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Cummins Onan KY Generator MicroLite 4000 Series Service Repair Manual INSTANT
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Printed U.S.A.
981-0503
2Ć97
MicroLite 4000 Series
KY

Table of Contents
i
SECTION TITLE PAGE
SAFETY PRECAUTIONS iii . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1 INTRODUCTION 1-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2 SPECIFICATIONS 2-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3 DIMENSIONS AND CLEARANCES 3-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4 TORQUE SPECIFICATIONS 4-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5 PREPARING FOR SERVICE 5-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Troubleshooting 5-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Special Tools 5-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Safety Considerations 5-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Set Removal Guidelines 5-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6 TROUBLESHOOTING 6-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Introduction 6-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Generator Troubleshooting 6-28 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Engine Primary Systems Troubleshooting 6-32 . . . . . . . . . . . . . . . . . . . . . . . . . .
7 CONTROL 7-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Introduction 7-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Control Description 7-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Control Operation 7-3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Control Component Tests 7-5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8 PRIMARY ENGINE SYSTEMS 8-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Introduction 8-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Cooling System 8-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Exhaust System 8-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Ignition System 8-6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Crankcase Ventilation System 8-8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Governor 8-9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Gasoline Fuel System 8-11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
LPG Fuel System 8-21 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Electric Starter 8-25 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
The engine exhaust from this product
contains chemicals known to the State
of California to cause cancer, birth
defects or other reproductive harm.
! !

ii
9 GENERATOR 9-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Generator Description 9-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Generator Operation 9-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Generator Service 9-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Generator Testing 9-8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Voltage Regulator (VR1) Test 9-12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Brushes and Slip Rings 9-12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Rotor Bearing Replacement 9-13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10 ENGINE BLOCK ASSEMBLY 10-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Introduction 10-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Leak Down Test 10-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Oil Pan and Oil Level Switch 10-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Head Cover 10-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Rocker Arms, Push Rods and Cylinder Head 10-3 . . . . . . . . . . . . . . . . . . . . . . .
Valve System 10-4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Crankcase Cover 10-8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Governor 10-8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Camshaft, Tappet and Balancer Removal 10-9 . . . . . . . . . . . . . . . . . . . . . . . . . .
Piston and Crankshaft 10-9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Inspection of Engine Parts 10-10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Piston and Crankshaft Installation 10-17 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Bearings 10-19 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Oil Seal 10-19 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Compression Release System 10-20 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11 SERVICE CHECKLIST 11-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
General 11-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Mounting 11-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Lubrication 11-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Wiring 11-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Initial Start Adjustments 11-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Exhaust System 11-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fuel System 11-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Output Check 11-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Control 11-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Mechanical 11-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12 WIRING SCHEMATIC/DIAGRAM 12-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Safety Precautions
iii
Thoroughly read the SERVICE MANUAL before servic-
ing the genset. Reliable service can be obtained only
with close adherance to the procedures in this manu-
al.
The following symbols in this Manual alert you to potential
hazards to the operator, service person and equipment.
Alerts you to an immediate hazard which
will result in severe personal injury or death.
WARNING
Alerts you to a hazard or unsafe practice
which can result in severe personal injury or death.
CAUTION
Alerts you to a hazard or unsafe practice
which can result in personal injury or equipment dam-
age.
Electricity, fuel, exhaust, moving parts and batteries pres-
ent hazards which can result in severe personal injury or
death.
GENERAL PRECAUTIONS
• Keep ABC fire extinguishers handy.
• Make sure all fasteners are secure and torqued prop-
erly.
• Keep the genset and its compartment clean. Excess
oil and oily rags can catch fire. Dirt and gear stowed in
the compartment can restrict cooling air.
• Before working on the genset, disconnect the nega-
tive ( –) battery cable at the battery to prevent starting.
• Use caution when making adjustments while the gen-
set is running—hot, moving or electrically live parts
can cause severe personal injury or death.
• Used engine oil has been identified by some state and
federal agencies as causing cancer or reproductive
toxicity. Do not ingest, inhale, or contact used oil or its
vapors.
• Benzene and lead in some gasolines have been iden-
tified by some state and federal agencies as causing
cancer or reproductive toxicity. Do not ingest, inhale
or contact gasoline or its vapors.
• Do not work on the genset when mentally or physical-
ly fatigued or after consuming alcohol or drugs.
• Carefully follow all applicable local, state and federal
codes.
GENERATOR VOLTAGE IS DEADLY!
• Generator output connections must be made by a
qualified electrician in accordance with applicable
codes.
• The genset must not be connected to the public utility
or any other source of electrical power. Connection
could lead to electrocution of utility workers, damage
to equipment and fire. An approved switching device
must be used to prevent interconnections.
• Use caution when working on live electrical equip-
ment. Remove jewelry, make sure clothing and shoes
are dry and stand on a dry wooden platform on the
ground or floor.
FUEL IS FLAMMABLE AND EXPLOSIVE
• Keep flames, cigarettes, sparks, pilot lights, electrical
arc-producing equipment and switches and all other
sources of ignition well away from areas where fuel
fumes are present and areas sharing ventilation.
• Fuel lines must be secured, free of leaks and sepa-
rated or shielded from electrical wiring.
• Use approved non-conductive flexible fuel hose for
fuel connections at the genset.
ENGINE EXHAUST IS DEADLY!
• Learn the symptoms of carbon monoxide poisoning in
this Manual.
• Never sleep in the vehicle while the genset is running
unless the vehicle has a working carbon monoxide
detector.
• The exhaust system must be installed in accordance
with the genset Installation Manual.
• Do not use engine cooling air to heat the vehicle interi-
or.
• Make sure there is ample fresh air when operating the
genset in a confined area.
MOVING PARTS CAN CAUSE SEVERE PERSONAL
INJURY OR DEATH
• Do not wear loose clothing or jewelry near moving
parts such as PTO shafts, fans, belts and pulleys.
• Keep hands away from moving parts.
• Keep guards in place over fans, belts, pulleys, etc.
BATTERY GAS IS EXPLOSIVE
• Wear safety glasses and do not smoke while servic-
ing batteries.
• When disconnecting or reconnecting battery cables,
always disconnect the negative (–) battery cable first
and reconnect it last to reduce arcing.
MBL-2

iv

1. Introduction
1-1
This is the service manual for the KY 4000 Series
MicroLite generator sets (gensets). Read and
carefully observe all of the instructions and precau-
tions in this manual.
WARNING
Improper service or parts replace-
ment can lead to severe personal injury or death
and to damage to equipment and property. Ser-
vice personnel must be qualified to perform
electrical and mechanical service.
WARNING
Unauthorized modifications or re-
placement of fuel, exhaust, air intake or speed
control system components that affect engine
emissions are prohibited by law in the State of
California.
WARNING
LPG (liquified petroleum gas) is
flammable and explosive and can cause as-
phyxiation. NFPA 58, Section 1.6 requires all
persons handling LPG to be trained in proper
handling and operating procedures.
See the Operator’s Manual for instructions con-
cerning operation, maintenance and storage and
for recommendations concerning engine lubricat-
ing oil and fuel.
See the Installation Manual for important recom-
mendations concerning the installation and for a list
of the installation codes and standards for safety
which may be applicable.
See the Parts Manual for parts identification num-
bers and required quantities and for exploded views
of the genset subassemblies. Genuine Onan re-
placement parts are recommended for best results.
When contacting Onan for parts, service or product
information, be ready to provide the model number
and the serial number, both of which appear on the
genset nameplate (Figure 1-1). Each character of
these numbers is significant (Figures 1-2 and 1-3 on
Page 1-2).
SN5304U1G2RA 304 cc
A953123456
NAMEPLATE WITH TYPICAL MODEL AND
SERIAL NUMBER DATA
4KYFA26100E
FIGURE 1-1. TYPICAL NAMEPLATE
MicroLite is a trademark of the Onan Corporation.

1-2
Model Number Identification
Figure 1-2 shows a breakdown of the model num-
ber for a typical genset.
MODEL
NO.
4 KY FA 26100 E
1 2 3 4 5 6
1. Power capacity in kilowatts - (4000 watts)
2. Product family designation.
3. Starting method - (Remote startable)
4. Voltage and frequency code - (120 volt,
60-Hz )
5. Specification number - (Code for options and
special features)
6. Specification letter - (Used to identify major
design or manufacturing changes)
FIGURE 1-2. MODEL NUMBER IDENTIFICATION
Serial Number Identification
Figure 1-3 shows a breakdown of the serial number
for a typical genset.
SERIAL
NO.
D 95 3 123456
1 2 3 4
1. Month genset was built:
A = January
B = February
etc.
2. Year genset was built:
94 = 1994
95 = 1995
etc.
3. Location where genset was built:
0 = Fridley, Minnesota
3 = Huntsville, Alabama
4. Active serial number
FIGURE 1-3. SERIAL NUMBER IDENTIFICATION

2. Specifications
2-1
GASOLINE MODELS LPG MODELS
4.0 KY 3.6 KY 3.6 KY 3.3 KY
GENERATOR: 2-Pole Revolving Field, Self-Excited, Electronically Regulated, 1-Phase
Power 4000 watts 3600 watts 3600 watts 3300 watts
Frequency 60 Hertz 50 Hertz 60 Hertz 50 Hertz
Voltage 100/120 volts 100/220/230 volts 100/120 volts 100/220/230 volts
Current 40/33.3 amperes
36/16.4/15.7
amperes
36/30 amperes
33/15.0/14.3
amperes
Speed 3600 rpm 3000 rpm 3600 rpm 3000 rpm
FUEL CONSUMPTION: Gasoline LPG
No load
Half load
Full load
0.29 gph (1.1 l/h)
0.48 gph (1.8 l/h)
0.71 gph (2.7 l/h)
0.21 gph (0.8 l/h)
0.37 gph (1.4 l/h)
0.58 gph (2.2 l/h)
1.5 lbs/h (0.7 kg/h)
2.4 lbs/h (1.1 kg/h)
3.1 lbs/h (1.4 kg/h)
1.1 lbs/h (0.5 kg/h)
2.2 lbs/h (1.0 kg/h)
2.9 lbs/h (1.3 kg/h)
ENGINE: 1-Cylinder, 4-Cycle, Spark-Ignited, OHV, Air Cooled
Bore 3.11 inch (79 mm) 3.11 inch (79 mm)
Stroke 2.44 inch (62 mm) 2.44 inch (62 mm)
Displacement 18.5 inch
3
(304 cc) 18.5 inch
3
(304 cc)
Compression Ratio 8.5 : 1 8.5 : 1
Oil Capacity (Beginning Spec B)* 1.6 quart (1.5 l) 1.6 quart (1.5 l)
Oil Capacity (Spec A)* 1.7 quart (1.6 l) 1.7 quart (1.6 l)
Intake Valve Clearance (Cold) 0.002 inch (0.05 mm) 0.002 inch (0.05 mm)
Exhaust Valve Clearance (Cold) 0.002 inch (0.05 mm) 0.002 inch (0.05 mm)
Spark Plug Gap 0.025 inch (0.64 mm) 0.020 inch (0.51 mm)
Spark Plug Tightening Torque 13 lbs-ft (17 N-m) 13 lbs-ft (17 N-m)
Ignition Timing (magneto type igni-
tion)
25° BTDC, non-adjustable 25° BTDC, non-adjustable
LPG Vapor
Supply Pressure (Range)
–
9 to 13 inch (229 to 330 mm)
W.C. (water column)
DC SYSTEM:
Nominal Battery Voltage 12 volts 12 volts
Minimum Battery Cold Cranking
Capacity: Above/Below Freezing
360/450 amperes 360/450 amperes
Control Fuse 5 amperes 5 amperes
Maximum Regulated-Voltage Bat-
tery Charging Current
– 10 amperes – 10 amperes
* –See Periodic Maintenance in the Operator’s Manual for oil filling instructions.

2-2

3. Dimensions and Clearances
3-1
All clearances are at 70° F (21° C) room temperature. All measurements are listed in inches with
millimeter measurements in parentheses. Measurements are for standard size parts.
FACTORY SPECIFICATION ALLOWABLE
DESCRIPTION MIN. MAX. LIMIT
Cylinder Head
Cylinder Head Distortion – – 0.0157
– – (0.4)
Cylinder Block
Cylinder Bore I.D. 3.1102 3.1110 3.1138
(79.00) (79.02) (79.09)
Crankshaft
Connecting Rod Journal O.D. 1.3177 1.3181 1.3157
(33.47) (33.48) (33.42)
Side Clearance – – 0.0098
– – (0.25)
Connecting Rod
Piston Pin Bore I.D. 0.7093 0.7096 0.7106
(18.015) (18.025) (18.050)
Large Bore I.D. 1.3189 1.3199 1.3204
(33.500) (33.525) (33.540)
Large Bore Clearance 0.0008 0.0022 0.0047
(0.020) (0.055) (0.120)
Side Clearance on Crankshaft 0.0157 0.0433 0.0590
(0.40) (1.10) (1.5)
Camshaft
Lobe Height (Intake and Exhaust) 1.4035 1.4059 1.3997
(35.65) (35.71) (35.55)
Piston
Piston Skirt O.D. 3.1089 3.1094 3.1063
(78.965) (78.98) (78.90)
Pin Bore I.D. 0.7084 0.7087 0.7084/0.7087
(17.994) (18.002) (17.994/18.002)
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Cummins Onan KY Generator MicroLite 4000 Series Service Repair Manual is an essential electronic resource for both professional mechanics and DIY enthusiasts. This comprehensive manual provides detailed information for servicing and repairing the Cummins Onan KY Generator MicroLite 4000 Series.
The manual covers a wide range of topics including:
- Introduction
- Specifications
- Dimensions and Clearances
- Torque Specifications
- Preparing for Service
- Troubleshooting
- Control
- Primary Engine Systems
- Generator
- Engine Block Assembly
- Service Checklist
- Wiring Schematic / Diagram
This manual is meticulously written in a step-by-step format, providing clear instructions for easy repairs. It is available in a file format compatible with all versions of Windows and Mac, and can be viewed using Adobe Reader.