Part of the Yanmar Repair Manuals.
Pull the access panel on a Yanmar LB446HB that cranks fine but leaves the lamps dark, and you are looking at three systems that all have to cooperate: the floodlight projector, the 1.7 kVA generator, and the L48AD EGYSS6H diesel that drives it. This service manual walks all three end to end, from specifications and service standards through disassembly, checking and servicing, troubleshooting, and test run.
The engine chapters read like a rebuild bench sheet: wear limits for the piston, connecting rod, crankshaft and main bearing, tightening torque tables, and adjustment procedures for valve clearance and fuel injection. Guessing a head nut torque on a small diesel is how castings crack and gaskets weep; the factory figures are here instead.
It is a 275 page PDF with 227 bookmarks, so it rides on the phone in your pocket or the laptop at the bench, wherever the LB446H is parked.
What's Inside This Yanmar LB446HB, LB446H, LB446HB/H Manual
| System | Pages | Key Topics |
|---|---|---|
| Floodlight Projector | 2-81 | Cover, Foreword, Contents, Back Cover |
| Generator | 82-146 | Cover, Introduction, Contents, For Safe Operation (Warning Symbols, Safety Precautions, Location of Warning Labels) |
| Cover | 147-148 | Introduction |
| Service Information | 149-151 | General Safety, Serial Number Location, Service Rules |
| Specifications | 152-158 | Cross Sectional Views |
| Service Standard | 159-168 | Intake/Exhaust Valve Seats, Valve Spring, Piston, Connecting Rod, Crankshaft and Main Bearing, Oil Pump (Trochoid Pump) |
| Disassembly and Reassembly | 169-187 | Tools, Meters and Instruments, Tightening Torque, Maintenace Schedule, Disassembly Procedures |
| Checking and Servicing | 188-245 | Cylinder Head, Piston and Piston Pin, Connecting Rod, Crankshaft, Flywheel and Main Bearing |
| Troubleshooting | 246-261 | No Fuel Injection Sound, Low Compression Pressure, Failure of Starter Motor, Insufficiently Charged Battery, Unexpected Reverse Rotation at Startup, Abnormal Exhaust Color |
| Test Run | 262-264 | Before Starting, Starting, Operation, Stopping |
| Helical Inserting Part for Repair | 265-267 | Size of Helical Inserting Part, Drilling, Tapping, Insertion, Where Helical Insert Part CAN Not Be Used |
| Appendix 1 Difference Between Parts Under Spec. S and D | 268-270 | Crank Case Cover, Camshaft Assy, Flywheel, Piston, Cooling Fan Case, Starting Motor |
| Appendix 2 Detail of Special Tools | 271-273 | Oil Seal Fitting Tool, Valve Stem Seal Fitting Tool, Flywheel Tightening Handle, Flywheel Extractor |
| Colophon | 274 | First Edition, Engineering & Development Dept., Construction Equipment Division, Products Support Group, Yanmar Technical Service Co., Ltd. |
| Spine Title | 275 | Yanmar, Service Manual, Model, LB446HB/H |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| LB446H | ||
| Lighting unit assembly nut (M16) tightening torque | 49 to 66 lbw-ft (67 to 90 N-m) | p. 33 |
| All Models | ||
| Lamp replacement part number | 1-3010010-10 | p. 48 |
| Floodlight Projector Rated Voltage | 130 V | p. 14 |
| Floodlight Projector Current | 3.3 x 4 A | p. 14 |
| Floodlight Projector Lamp Rated Life | 20000 h | p. 14 |
| Generator Rated Output | 1.7 kVA | p. 98 |
| Generator Fuel Tank Capacity | 15 L | p. 98 |
| Generator Lube Oil Capacity (Upper Limit) | 0.8 L | p. 98 |
| Intake/Exhaust Valve Head Clearance | 0.15±0.05 mm | p. 126 |
| Fuel Injection Pressure | 19.6 MPa | p. 127 |
| Floodlight Projector Mast Group Bolt Torque (M10X25) | 24 to 33 N-m | p. 38 |
| LB446HB | ||
| Coupler button screw (M10X35) tightening torque (for balloon type) | 24 to 33 lbw-ft (33 to 45 N-m) | p. 31 |
Yanmar LB446HB, LB446H, LB446HB/H Common Problems This Manual Covers
Lamps dead while the engine runs
Burned out bulbs are the cheap fix to rule out before chasing wiring or generator faults. The manual's step by step lamp replacement procedure keeps you from damaging the new bulb on the way in.
Manual Section: 2.11. How to replace light bulb p. 115No voltage at the floodlight terminals
When the lamps and wiring test good but nothing lights, the generator side needs metering. This section gives procedures for measuring floodlight output terminal voltage, no-load voltage, generator voltage, and insulation resistance.
Manual Section: 6. Inspection of generator p. 132Hard starting and low compression
An L48AD that cranks without firing usually comes down to fuel delivery or compression loss. The engine troubleshooting chapter works through no fuel injection sound, low compression pressure, starter motor failure, and abnormal exhaust color symptom by symptom.
Manual Section: 5. Toroubleshooting p. 246Valve clearance drifted out of spec
Lash on a small single cylinder diesel closes up over hours of run time and shows up as hard starting and rough running. The manual covers checking and resetting clearance to the factory figure.
Manual Section: 5.8. Adjustment of Valve clearance p. 126Air locked or dirty fuel system
Run the tank dry once and the injection system needs bleeding before it will fire again. Refueling, fuel filter cleaning, air bleeding, and lube oil service are all covered here in order.
Manual Section: 5. Inspection and Adjustment of Engine p. 121Worn crank and bearings at teardown
Once the engine is on the stand, every measurement is a keep or replace decision. The service standard chapter lists limits for the valve seats and springs, piston, connecting rod, crankshaft and main bearing, and the trochoid oil pump.
Manual Section: 2. Service Standard p. 159Stripped threads in soft castings
An overtightened fastener in an aluminum boss strips long before the bolt complains, and a helical insert saves the part. The manual covers insert sizing, drilling, tapping, insertion, and where inserts cannot be used.
Manual Section: 7. Helical Inserting Part for Repair p. 265Frequently Asked Questions
Which models and engine does this manual cover?
It covers the Yanmar LB446HB and LB446H floodlight projector fitted with the L48AD EGYSS6H diesel engine. The 275 pages span the projector assembly, the 1.7 kVA generator, and full engine service from specifications through troubleshooting and test run.
What is the valve clearance for the engine in the Yanmar LB446HB, LB446H, LB446HB/H?
Intake and exhaust valve head clearance is 0.15±0.05 mm. The Adjustment of Valve clearance section walks through measuring and resetting it as part of the engine inspection procedures. p. 126
Does it give fuel injection pressure and timing?
Yes. The fuel injection valve inspection section specifies 19.6 MPa injection pressure and covers checking pressure and spray condition, with fuel injection timing adjustment covered immediately after. p. 127
Will it help when the generator makes no output?
Yes. The Inspection of generator section covers measuring output terminal voltage, no-load voltage, and insulation resistance to isolate the fault, and the generator disassembly and reassembly procedures cover replacing whatever tests bad. p. 132
Is this Service Manual a digital download?
This is a 275-page searchable PDF ready for immediate download. Works on any device, so pull it up on your phone while you're under the hood. No shipping, no waiting.
Are there any print restrictions on this manual?
Absolutely. No DRM or copy protection. Print the whole manual or just the pages you need. Any home or office printer works.
Does this manual have electrical diagrams?
Yes, this Yanmar LB446HB, LB446H Service Manual includes complete electrical wiring diagrams, wire routing, and connector pinouts.
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