Part of the Yanmar Repair Manuals.
Trace a fault on a Yanmar B50-2B from the pilot valve to the travel motor and you need a document that walks the whole excavator end to end. This service manual covers measurement and adjustment on the 4TNE88B-1 diesel, the fuel supply and electrical systems, hydraulic circuit operation and pressure adjustment, and full teardown procedures for the hydraulic pump, control valve, pilot valve, swing motor and travel motor.
Most people who buy it work on the machine alone, with no dealer tech to ask. Servicing standards, torque tables and a symptom-based troubleshooting chapter mean you are not guessing at clearances or relief settings while a crew waits on the machine.
It applies to the US-spec B50-2B from serial number 65001 onward: 425 pages, Yanmar publication 42698080, delivered as a PDF. Keep it on the laptop in the truck or print the pages you need; it goes wherever the machine is.
What's Inside This Yanmar B50-2B (US) Manual
| System | Pages | Key Topics |
|---|---|---|
| General Cautions for Maintenance Work | 6-14 | 1-1 Correct Work, 1-2 Safety Precautions, 1-3 Preparations, 1-4 Cautions for Disassembly and Reassembly, 1-5 Cautions for Attaching and Detaching Hydraulic Equipment |
| Technical Data | 15-26 | 2-1 Specifications, 2-2 External Drawings and Working Ranges, 2-3 Weight of Main Parts, 2-4 Lifting Capacities |
| Servicing Standards | 27-45 | 3-1 Machine Performance, 3-2 Engine, 3-3 Undercarriage, 3-4 Control Devices, 3-5 Hydraulic Equipment, 3-6 Work Implement, 3-7 Torque Specifications |
| Engine | 46-105 | 4-1 Measurement, Inspection and Adjustment, 4-2 Measuring Process, Service Data and Corrective Action, 4-3 Precautions Reassembly, 4-4 Fuel Supply System, 4-5 Electrical Equipment |
| Hydraulic System | 106-149 | 5-1 Outline, 5-2 Hydraulic Circuit Schematic(with P.T.O. Selector Valve), 5-3 Circuit Operation, 5-4 Pressure Adjustment |
| 6-1 Hydraulic Pump | 151-183 | Hydraulic Pump, Valve Assembly, Pilot Oil Relief Valve, Oil Intake Port, Pilot Oil Discharge Port, Valve Ass'y, Solenoid Valve, Disc Filter |
| 6-2 Control Valve | 184-228 | Control Valve, Right Valve Group, Center Valve Group, Left Valve Group, Bucket, Boom, Travel (R), Inlet |
| 6-3 Pilot Valve | 229-255 | Pilot Valve, Pressure Reducing Valve Section, Handle Section, Port Plate, Spool, Handle, Push Rod, Joint |
| 6-4 Swing Motor | 256-285 | Swing Motor, Hydraulic Motor, Mechanical Brake, Check Valve, Relief Valve, Reduction Gear |
| 6-5 Travel Motor | 286-328 | Travel Motor, Hydraulic Equipment, Counter-Balance Valve, Relief Valve, Two-Speed Switch Mechanism, Reduction Gear, Exploded View and List of Parts, Special Tools |
| Adjustment Procedures for Each Equipment | 329-380 | 7-1 Electeic Equipment of the Machine, 7-2 Undercarriage, 7-3 Controls, 7-4 Swing System |
| Periodic Inspection and Servicing | 381-383 | List of Periodic Inspection and Servicing |
| Fuel,Lube Oil and Grease Recommended | 384-386 | 9-1 Fuel, Lube Oil and Grease Recommended by Yanmar, 9-2 Cooling Water Recommended by Yanmar |
| Troubleshooting | 387-425 | 10-1 Non-Breakdowns, 10-2 Troubleshooting, Reference Data |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| Fuel injection nozzle injection pressure | 2844 to 2986 PSI (19614 to 20595 kPa) | p. 22 |
| Fuel injection nozzle injection hole dia. X no. of holes | φ0.009 (φ0.23) X 4 in. (mm) | p. 22 |
| FO filter filtration area | 139.5 (900) sq.in. (sq.cm) | p. 21 |
| Fuel filter element replacement interval | Every 250 hrs | p. 382 |
| Oil/water separator type | Mesh filter | p. 21 |
| Oil/water separator cleaning interval | Every 200 hrs | p. 383 |
| LO filter filtration area | 155 (1000) sq.in. (sq.cm) | p. 21 |
| Engine oil filter element replacement interval | Every 400 hrs | p. 383 |
| Air cleaner type | Cyclone type | p. 21 |
| Air cleaner filtration area | 11.84 (1.1) sq.ft. (sq.m) | p. 21 |
| Fan belt size | A37 | p. 21 |
| V-belt deflection | 0.39 to 0.59 in. (10 to 15mm) | p. 50 |
Yanmar B50-2B (US) Common Problems This Manual Covers
Tracks barely move under load
Weak travel with other functions still working is a complaint B50 owners report on the forums. The Hydraulic Equipment chapter gives disassembly, inspection and service data for the travel motor so you can find the wear instead of swapping parts blind.
Manual Section: 6 Hydraulic Equipment p. 150Boom drifts or shifts sideways
A boom that creeps or shifts under load usually points to internal leakage in a cylinder or valve. The Troubleshooting chapter works from the symptom back to the likely cause before you open anything up.
Manual Section: 10 Troubleshooting p. 387Weak, slow hydraulic functions
Low or drifting main relief pressure makes the whole machine feel tired. The Hydraulic System chapter explains circuit operation and gives the pressure adjustment procedure, with the system relief setting listed at 2986 PSI (20595 kPa).
Manual Section: 5 Hydraulic System p. 106Hard starting and rough running
Fouled injection nozzles and fuel system faults are the usual suspects on the 4TNE88B-1. The Engine chapter covers nozzle testing and the fuel supply system, with an injection opening pressure of 2844 to 2986 PSI to check against.
Manual Section: 4 Engine p. 46Track tension out of adjustment
Loose tracks throw and accelerate undercarriage wear; overtight ones load the final drives. The undercarriage procedures in the adjustment chapter show how to set tension correctly.
Manual Section: 7 Adjustment Procedures for Each Equipment p. 329Water and dirt in the fuel
Contaminated fuel is a recurring cause of power loss and smoke on these machines. The periodic servicing list schedules oil/water separator cleaning every 200 hours and fuel filter element replacement every 250 hours to stay ahead of it.
Manual Section: 8 Periodic Inspection and Servicing p. 381Frequently Asked Questions
Which machines does this manual cover?
The US-spec Yanmar B50-2B excavator from serial number 65001 onward, fitted with the Yanmar 4TNE88B-1 diesel engine. It is Yanmar service publication 42698080, written in English.
Does it cover hydraulic pressure testing and adjustment?
Yes. The Hydraulic System section covers circuit operation and pressure adjustment, and the technical data lists the system relief pressure at 2986 PSI (20595 kPa), so you can verify a weak machine against the factory setting. p. 106
Are torque specifications included?
Yes. The Servicing Standards section includes a torque specification table, with engine values such as cylinder head bolt torque of 62.9 to 67.8 ft·lbf and connecting rod bolt torque of 32.5 to 36.1 ft·lbf. p. 27
Does it list maintenance intervals?
The Periodic Inspection and Servicing section gives hour-based intervals: fan belt tension check every 50 hours, oil/water separator cleaning every 200 hours, fuel filter element every 250 hours, and engine oil filter and air cleaner element replacement every 400 hours. p. 381
How quickly can I access this manual after buying?
You get a 425-page searchable PDF that downloads instantly after checkout. Open it on your laptop, tablet, or phone, and bring it right to the shop floor.
Can I print specific sections of this Service Manual?
The PDF is DRM-free. Print whatever sections you need to take out to the shop. Standard letter or A4 paper works.
Does this Yanmar B50-2B (US) manual include hydraulic schematics?
Full hydraulic system diagrams are included, covering circuits, valve locations, and hydraulic component specs for the Yanmar B50-2B (US).
Reviews
There are no reviews yet.