Part of the Kubota Repair Manuals.
This is the Kubota GL Series Diesel Generator Workshop Manual, the factory service manual for the GL3500, GL4500, GL4500-S, GL5500, GL5500-S, and GL6500-S generator sets. These units are built on Kubota's ZB400-GL through ZB600-GL(S) diesel engines in both quiet-type and heavy-duty configurations.
The manual covers the generator mechanism, including the stator and rotor assemblies and the automatic voltage regulator (AVR), along with engine service, the cooling system, servicing specifications, and tightening torques. Troubleshooting and maintenance sections walk through the checks that keep these sets starting and holding output.
For an owner, standby-power installer, or independent technician, this PDF download provides the specifications and repair procedures to diagnose a no-start, chase down low or unstable voltage, and service the engine to factory values. It is text-searchable and prints on standard paper.
What's Inside This Kubota GL3500–GL6500 Series Manual
| System | Pages | Key Topics |
|---|---|---|
| Cover Page | - | WSM Logo, Workshop Manual, Diesel Generator, Gl Series, Kubota |
| Safety Instructions | - | - |
| Specifications | - | Generator Gl-S Series (2 Poles), Engine Zb400-Gl-S, Zb500-Gl-S, Zb600-Gl-S, Generator Gl Series (4 Poles), Engine Zb400-Gl, Zb500-Gl, Zb600-Gl |
| Mechanism | - | F Feature, Generator Units (Quiet Type Series, Heavy Duty Series, Stator Assembly, Rotor Assembly, Avr), Avr (Bias Current Path, Excitation Current Path From the Sub Coil to Rotor) |
| Back Cover | - | Kubota Tractor Corporation, Corporate Office, Western Division, Central Division, Northern Division, Southeast Division, Printed in U.S.A., June 2002 |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| GL3500, GL4500-S | ||
| Cylinder, Head Bolt torque | 39.2 to 44.1 N-m (4.0 to 4.5 kgf-m, 28.8 to 32.5 ft-lbs) | p. 38 |
| Connecting Rod Bolt torque | 14.7 to 18.6 N-m (1.5 to 1.9 kgf-m, 10.8 to 13.7 ft-lbs) | p. 38 |
| All Models | ||
| Fuel filter cleaning interval | Every 150 hours | p. 40 |
| Fuel filter changing interval | Every 1000 hours | p. 40 |
| Air cleaner cleaning interval | Every 75 hours | p. 40 |
| Compressed air pressure for cleaning air cleaner element | under 686 kPa (7 kgf/cm2, 99 psi) | p. 43 |
| Solenoid coil resistance (Normal) | Approx. 2.0 Ω | p. 58 |
| Solenoid coil resistance (Defective) | Approx. 0.5 Ω | p. 58 |
| Water Pump Link-Belt checking interval | Every 200 hours | p. 40 |
| Generator V-Belt checking interval | Every 200 hours | p. 40 |
| GL4500-S | ||
| Battery model | 36B20R(S) | p. 8 |
| Battery capacity 20 HR | 12V-35AH | p. 8 |
Kubota GL3500–GL6500 Series Common Problems This Manual Covers
Low, unstable, or no AC output
Weak, fluctuating, or missing AC power on a GL set points to the generator head, AVR, or wiring. The Mechanism section covers the stator and rotor assemblies and the automatic voltage regulator.
Manual Section: Mechanism p. 11Cranks but will not start
A generator that cranks yet will not fire is usually a fuel-delivery problem such as air in the lines, a clogged fuel filter, or an injection fault. The Troubleshooting section walks through the diagnosis.
Manual Section: TroubleshootingOverheats or shuts down under load
Running hot or shutting down under load traces to low coolant, a restricted radiator, or a belt problem. The Cooling System section covers the checks and the radiator cap test.
Manual Section: Cooling SystemExcessive smoke or loss of power
Black or heavy smoke with poor power usually means a dirty air cleaner, fuel contamination, or worn injectors. The Engine section covers the servicing and specifications for these diesels.
Manual Section: EngineWeak battery or slow cranking
Slow cranking or a battery that keeps going flat traces to the battery, charging circuit, or corroded terminals. The Troubleshooting section covers the electrical checks including the starter solenoid.
Manual Section: TroubleshootingHard starting after long storage
GL sets that sit between uses often start hard because of stale fuel or a clogged fuel filter. The Checking and Maintenance section gives the fuel filter and air cleaner service intervals.
Manual Section: Checking And MaintenanceFrequently Asked Questions
Which generator models and engines does this manual cover?
It covers the Kubota GL3500, GL4500, GL4500-S, GL5500, GL5500-S, and GL6500-S diesel generator sets, built on the ZB400-GL, ZB500-GL, and ZB600-GL engines in standard and quiet-type (S) versions.
What are the cylinder head bolt torque specs?
The manual specifies a cylinder head bolt torque of 39.2 to 44.1 N-m (4.0 to 4.5 kgf-m, 28.8 to 32.5 ft-lbs). Connecting rod and other engine torques are listed in the same tightening torque table. p. 38
Does it cover both 2-pole and 4-pole models?
Yes. The specifications separate the 4-pole GL series that runs at 1800 rpm from the 2-pole GL-S series that runs at 3600 rpm, so you can match data to your set. p. 8
What are the fuel and air filter service intervals?
The manual lists cleaning the fuel filter every 150 hours and replacing it every 1000 hours, and cleaning the air cleaner every 75 hours. Following these intervals prevents hard starting and smoke. p. 40
What do I get after purchasing this Kubota GL3500–GL6500 Series manual?
The download is instant: the complete 80-page searchable Workshop Manual lands the moment your payment clears. Open it on a laptop, tablet, or phone right at the machine.
Can I print specific sections of this manual?
Print whatever you need: single pages, full chapters, or the whole manual. The PDF carries no restrictions.
Are electrical wiring diagrams included in this Kubota GL3500–GL6500 Series?
Yes. Full electrical wiring diagrams, wire routing, and connector pinouts are all in this Kubota GL3500 to GL6500 Series Workshop Manual.
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