This is the official Kubota B21, TL421, and BT751 workshop manual, a 437-page PDF for the B21 compact tractor, TL421 front loader, and BT751 backhoe. It carries the D1005-ETLB engine and is split into Mechanism and Servicing parts, so you first learn how each system works, then follow the service procedures.
Coverage runs from the engine, clutch, transmission, and rear axle through the brakes, front axle, steering, hydraulic system, and full electrical system, plus dedicated Front Loader and Backhoe sections. Each area includes troubleshooting, factory specifications, allowable limits, and disassembly and assembly steps.
This is the manual for real shop work: setting valve clearance, chasing a hydraulic or electrical fault, torquing fasteners to spec, and rebuilding the loader or backhoe rather than guessing at it.
What's Inside This Kubota B21, TL421, BT751 Manual
| System | Pages | Key Topics |
|---|---|---|
| To the Reader | - | Kubota Tractor B21, Kubota Front Loader TL421, Kubota Backhoe BT751, PTO, Engine, Hydraulic, Clutch, Transmission |
| General | - | Tractor Identification, Electrical Parts and Wiring, Lubricants, Fuel and Cooling Water, Screws, Bolts and Nuts, Stud Bolts, Hydraulic Hoses Fitting |
| Engine | - | Cylinder Block, Cylinder Head, Crankshaft, Piston and Piston Rings, Connecting Rod, Camshaft, Fuel Camshaft, Rocker Arm |
| Clutch | - | Linkage Mechanism, Operation, Clutch Disc, Pressure Plate Assembly, Release Bearing, Release Hub, Release Fork |
| Transmission | - | Hydrostatic Transmission, PTO System, Differential Gear System, Clutch Housing, Transmission Case, Differential Case |
| Rear Axle | - | Differential Gear Shaft, Ball Bearing, Rear Axle Case, Spur Gear, Differential, Spiral Bevel Gear, Differential Lock Shift Fork |
| Brakes | - | Brake Pedal, Rear Axle Case, Differential Lock Shift Fork, Differential Lock Clutch, 57T Gear, Brake Assembly, Brake Discs, Friction Plate |
| Front Axle | - | Front Wheel Alignment, Propeller Shaft, Drag Link, Front Axle Assembly, Tie-Rod, Axle Bracket, Bevel Gear Case |
| Steering | - | Hydraulic Circuit, Power Steering Body, Drag Link, Pitman Arm, Power Steering Assembly, Ball Nut Assembly, Valve Housing, Sector Gear Shaft |
| Hydraulic System | - | Hydraulic Pump, Flow Priority Valve, Position Control Valve, Hydraulic Block, Hydraulic Cylinder, Relief Valve, Hydraulic Piston, Lowering Speed Adjusting Valve |
| Electrical System | - | Wiring Diagram and Electrical Circuit, Starting System, Engine Key Switch Shut-Off System, Charging System, Lighting System, Easy Checker, Gauge, Opc(operator Presence Control)system |
| Front Loader | - | Safety Decals, Front Loader Terminology, Operating Dimensions, Hydraulic System, Control Valve Assembly, Feedback Linkage, Boom Cylinder, Bucket Cylinder |
| Backhoe | - | Safety Decals, Backhoe Terminology, Operating Dimensions, Cycle Time, Hydraulic Cylinders, Lift Capacity, Hydraulic System, Hydraulic Cylinder |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| TL421 | ||
| Loader side frame mounting screw, bolt and nut tightening torque | 150 to 160 N·m | p. 393 |
| B21 | ||
| Hydraulic oil filter for HST, efficiency | 10 µm | p. 26 |
| Transmission case (Hydraulic Fluid) Capacity | 27.5 L | p. 20 |
| Fan belt tension | 7 to 9 mm (0.28 to 0.34 in.) deflection | p. 35 |
| Battery Cold Cranking Amps | 433 A | p. 33 |
| Main Switch Continuity (ON Position, 30 terminal - AC terminal) | 0 ohm | p. 339 |
| Fuse Capacity (Head lights) | 10 A | p. 41 |
| Main Switch Connector 30 terminal voltage | Approx. battery voltage | p. 339 |
| Thermostat Valve Opening Temperature (At Beginning) | 80.5 to 83.5 °C | p. 134 |
| PTO Power | 10.0 kW (13.5 HP) | p. 8 |
| Engine Oil Capacity (with filter) | 3.0 L | p. 8 |
Kubota B21, TL421, BT751 Common Problems This Manual Covers
Loader raises slowly then speeds up
A TL421 loader arm that creeps up and then jumps to normal speed usually means a hydraulic restriction, old or low fluid, a clogged filter, or a weakening pump. The Hydraulic System section walks the checks and specifications.
Manual Section: 8 Hydraulic System p. 278Weak or erratic backhoe hydraulics
When the BT751 backhoe becomes slow, jerky, or stops responding, the cause is often contaminated fluid, a clogged strainer, a worn control valve, or a failing pump. The Backhoe section covers its cylinders and circuits.
Manual Section: B Backhoe p. 386Blowing fuses on the turn signals
B21 owners report fuses blowing when the turn signals or other circuits are used, which points to shorted wiring, corroded connectors, or a failed switch. The Electrical System section has the diagrams and tests.
Manual Section: 9 Electrical System p. 306Intermittent no-start
A weak battery, corroded terminals, or a fault in the starter circuit can leave a B21 cranking slowly or not at all. Trace it with the starting and charging procedures in this section.
Manual Section: 9 Electrical System p. 306Overheating under load
Dirty radiator fins, low coolant, a stuck thermostat, or a loose fan belt make a working B21 run hot. The Engine section gives the thermostat and cooling specifications.
Manual Section: 1 Engine p. 61Clutch drag or hard shifting
Difficult gear changes or a dragging clutch on the B21 point to clutch wear or adjustment. The Clutch section covers inspection, adjustment, and replacement.
Manual Section: 2 Clutch p. 144Frequently Asked Questions
Which machines does this manual cover?
It covers the Kubota B21 tractor, the TL421 front loader, and the BT751 backhoe, all powered by the D1005-ETLB engine. The 437-page manual treats each as its own section.
Does it include the loader and backhoe, or just the tractor?
All three are covered. There is a dedicated Front Loader section for the TL421 and a Backhoe section for the BT751, in addition to the full tractor coverage. p. 351
Does it list factory torque and clearance specs?
Yes. Each area has servicing specification lists and allowable limits. The Engine section, for example, gives a cold valve clearance of 0.18 to 0.22 mm among its specifications. p. 61
Are wiring diagrams and electrical specs included?
Yes. The Electrical System section includes wiring information, the main switch and fuse specs, and starting and charging system checks. p. 306
What format is this manual in?
Instant PDF download. The full 437-page searchable Shop Manual lands in your hands right after payment, ready to open on a laptop, tablet, or phone out in the shop.
Am I able to print pages from this manual?
Absolutely. No DRM or copy protection. Print the whole manual or just the pages you need. Any home or office printer works.
Can I trace hydraulic lines with this Kubota B21 manual?
Yes. The manual includes full hydraulic schematics with flow diagrams, valve configurations, and pressure specifications.
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