Looking for authentic OEM diagnostic and repair data for your compact excavator? All 425 pages of this Yanmar B50-2B (US) Service Manual PDF focus on one thing: getting your B50-2B back to the dirt. You get high-resolution hydraulic circuit schematics, detailed electrical wiring diagrams, and a massive troubleshooting section to track down stubborn operational faults. Open the equipment chapters to find step-by-step teardown procedures for the main pump, control valves, and travel motors, backed by page after page of factory calibration tables. Set the fuel injection nozzle pressure between 2844 and 2986 PSI, and secure the retainer clamp bolt to exactly 5.1 to 6.5 ft-lbf before firing up the engine. When your equipment is dead in the yard, guessing just burns through cash. Download this highly organized, bookmarked file, pull it up on your shop tablet, and fix the problem right the first time.
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
Yanmar B50-2B tracks barely move or machine is very weak in travel while other functions work normally
Inspect the hydraulic system relief pressure on page 17. Verify it reaches 2986 PSI (20595 kPa). If pressure is low, test the travel motor and counter-balance valve. Drain and refill the hydraulic oil tank to its 31.2 Gals (118 L) capacity if fluid is contaminated.
Manual Section: Travel Motor TroubleshootingEngine hard starting, rough running, or severe loss of power under load with poor combustion p. 395
Test the fuel injection nozzle injection pressure. Adjust the nozzles to spray between 2844 to 2986 PSI (19614 to 20595 kPa) as specified on page 22. Clean the oil/water separator mesh filter, which requires service every 200 hrs according to the maintenance schedule on page 383.
Manual Section: Engine Troubleshooting (General)Coolant warnings trigger frequently and the engine overheats quickly during normal excavation operations p. 395
Check the fan belt tension. Measure the V-belt deflection and ensure it falls within 0.39 to 0.59 in. (10 to 15mm) as detailed on page 50. Inspect the radiator for blockages and verify the cooling water pipe condition, replacing it every 1000 hrs.
Manual Section: Engine Troubleshooting (General)Boom or upper structure shifts and drifts sideways unexpectedly when the controls are in neutral
Inspect the swing system and hydraulic cylinders for internal leakage. Verify the hydraulic system relief pressure holds at 2986 PSI (20595 kPa) as shown on page 17. Torque the hose clamps at the boom rear to 32.5 to 43.4 ft·lbf (44.1 to 58.8 N·m) using page 45.
Manual Section: Non-breakdowns (Operational Characteristics)Frequently Asked Questions
What is the torque specification for the flywheel installation bolt on the Yanmar B50-2B US model?
The flywheel installation bolt (M10 X 1.25) should be tightened to a torque of 61.4 to 65.1 ft·lbf. (83.3 to 88.2 N·m). This specification is listed under the engine tightening torque for major bolts and nuts.
What are the replacement specifications for the fuel injection nozzle/injector?
The fuel injection nozzle for the Yanmar B50-2B US model has a YDLLA type nozzle with 4 injection holes, each φ0.009 (φ0.23) in. (mm) in diameter. The fuel spray angle is 150 degrees, and the injection pressure should be between 2844 to 2986 PSI (19614 to 20595 kpa).
What are the replacement specifications for the fuel filter?
The fuel filter element should be replaced every 400 hours. The FO filter has a filtration area of 139.5 sq.in. (900 sq.cm) and is a Mesh filter type. It must be installed at a position higher than the fuel injection pump.
What is the engine oil capacity for the Yanmar B50-2B US model?
The engine oil pan capacity for the Yanmar B50-2B US model is 9.41 Ots. (8.9 L). This is the amount of oil to be refilled and changed during maintenance.
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).
Document Quality
This document is a scanned PDF with an OCR layer, allowing you to search and copy the full text. The text quality is crisp and easy to read throughout. Diagrams and illustrations are raster images, but their labels are consistently clear and legible. Pages are generally clean with minimal scan artifacts, and there are no notable stains, marks, or skewed pages. You will find no unexpected blank or filler pages.
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