Part of the Kubota Repair Manuals.
This is the official Kubota workshop manual for the AV1600, AV2500, AV3800, AV4500, AV5500, and AV6500 generators, a 70-page PDF. These units run the GH120, GH170, GH250, GH280, and GH400 engines, and the manual covers both the generator end and the engine.
It opens with specifications, dimensions, and full wiring diagrams, then explains the mechanism, including the oil watching system, auto idler system, and auto choke. From there it moves into disassembling and servicing, with troubleshooting, tightening torques, a maintenance check list, and detailed generator and engine service procedures.
Use it to chase a no-output or unstable-voltage fault, test the field and DC output, set spark plug gap and torque, adjust valve clearance, and rebuild the engine to the factory allowable limits after years of storage or hard use.
What's Inside This Kubota AV1600–AV6500 Series Manual
| System | Pages | Key Topics |
|---|---|---|
| Specifications | 9-12 | Generator, Engine, Standard Voltage, Ampere Frequency, Receptacle |
| Dimensions | 13 | Model, A, B, C |
| Wiring Diagram | 14-22 | Generator, Control Box, Engine, Ignition Control Unit, Receptacle, Color of Wiring |
| Mechanism | 23-28 | Feature (Engine Body, Oil Watching System, Auto Idler System, Auto Choke) |
| Disassembling and Servicing | 29-43 | General (Generator Identification, Lubricants and Fuel, Troubleshooting, Tightening Torques, Maintenance Check List, Check and Maintenance, Special Tools), External Component |
| External Components | 44 | Fuel Tank, Muffler Cover, Muffler, Control Box, Air Cleaner Assy. |
| Generator | 45-50 | Receptacles, Diode Stack, Capacitor, A.v.r., Stator, Rotor, Brush Holder |
| Engine | 51-70 | Checking and Adjusting |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| AV1600, AV2500 | ||
| Cylinder Head Screws Torque (GH120, GH170) | 24.5 to 32.4 N·m | p. 37 |
| All Models | ||
| Air cleaner element replacement interval | Every year or every 6 times of cleaning | p. 38 |
| Fuel filter cleaning interval | Every 200 hours | p. 38 |
| Spark Plug Tightening Torque | 9.8 to 24.5 N·m | p. 37 |
| DC Output Voltage | 8 to 18 V | p. 45 |
| AV5500, AV6500 | ||
| Oil strainer cleaning interval (GH400 only) | Every 200 hours | p. 38 |
| Commutator O.D. (Allowable Limit) | 27.0 mm | p. 69 |
| Brush Length (Allowable Limit) | 6.0 mm | p. 69 |
| Engine Oil Capacity | 1.1 l | p. 10 |
| AV1600, AV2500, AV3800, AV4500 | ||
| Spark plug gap (GH120, GH170, GH250, GH280) | 0.6 to 0.7 mm | p. 40 |
| AV3800, AV4500, AV5500, AV6500 | ||
| Field Voltage (Checking under the no load) | 15 to 40 (V) D.C. | p. 46 |
| AV1600 | ||
| Engine Oil Capacity | 0.55 l | p. 9 |
Kubota AV1600–AV6500 Series Common Problems This Manual Covers
No or unstable output after storage
An AV unit that runs but makes little or unstable AC output often has an AVR, winding, or brush and slip ring problem. The Generator section covers checking and servicing the alternator end.
Manual Section: Generator p. 45Engine cranks but will not start
Stale or contaminated fuel, a clogged filter, air in the lines, or a stop circuit fault will keep the engine from firing. Work through the troubleshooting in the Disassembling and Servicing section.
Manual Section: Disassembling and Servicing p. 29Voltage collapses under load
Output that drops badly when a load is applied can be an overloaded set, a failing governor, or a dirty air filter pulling engine speed down. The Engine section covers the speed and running checks.
Manual Section: Engine p. 51Hard starting or rough running
Hard starting and rough running point to worn injection or ignition parts, incorrect valve clearance, or low compression. The Engine section gives the checking, adjusting, and servicing steps.
Manual Section: Engine p. 51Isolating engine, AVR, or winding faults
Owners often cannot tell whether an output problem is in the engine, the AVR, or the alternator windings. The wiring diagrams trace every circuit so you test the right part.
Manual Section: Wiring Diagram p. 14Noise or vibration from wear
Growling or vibration on an older set usually comes from worn bearings or perished mounting rubbers. The Generator section covers inspecting and replacing these parts.
Manual Section: Generator p. 45Frequently Asked Questions
Which generators and engines does it cover?
It covers the Kubota AV1600, AV2500, AV3800, AV4500, AV5500, and AV6500 generators, running the GH120, GH170, GH250, GH280, and GH400 engines, in one 70-page manual.
Are wiring diagrams included?
Yes. A full Wiring Diagram section maps the generator, control box, engine, ignition control unit, and receptacle wiring with wire colors. p. 14
Does it list spark plug and torque specs?
Yes. The Disassembling and Servicing section gives tightening torques, including a spark plug torque of 9.8 to 24.5 N-m, and the spark plug gap for each engine. p. 29
Can I test the output voltage and AVR with it?
Yes. The Generator section covers checking the field voltage and DC output and servicing the alternator end when output is missing or unstable. p. 45
What exactly do I receive with this Kubota AV1600–AV6500 Series Workshop Manual?
Instant PDF download. The full 70-page searchable Workshop Manual is yours immediately after payment. Open it on a laptop, tablet, or phone right there in the shop.
Is this Kubota AV1600–AV6500 Series manual print-friendly?
No restrictions at all. Print individual pages, full chapters, or the entire manual. The PDF is completely unlocked.
Is there a wiring diagram in this Kubota AV1600–AV6500 Series Workshop Manual?
Included. The Kubota AV1600, AV6500 Workshop Manual covers complete wiring harness diagrams, electrical circuits, and connector pinouts.
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