Part of the Yanmar Repair Manuals.
Chase a weak boom on a Yanmar YB401W long enough and you end up at the control valve, and this service manual supplement is where Yanmar documented it. Written for the YB401W wheel backhoe from serial number 50001 onward with the 4TNA78TL-DBW or 4TNA78TL-RBW engine, it walks the machine system by system: electrical components, engine, control valve, clutch valve, shut off valve (suspension lock valve), and steering.
Alongside maintenance procedures for each part, it carries technical data (specifications, engine maintenance standards, tightening torques), adjustment procedures including toe-in and steering angle, fuel oil and power transmission system diagrams, and a periodic replacement schedule for vital aging parts. When a steering cylinder starts weeping, that schedule tells you it takes a complete seal set, so you order the right parts the first time.
The file is a 64 page English PDF, 4.8 MB, with 65 bookmarks for quick navigation. Download it instantly and print the pages you need for the bench.
Complete the set for your YB401W
- Parts Catalog: Yanmar YB401W Parts Catalog (incl. Wiring)
What's Inside This Manual
| System | Pages | Key Topics |
|---|---|---|
| Technical Data | Engine Maintenance Standards, Tightening Torque Of Main Parts | |
| Maintenance Procedure for Each Part | Electrical Components, Engine, Control Valve, Clutch Valve, Shut Off Valve (Suspension Lock Valve), Steering System, Revolving System, Work Equipment | |
| Adjustment Procedure for Each Part | Toe-in Adjustment, Fuel Oil System Diagram, Power Transmission System Diagram, Periodic Replacement Of Vital Aging Parts | |
| Reference | Assembly Procedure Of Collet Joint, Disassembly/Assembly Of Front Open Type Cab |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| Cylinder head main bolt tightening torque | 750~850 Kg-cm (74~83 N-m) | p. 16 |
| OK monitor buzzer behavior for multiple abnormal sensors | When several sensors become abnormal simultaneously, the buzzer sounds intermittently for 10 seconds from the time when the first sensor become abnormal. | p. 22 |
| Hydraulic oil intake filter type | Wire mesh type SFB-16 | p. 10 |
| Hydraulic hose for steering replacement period | Every 2 years | p. 54 |
| Steering cylinder packing, dust seal, O-ring replacement period | Every 2 years | p. 54 |
| Permissible clearance between pin and bushing | 1.0 mm | p. 48 |
| Fan belt tension | 10 ~ 15 kg | p. 14 |
| Engine Plunger Diameter | 8.0 mm | p. 5 |
| Battery Voltage-Capacity | 12V 80AH | p. 6 |
| Overall Length (transporting posture) | 5,430 mm | p. 7 |
| Maximum Digging Depth | 3,230 mm | p. 7 |
