and Adjustment
- Transaxle Separation and Removal
- Transaxle Disassembly and Assembly
- Hydrostatic Transmission Inspection and Servicing
- Transmission Case Inspection and Servicing
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05. Front Axle — Inspection and Servicing
- Front Axle Construction
- Front Axle Troubleshooting
- Front Axle Servicing Specifications
- Front Axle Tightening Torques
- Front Axle Checking and Adjustment
- Front Wheel and Wheel Bracket Separation
- Front Axle Disassembly and Assembly
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06. Hydraulic System and Mower Lift Linkage
- Hydraulic System Circuit Diagram
- Hydraulic Pump Construction
- Hydraulic Control Valve and Valve Adaptor
- Hydraulic Lift Cylinder
- Mower Lift Linkage Mechanism
- Hydraulic System Troubleshooting
- Hydraulic Servicing Specifications
- Hydraulic Control Valve Checking and Adjustment
- Hydraulic Pump Checking and Adjustment
- Hydraulic Cylinder Checking and Adjustment
- Hydraulic Control Valve, Pump and Cylinder Disassembly
- Hydraulic Control Valve, Pump and Cylinder Assembly
- Lift Cylinder Disassembly and Assembly
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07. Electrical System and Diagnostics
- Mower Electrical Wiring Diagram
- Engine Starting System
- Starter Motor
- Engine Glow Plug
- Starting Safety Switch and Limit Switch
- Electric Fuel Pump
- Engine Stop Solenoid
- Battery Charging System
- AC Dynamo
- Voltage Regulator
- Easy Checker Monitoring System
- Fuel Quantity Gauge
- Coolant Temperature Gauge
- Electrical System Troubleshooting
- Electrical Servicing Specifications
- Electrical Tightening Torques
- Battery Inspection and Testing
- Starting System Checking
- Starting System Disassembly and Assembly
- Starting System Component Servicing
- Charging System Inspection
- Charging System Disassembly and Assembly
- Charging System Component Servicing
- Lighting System Checking
- Electrical Gauge Inspection
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08. Rotary Mower — Mechanism and Servicing
- Rotary Mower Power Transmission
- Mower Lifting Mechanism
- Rotary Mower Troubleshooting
- Mower Servicing Specifications
- Mower Tightening Torques
- Mower Checking and Adjustment
- Rotary Mower Disassembly and Assembly
HST Relief-Valve Inspection and Mower Lift System Diagnosis
The Transaxle chapter documents the hydrostatic transmission’s pump and motor, check valve, high-pressure relief valve, oil flow and control linkage. These references are relevant when investigating irregular travelling performance or hydrostatic drive problems. The final reduction gear and PTO sections provide additional drivetrain information, allowing a technician to distinguish transmission-related symptoms from faults involving power delivery to the mower. Use the corresponding servicing specifications and checking procedures before dismantling the affected assembly.
The Hydraulic System chapter separately covers the hydraulic pump, control valve, lift cylinder and mower linkage, while the Rotary Mower chapter addresses cutting-drive power transmission and the lifting mechanism. When a mower fails to lift or operate correctly, these sections should be consulted according to the affected function rather than treating every symptom as an HST fault. The engine specifications are also separated into distinct engine groups, making correct engine identification important when performing maintenance or internal component servicing.
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