Part of the Kubota Repair Manuals.
This is the Kubota BH77 backhoe workshop manual, the factory service book for the BH77 loader-backhoe attachment (publication 9Y121-05440). It focuses on the hydraulic system that drives the boom, dipperstick, bucket, swing, and stabilizers.Its 75 pages move from safety information and machine identification into the mechanism section, which explains the hydraulic circuit, the control valve structure and operation, the overload relief valve, and the hydraulic cylinders. The servicing section then covers troubleshooting, servicing specifications, tightening torques, and full dismounting, disassembly, and assembly procedures.This is the manual to reach for when a boom or swing function loses power, the controls feel vague, or you need relief valve pressures and torque figures to reassemble the backhoe correctly. Lubricant tables and torque values for hydraulic fittings and fasteners are included.
What's Inside This Kubota BH77 Manual
| System | Pages | Key Topics |
|---|---|---|
| Information | - | - |
| General | - | Backhoe Identification, Lubricants, Tightening Torques (Stud Bolts, American Standard Screws, Bolts and Nuts with Unc or Unf Threads, Plugs, Hydraulic Fittings) |
| Mechanism | - | Hydraulic Circuit, Control Valve (Structure, Operation, Overload Relief Valve), Hydraulic Cylinder |
| Servicing | - | Troubleshooting, Servicing Specifications, Tightening Torques |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| Relief valve setting pressure for Boom (A5, B5 port side) | 20.6 to 21.0 MPa (210 to 215 kgf/cm², 2990 to 3050 psi) | p. 48 |
| Tightening torque for Control lever step mounting screw | 48 to 55 N·m (4.9 to 5.7 kgf·m, 36 to 41 lbf·ft) | p. 58 |
| Tightening torque for Hydraulic hose fitting, Flare nut (UNF) 9/16 | 22 to 25 N-m (2.3 to 2.5 kgf-m, 17 to 18 lbf-ft) | p. 20 |
| Transport Height | 2051 mm | p. 11 |
| Maximum Digging Depth | 2378 mm | p. 11 |
| Digging Force (With bucket cylinder) | 15220 N | p. 12 |
| Boom cylinder, extend (Cycle Time) | 3.5 seconds | p. 12 |
| Transmission case capacity (B3200/B3300SU) | 14.5 L | p. 18 |
| Relief Valve Setting Pressure (B3200 Tractor) | 13.3 to 14.3 MPa | p. 48 |
| Swing Frame Fulcrum Pin to Bush (Clearance) | 0.200 to 0.269 mm | p. 48 |
| Thrust Washer (Thickness) | 2.45 to 2.82 mm | p. 49 |
Kubota BH77 Common Problems This Manual Covers
Weak boom or loss of digging force
A boom that will not lift or dig with full force often traces to the main boom hydraulic relief valve; one owner fixed it by replacing that valve. The servicing section lists the relief valve setting pressures and troubleshooting steps.
Manual Section: Servicing p. 46Slow or intermittent swing
Owners report the swing losing power, stopping and starting, or turning very slowly to one side. The mechanism section explains the hydraulic circuit and control valve operation so you can trace the flow restriction.
Manual Section: Mechanism p. 27Sloppy or squeaky controls
After a few hundred hours the control feel can go loose and squeaky as the linkage wears and dries out. The servicing section provides the control lever mounting torques and adjustment procedures.
Manual Section: Servicing p. 46Squeaking or binding pivot joints
Swing and stabilizer joints bind or squeak when the pivots run dry. The general section lists the lubricants and greasing points that keep those joints moving freely.
Manual Section: General p. 14Leaking hydraulic fittings
Seeping hydraulic hose fittings usually mean a flare nut is under or over torqued. The general section gives the tightening torques for hydraulic fittings and hose flare nuts.
Manual Section: General p. 14Frequently Asked Questions
What does this manual cover?
It is the workshop service manual for the Kubota BH77 backhoe attachment, focused on its hydraulic circuit, control valve, and cylinders, with troubleshooting, servicing specifications, and disassembly and assembly procedures.
Does it include tightening torque specs?
Yes. The general section lists tightening torques for stud bolts, UNC and UNF threaded fasteners, plugs, and hydraulic fittings, so you can reassemble the backhoe to spec. p. 14
Does it give hydraulic relief valve pressures?
Yes. The servicing section lists relief valve setting pressures, including the boom port values, along with the oil temperature the settings should be checked at. p. 46
Does it explain how the control valve works?
Yes. The mechanism section covers the control valve structure and operation and the overload relief valve, alongside the full hydraulic circuit and cylinders. p. 27
What format is this manual in?
It's a 75-page searchable PDF, ready to download the moment you buy. Pull it up on any device, including your phone while you're under the hood. No shipping, no waiting.
Am I able to print pages from this manual?
Yes. The PDF carries no DRM restrictions, so you can print any page or section you need for the shop. Any standard printer handles it.
Are there hydraulic schematics in this Kubota BH77 manual?
Full hydraulic system diagrams are included, covering circuits, valve locations, and hydraulic component specs for the Kubota BH77.
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