JLG 26MRT Installation and user guide

SERVICE & MAINTENANCE
Model
26MRT
3120791
December 1, 2000
AUSTRALIAN OFFICE
JLG INDUSTRIES, INC.
P.O. Box 5119
11 Bolwarra Road
Port Macquarie, Australia
Telephone: [phone]
Fax: [phone]
EUROPEAN OFFICE
JLG INDUSTRIES (EUROPE)
Kilmartin Place,
Tannochside Park
Uddingston, Scotland, G71 5PH
Telephone: [phone]
Main Fax: [phone]
Parts Fax: [phone]
CORPORATE OFFICE
JLG INDUSTRIES, INC.
1 JLG Drive
McConnellsburg, PA.
17233-9533
USA
Telephone: (717) 485-
5161
Fax: [phone]

INTRODUCTION - MAINTENANCE SAFETY PRECAUTIONS
3120791 – JLG Sizzor – a
SECTION A. INTRODUCTION - MAINTENANCE SAFETY
PRECAUTIONS
A.A GENERAL
This section contains the general safety precautions
which must be observed during maintenance of the
aerial platform. It is of utmost importance that main-
tenance personnel pay strict attention to these warn-
ings and precautions to avoid possible injury to
themselves or others, or damage to the equipment.
A maintenance program must be followed to ensure
that the machine is safe to operate.
MODIFICATION OF THE MACHINE WITHOUT CERTIFI-
CATION BY A RESPONSIBLE AUTHORITY THAT THE
MACHINE IS AT LEAST AS SAFE AS ORIGINALLY
MANUFACTURED, IS A SAFETY VIOLATION.
The specific precautions to be observed during
maintenance are inserted at the appropriate point in
the manual. These precautions are, for the most
part, those that apply when servicing hydraulic and
larger machine component parts.
Your safety, and that of others, is the first consider-
ation when engaging in the maintenance of equip-
ment. Always be conscious of weight. Never attempt
to move heavy parts without the aid of a mechanical
device. Do not allow heavy objects to rest in an
unstable position. When raising a portion of the
equipment, ensure that adequate support is pro-
vided.
SINCE THE MACHINE MANUFACTURER HAS NO
DIRECT CONTROL OVER THE FIELD INSPECTION
AND MAINTENANCE, SAFETY IN THIS AREA RESPON-
SIBILITY OF THE OWNER/OPERATOR.
A.B HYDRAULIC SYSTEM SAFETY
It should be noted that the machines hydraulic sys-
tems operate at extremely high potentially danger-
ous pressures. Every effort should be made to
relieve any system pressure prior to disconnecting
or removing any portion of the system.
Relieve system pressure by cycling the applicable
control several times with the engine stopped and
ignition on, to direct any line pressure back into the
reservoir. Pressure feed lines to system components
can then be disconnected with minimal fluid loss.
A.C MAINTENANCE
FAILURE TO COMPLY WITH SAFETY PRECAUTIONS
LISTED IN THIS SECTION MAY RESULT IN MACHINE
DAMAGE, PERSONNEL INJURY OR DEATH AND IS A
SAFETY VIOLATION.
• NO SMOKING IS MANDATORY. NEVER REFUEL DUR-
ING ELECTRICAL STORMS. ENSURE THAT FUEL CAP
IS CLOSED AND SECURE AT ALL OTHER TIMES.
• REMOVE ALL RINGS, WATCHES AND JEWELRY
WHEN PERFORMING ANY MAINTENANCE.
• DO NOT WEAR LONG HAIR UNRESTRAINED, OR
LOOSE-FITTING CLOTHING AND NECKTIES WHICH
ARE APT TO BECOME CAUGHT ON OR ENTANGLED
IN EQUIPMENT.
• OBSERVE AND OBEY ALL WARNINGS AND CAU-
TIONS ON MACHINE AND IN SERVICE MANUAL.
• KEEP OIL, GREASE, WATER, ETC. WIPED FROM
STANDING SURFACES AND HAND HOLDS.
• USE CAUTION WHEN CHECKING A HOT, PRESSUR-
IZED COOLANT SYSTEM.
• NEVER WORK UNDER AN ELEVATED BOOM UNTIL
BOOM HAS BEEN SAFELY RESTRAINED FROM ANY
MOVEMENT BY BLOCKING OR OVERHEAD SLING,
OR BOOM SAFETY PROP HAS BEEN ENGAGED.
• BEFORE MAKING ADJUSTMENTS, LUBRICATING OR
PERFORMING ANY OTHER MAINTENANCE, SHUT
OFF ALL POWER CONTROLS.
• BATTERY SHOULD ALWAYS BE DISCONNECTED
DURING REPLACEMENT OF ELECTRICAL COMPO-
NENTS.
• KEEP ALL SUPPORT EQUIPMENT AND ATTACH-
MENTS STOWED IN THEIR PROPER PLACE.
• USE ONLY APPROVED, NONFLAMMABLE CLEANING
SOLVENTS.

INTRODUCTION - MAINTENANCE SAFETY PRECAUTIONS
b– JLG Sizzor – 3120791
REVISON LOG
Original Issue - June 1993
Revised - May 19, 1999
Revised - December 6, 1999

3120791 – JLG Sizzor – i
TABLE OF CONTENTS
TABLE OF CONTENTS
SUBJECT - SECTION, PARAGRAPH PAGE NO.
SECTION A - INTRODUCTION - MAINTENANCE SAFETY PRECAUTIONS
A.A General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .aa
A.B Hydraulic System Safety. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .aa
A.C Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .aa
SECTION 1 - SPECIFICATIONS
1.1 Capacities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-1
1.2 Component Data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-1
1.3 Performance Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-1
1.4 Torque Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-2
1.5 Lubrication. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-2
1.6 Cylinder Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-3
1.7 Pressure Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-3
1.8 Serial Number Locations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-3
1.9 Limit Switches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-3
1.10 Major Component Weights. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-3
1.11 Critical Stability Weights . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-3
SECTION 2 - PROCEDURES
2.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-1
2.2 Servicing and Maintenance Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-1
2.3 Lubrication Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-2
2.4 Cylinders - Theory Of Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-3
2.5 Valves - Theory Of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-3
2.6 Component Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-4
2.7 Wear Pads. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-4
2.8 Cylinder Checking Procedures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-4
2.9 Lift Cylinder Removal and Installation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-5
2.10 Lift Cylinder Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-5
2.11 Steer Cylinder Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-10
2.12 Tilt Alarm Switch Adjustment (If Equipped) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-12
2.13 Limit Switch Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-13
2.14 Pressure Setting Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-13
2.15 Drive Axle Repair. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-14
2.16 Brake Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-23
2.17 Throttle Checks and Adjustments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-26
2.18 Control Card Setup and Test Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-26
2.19 Valve Driver Card Setup Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-29
2.20 Preventive Maintenance and Inspection Schedule. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-31
SECTION 3 - TROUBLESHOOTING
3.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-1
3.2 Troubleshooting Information. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-1
3.3 Hydraulic Circuit Checks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-1

ii – JLG Sizzor – 3120791
TABLE OF CONTENTS
LIST OF FIGURES
FIGURE NO. TITLE PAGE NO.
1-1. Lubrication Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-4
1-2. Serial Number Locations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-5
1-3. Torque Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-6
2-1. Barrel Support. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-6
2-2. Cap Screw Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-6
2-3. Rod Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-6
2-4. Tapered Bushing Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-6
2-5. Rod Seal Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-7
2-6. Poly-Pak Seal Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-8
2-7. Wiper Seal Installation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-8
2-8. Head Seal Kit Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-8
2-9. Piston Seal Kit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-8
2-10. Tapered Bushing Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-9
2-11. Rod Assembly Installation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-9
2-12. Steer Cylinder Assembly. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-10
2-13. Tilt Switch Leveling - Manual Adjustment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-12
2-14. Tilt Switch Leveling - Voltmeter Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-13
2-15. Valve Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-14
2-16. Drive Axle Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-16
2-17. Carrier Section. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-21
2-18. Ring Gear and Pinion Tooth Contact Pattern. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-22
2-19. Ring Gear Pattern Interpretation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-23
2-20. Brake Assembly. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-25
2-21. ADDCO Adjustments (Gasoline/Dual Fuel Engine) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-27
2-22. ADDCO Adjustments (Diesel Engine). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-28
2-23. Valve Driver Card. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-29
3-1. Electrical Schematic - Yanmar (Sheet of 1 of 2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-10
3-2. Electrical Schematic - Yanmar (Sheet of 2 of 2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-11
3-3. Electrical Schematic - Daihatsu (Sheet 1 of 2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-12
3-4. Electrical Schematic - Daihatsu (Sheet 2 of 2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-13
3-5. Hydraulic Schematic (Sheet 1 of 2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-14
3-6. Hydraulic Schematic (Sheet 2 of 2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-15
LIST OF TABLES
TABLE NO. TITLE PAGE NO.
1-1 Hydraulic Oil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-2
1-2 Lubrication Specifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-3
1-3 Cylinder Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-3
1-4 Major Component Weights. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-3
1-5 Critical Stability Weights . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-3
1-6 Lubrication Chart. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-4
2-1 Cylinder Component Torque Specifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-9
2-2 Holding Valve Torque Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-9
2-3 Preventive Maintenance and Safety Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-32
3-1 Elevation System Troubleshooting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-2
3-2 Chassis Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-4
3-3 Hydraulic System Troubleshooting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-7
3-4 Electrical System Troubleshooting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . .3-8

SECTION 1 - SPECIFICATIONS
3120791 – JLG Sizzor – 1-1
SECTION 1. SPECIFICATIONS
1.1 CAPACITIES
Hydraulic Oil Tank
15.0 gallons (56.8 liters)
Hydraulic System (Including Tank)
Approximately 18.0 gallons (68.1 liters)
Fuel Tank
7.8 gallons (29.5 liters)
Drive Axle
3 pints (6.4 liters)
1.2 COMPONENT DATA
Engine
Daihatsu Gasoline/LP
3 cylinder, liquid-cooled
21 horsepower @ 3,000 rpm
Idle - 1,500 rpm
Mid Engine - 2,000 rpm
High Engine - 3,000 rpm
Alternator - 14 Amp
Cooling System Capacity
Engine - 1.9 quarts (1.8 liters)
Crankcase Capacity - 3.2 quarts (3.0 liters)
Yanmar Diesel
3 cylinder, liquid-cooled
22 horsepower @ 3,000 rpm
Idle - 1,200 rpm
Mid Engine - 2,000 rpm
High Engine - 3,000 rpm
Alternator - 40 Amp
Cooling System Capacity
1.0 quarts (0.9 liters) - engine
Crankcase Capacity - 2.5 quarts (2.4 liters)
Drive Pump
Closed loop piston type
Output - 15 gpm (56.8 lpm) @ 3,000 rpm
Displacement - 1.16 in.3/rev. (19.0 cm3/rev.)
Lift/Steer Pump
Gear type
Output - 3.1 gpm (11.7 lpm) @ 3,000 rpm.
Displacement - 0.24 in.3/rev. (4.0 cm3/rev.).
Steer/Drive System
Steer (Front) Tires - Dico Multi-Trac C/S 26 x 12.00 - 12
NHS; 6 ply; inflate to 40 psi (2.8 bar).
Toe-In - Adjust to 1/4 inch (6.4 mm) overall.
Drive (Rear) Tires - Dico Tru-Power TL 26 x 12.00 - 12
NHS; 6 ply; inflate to 40 psi (2.8 bar).
Drive Brake - Mico hydraulic multi-disc.
Drive Motor - Eaton 2000 Series; 8.0 in.3/rev. (131 cm3/
rev.).
Drive Axle - Dana Model 44 rigid semi-float, no spin axle
assembly; 5.89 ratio; oil capacity - 3 pints (1.4 liters).
Hydraulic Filter - Inline
Return - Bypass Type
10 Microns Nominal
Platform Size
Standard - 54 in. x 88 in. (1.4 m x 2.2 m)
1.3 PERFORMANCE DATA
Travel Speed
Maximum Speed - 4.5 mph (7.2 kmh)
Elevated Speed - 0.7 mph (1.1 kmh)
Gradeability
35%
Turning Radius
Inside - 8 ft. 1 in. (2.5 m)
Outside - 15 ft. 4 in. (4.7 m)

SECTION 1 - SPECIFICATIONS
1-2 – JLG Sizzor – 3120791
Lift
Up - 34-42 seconds
Down - 31-39 seconds
Platform Capacity
Standard - 1,000 lb. (455 kg).
Manual Platform Extension Capacity
250 lb. (115 kg)
Machine Weight
Approximately 5,200 lb. (2359 kg)
Wheelbase
78.0 in. (2.0 m)
Machine Height (Platform Fully Elevated)
26 ft. (7.9 m)
Machine Height (Platform Lowered)
89.0 in. (2.3 m)
Platform Railing Height
39.5 in. (1.0 m)
Machine Length
105.0 in. (2.7 m)
Machine Width
69.0 in. (1.8 m)
Ground Clearance
5.5 in. (14.0 cm)
Maximum Tire Load
2,030 lb. (921 kg) @ 19 psi (1.3 bar)
1.4 TORQUE REQUIREMENTS
All wheel lug nuts should be torqued to 90 ft lb (122 Nm)
every 150 hours.
NOTE: When maintenance becomes necessary or a fas-
tener has loosened, refer to the Torque Chart Figure
7-1 to determine proper torque value.
1.5 LUBRICATION
Hydraulic Oil
NOTE: Hydraulic oils must have anti-wear qualities at least
to API Service Classification GL-3, and sufficient
chemical stability for mobile hydraulic system ser-
vice. JLG Industries recommends Mobilfluid 424
hydraulic oil, which has an SAE viscosity of 10W-30
and a viscosity index of 152.
When temperatures remain consistently below -20°
F (-7° C), an amount of no. 2 diesel fuel, not to
exceed 20% of system capacity, may be added to
the hydraulic oil reservoir. This diesel fuel will “thin”
the hydraulic oil for easier cold weather operation,
and will almost completely dissipate from the hydrau-
lic system over a several month period of time. When
cold weather is past, it may be necessary to drain
and refill the hydraulic system to rid the system of
any remaining diesel fuel.
Aside from JLG recommendations, it is not advisable
to mix oils of different brands or types, as they may
not contain the same required additives or be of
comparable viscosities. If use of hydraulic oil other
than Mobilfluid 424 is desired, contact JLG Indus-
tries for proper recommendations.
Table 1-1. Hydraulic Oil
HYDRAULICSYSTEMOPERATING
TEMPERATURERANGE SAEVISCOSITYGRADE
0to+23degreesF
(-18to-5degreesC) 10W
0to+210degreesF
(-18to+100degreesC) 10W-20,10W-30
+50to+210degreesF
(+10to+100degreesC) 20W-20

SECTION 1 - SPECIFICATIONS
3120791 – JLG Sizzor – 1-3
Lubrication Specifications
1.6 CYLINDER SPECIFICATIONS
NOTE: All dimensions are given in inches (in), with the met-
ric equivalent, centimeters (cm), given in parenthe-
ses.
1.7 PRESSURE SETTINGS
Main Relief - 2100 psi (145 bar)
Steer Relief - 1500 psi (103 bar)
Lift Up Relief - 2100 psi (145 bar)
Lift Down Relief - 900 psi (62 bar)
1.8 SERIAL NUMBER LOCATIONS
For machine identification, a serial number plate is affixed
to the machine. The plate is located on the rear center of
the machine frame, just below the middle step of the lad-
der. In addition, if the serial number plate is damaged or
missing, the machine serial number is stamped on the
right front frame rail, adjacent to the sizzor arms.
1.9 LIMIT SWITCHES
The machine is equipped with the following limit switches:
Tilt Alarm (Optional) - 5° - Illuminates a light on the plat-
form and sounds an alarm when the machine is 5° out of
level in any direction.
High Drive Cut-Out - High drive speed is cut out when the
platform is raised above the stowed position.
1.10 MAJOR COMPONENT WEIGHTS
1.11 CRITICAL STABILITY WEIGHTS
DO NOT REPLACE ITEMS CRITICAL TO STABILITY, SUCH AS
ENGINES, AXLES OR TIRES, WITH ITEMS OF DIFFERENT
WEIGHT OR SPECIFICATION. DO NOT MODIFY UNIT IN ANY WAY
TO AFFECT STABILITY.
Table 1-2. Lubrication Specifications
KEY SPECIFICATIONS
MPG MultipurposeGreasehavingaminimumdripping
pointof350degressF.Excellentwaterresistance
andadhesivequalities,andbeingofextremepres-
suretype.(TimkenOK40poundsminimum.)
EPGL ExtremePressureGearLube(oil)meetingAPIser-
viceclassificationGL-5orMIL-SpecMIL-L-2105.
EO Engine(crankcase)Oil.Gas-APISF/SGclass,MIL-
L-2104.Diesel-APICC/CDclass,MIL-L-2104B/
MIL-L-2104C.
HO HydraulicOil.APIserviceclassificationGL-3,e.g.
Mobil424.
Table 1-3. Cylinder Specifications
Description Bore Stroke Rod Dia.
Lift Cylinder 4.00
(10.2) 39.75 (101.0) 2.50 (6.4)
SteerCylinder
(DoubleRrod) 2.00 (5.1) 2.69 (6.83) 1.25 (3.18)
Table 1-4. Major Component Weights
Component lb kg
Platform 382 173
ManualPlatformExtension 221 100
ArmAssembly(IncludesLiftCylinder) 1618 734
Chassis-w/StandardTires 2979 1351
Table 1-5. Critical Stability Weights
Component lb kg
TireandWheelAssembly-Std (each) 50 23
DaihatsuGasoline/LPEngine 132 60
YanmarDieselEngine 183 81
DanaDriveAxle 130 59

SECTION 1 - SPECIFICATIONS
1-4 – JLG Sizzor – 3120791
Figure 1-1. Lubrication Diagram
Table 1-6. Lubrication Chart
INDEX
NO COMPONENT NUMBER/TYPE LUBE POINTS LUBE METHODS INTERVAL
HOURS
1 WheelBearings 2- FrontWheels MPG-repack 1200
2 HydraulicOil FillCap/DrainPlug HO-CheckHOLevel
HO-ChangeHO Daily/1200
3 HydraulicReturnFilter N/A N/A 50/300
4 ChargePumpFilter N/A N/A 50/300
5 Crankcase-VanguardGasoline/LP
Engine FillCap/DrainPlug EO-CheckEOLevel EO-ChangeEO Daily/50/300
6 Crankcase-YanmarDieselEngine FillCap/DrainPlug EO-CheckEOLevel
EO-ChangeEO Daily/50/300
7 RearAxle FillCap/DrainPlug EPGL-Check EPGLLevel
EPGL-Change EPGL 150/1200
KEY TO LUBRICANTS:
EO - Engine Oil
EPGL - Extreme Pressure Gear Lubricant
HO - Hydraulic Oil - Mobilfluid 424
MPG - Multi-purpose Grease
TO AVOID PERSONAL INJURY, USE SAFETY PROP FOR ALL
MAINTENANCE REQUIREING PLATFORM TO BE ELEVATED.
NOTE: 1. Be sure to lubricate like items on each side.
2. Recommended lubricating intervals are based
on maching operations under normal conditions.
For machines used in multi-shift operations and/or
exposed to hostile environments or conditions,
lubrication frequencies must be increased accord-
ingly.
3. Operate hydraulic functions through one com-
plete cycle before checking hydraulic oil level in
tank. Oil should be visible in ADD sight window on
hydraulic tank. If oil is not visible, add oil until oil is
visible in both ADD and FULL sight windows on
tank. Do not overfill tank.

SECTION 1 - SPECIFICATIONS
3120791 – JLG Sizzor – 1-5
Figure 1-2. Serial Number Locations

SECTION 1 - SPECIFICATIONS
1-6 – JLG Sizzor – 3120791
Figure 1-3. Torque Chart

SECTION 2 - PROCEDURES
3120791 – JLG Sizzor – 2-1
SECTION 2. PROCEDURES
2.1 GENERAL
This section provides information necessary to perform
maintenance on the scissor lift. Descriptions, techniques
and specific procedures are designed to provide the saf-
est and most efficient maintenance for use by personnel
responsible for ensuring the correct installation and oper-
ation of machine components and systems.
WHEN AN ABNORMAL CONDITION IS NOTED AND PROCEDURES
CONTAINED HEREIN DO NOT SPECIFICALLY RELATE TO THE
NOTED IRREGULARITY, WORK SHOULD BE STOPPED AND
TECHNICALLY QUALIFIED GUIDANCE OBTAINED BEFORE WORK
IS RESUMED.
The maintenance procedures included consist of servic-
ing and component removal and installation, disassembly
and assembly, inspection, lubrication and cleaning. Infor-
mation on any special tools or test equipment is also pro-
vided where applicable.
2.2 SERVICING AND MAINTENANCE
GUIDELINES
General
The following information is provided to assist you in the
use and application of servicing and maintenance proce-
dures contained in this chapter.
Safety and Workmanship
Your safety, and that of others, is the first consideration
when engaging in the maintenance of equipment. Always
be conscious of weight. Never attempt to move heavy
parts without the aid of a mechanical device. Do not allow
heavy objects to rest in an unstable position. When raising
a portion of the equipment, ensure that adequate support
is provided.
Cleanliness
1. The most important single item in preserving the
long service life of a machine is to keep dirt and for-
eign materials out of the vital components. Precau-
tions have been taken to safeguard against this.
Shields, covers, seals, and filters are provided to
keep air, fuel, and oil supplies clean; however, these
items must be maintained on a scheduled basis in
order to function properly.
2. At any time when air, fuel, or oil lines are discon-
nected, clear adjacent areas as well as the openings
and fittings themselves. As soon as a line or compo-
nent is disconnected, cap or cover all openings to
prevent entry of foreign matter.
3. Clean and inspect all parts during servicing or main-
tenance, and assure that all passages and openings
are unobstructed. Cover all parts to keep them
clean. Be sure all parts are clean before they are
installed. New parts should remain in their contain-
ers until they are ready to be used.
Components Removal and Installation
4. Use adjustable lifting devices, whenever possible, if
mechanical assistance is required. All slings (chains,
cables, etc.) should be parallel to each other and as
near perpendicular as possible to top of part being
lifted.
5. Should it be necessary to remove a component on
an angle, keep in mind that the capacity of an eye-
bolt or similar bracket lessens, as the angle between
the supporting structure and the component
becomes less than 90°.
6. If a part resists removal, check to see whether all
nuts, bolts, cables, brackets, wiring, etc., have been
removed and that no adjacent parts are interfering.
Component Disassembly and Reassembly
When disassembling or reassembling a component, com-
plete the procedural steps in sequence. Do not partially
disassemble or assemble one part, then start on another.
Always recheck your work to assure that nothing has been
overlooked. Do not make any adjustments, other than
those recommended, without obtaining proper approval.
Pressure-Fit Parts
When assembling pressure-fit parts, use an “anti-seize” or
molybdenum disulfide base compound to lubricate the
mating surface.
Bearings
1. When a bearing is removed, cover it to keep out dirt
and abrasives. Clean bearings in nonflammable
cleaning solvent and allow to drip dry. Compressed
air can be used but do not spin the bearing.
2. Discard bearings if the races and balls (or rollers)
are pitted, scored, or burned.
3. If a bearing is found to be serviceable, apply a light
coat of oil and wrap it in clean (waxed) paper. Do not
unwrap reusable or new bearings until they are
ready to install.

SECTION 2 - PROCEDURES
2-2 – JLG Sizzor – 3120791
4. Lubricate new or used serviceable bearings before
installation. When pressing a bearing into a retainer
or bore, apply pressure to the outer race. If the bear-
ing is to be installed ona shaft, apply pressure to the
inner race.
Gaskets
Check that holes in gaskets align with openings in the
mating parts. If it becomes necessary to hand-fabricate a
gasket, use gasket material or stock of equivalent material
and thickness. Be sure to cut holes in the right location, as
blank gaskets can cause serious system damage.
Bolt Usage and Torque Application
1. Use bolts of proper length. A bolt which is too long
will bottom before the head is tight against its related
part. If a bolt is too short, there will not be enough
thread area to engage and hold the part properly.
When replacing bolts, use only those having the
same specifications of the original, or one which is
equivalent.
2. Unless specific torque requirements are given within
the text, standard torque values should be used on
heat-treated bolts, studs, and steel nuts, in accor-
dance with recommended shop practices.
Hydraulic Lines and Electrical Wiring
Clearly mark or tag hydraulic lines and electrical wiring, as
well as their receptacles, when disconnecting or removing
them from the unit. This will assure that they are correctly
reinstalled.
Hydraulic System
1. Keep the system clean. If evidence of metal or rub-
ber particles is found in the hydraulic system, drain
and flush the entire system.
2. Disassemble and reassemble parts on clean work
surface. Clean all metal parts with non-flammable
cleaning solvent. Lubricate components, as
required, to aid assembly.
Lubrication
Service applicable components with the amount, type,
and grade of lubricant recommended in this manual, at
the specified intervals. When recommended lubricants are
not available, consult your local supplier for an equivalent
that meets or exceeds the specifications listed.
Batteries
Clean batteries, using a non-metallic brush and a solution
of baking soda and water. Rinse with clean water. After
cleaning, thoroughly dry batteries and coat terminals with
an anti-corrosion compound.
Lubrication and Servicing
Components and assemblies requiring lubrication and
servicing are shown in Section 1.
2.3 LUBRICATION INFORMATION
Hydraulic System
1. The primary enemy of a hydraulic system is contam-
ination. Contaminants enter the system by various
means, e.g., using inadequate hydraulic oil, allowing
moisture, grease, filings, sealing components, sand,
etc., to enter when performing maintenance, or by
permitting the pump to cavitate due to insufficient
system warm-up or leaks in the pump supply (suc-
tion) lines.
2. The design and manufacturing tolerances of the
component working parts are very close, therefore,
even the smallest amount of dirt or foreign matter
entering a system can cause wear or damage to the
components and generally results in faulty opera-
tion. Every precaution must be taken to keep
hydraulic oil clean, including reserve oil in storage.
Hydraulic system filters should be checked,
cleaned, and/or replaced as necessary, at the speci-
fied intervals required in the Lubrication Chart in
Section 1 and the Preventive Maintenance and
Inspection Chart in this section. Always examine fil-
ters for evidence of metal particles.
3. Cloudy oils indicate a high moisture content which
permits organic growth, resulting in oxidation or cor-
rosion. If this condition occurs, the system must be
drained, flushed, and refilled with clean oil.
4. It is not advisable to mix oils of different brands or
types, except as recommended, as they may not
contain the same required additives or be of compa-
rable viscosities. Good grade mineral oils, with vis-
cosities suited to the ambient temperatures in which
the machine is operating, are recommended for use.
NOTE: Metal particles may appear in the oil or filters of new
machines due to the wear-in of meshing compo-
nents.
Hydraulic Oil
1. Refer to Section1 for recommendations for viscosity
ranges.
2. JLG recommends Mobilfluid 424, which has an SAE
viscosity of 10W-30 and a viscosity index of 152.

SECTION 2 - PROCEDURES
3120791 – JLG Sizzor – 2-3
NOTE: Start-up of hydraulic system with oil temperatures
below -15° F (-26° C). is not recommended. If it is
necessary to start the system in a sub-zero environ-
ment, it will be necessary to heat the oil with a low
density, 100VAC heater to a minimum temperature of
-15° F (-26 ° C).
3. The only exception to the above is to drain and fill
the system with Mobil DTE 11 oil or its equivalent.
This will allow start up at temperatures down to -20 °
F (-29° C). However, use of this oil will give poor per-
formance at temperatures above 120° F (49° C). Sys-
tems using DTE 11 oil should not be operated at
temperatures above 200°F (94°C). under any condi-
tion.
Changing Hydraulic Oil
1. Use of any of the recommended crankcase or
hydraulic oils eliminates the need for changing the
oil on a regular basis. However, filter elements must
be changed after the first 50 hours of operation and
every 300 hours thereafter. If it is necessary to
change the oil, use only those oils meeting or
exceeding the specifications appearing in this man-
ual. If unable to obtain the same type of oil supplied
with the machine, consult local supplier for assis-
tance in selecting the proper equivalent. Avoid mix-
ing petroleum and synthetic base oils. JLG
Industries recommends changing the hydraulic oil
every two years.
2. Use every precaution to keep the hydraulic oil clean.
If the oil must be poured from the original container
into another, be sure to clean all possible contami-
nants from the service container. Always clean the
mesh element of the filter and replace the cartridge
any time the system oil is changed.
3. While the unit is shut down, a good preventive main-
tenance measure is to make a thorough inspection
of all hydraulic components, lines, fittings, etc., as
well as a functional check of each system, before
placing the machine back in service.
Lubrication Specifications
Specified lubricants, as recommended by the component
manufacturers, are always the best choice, however,
multi-purpose greases usually have the qualities which
meet a variety of single purpose grease requirements.
Should any question arise regarding the use of greases in
maintenance stock, consult your local supplier for evalua-
tion. Refer to Table 7-1 for an explanation of the lubricant
key designations appearing in the Lubrication Chart.
2.4 CYLINDERS - THEORY OF OPERATION
Cylinders are of the double acting type. The Lift and Steer
systems incorporate double acting cylinders. A double
acting cylinder is one that requires oil flow to operate the
cylinder rod in both directions. Directing oil (by actuating
the corresponding control valve to the piston side of the
cylinder) forces the piston to travel toward the rod end of
the barrel, extending the cylinder rod (piston attached to
rod). When the oil flow is stopped, movement of the rod
will stop. By directing oil to the rod side of the cylinder, the
piston will be forced in the opposite direction and the cyl-
inder rod will retract.
A holding valve is used in the Lift circuit to prevent retrac-
tion of the cylinder rod should a hydraulic line rupture or a
leak develop between the cylinder and its related control
valve.
2.5 VALVES - THEORY OF OPERATION
Solenoid Control Valves (Bang-Bang)
Control valves used are four-way three-position solenoid
valves of the sliding spool design. When a circuit is acti-
vated and the control valve solenoid energizes, the spool
is shifted and the corresponding work port opens to per-
mit oil flow to the component in the selected circuit, with
the opposite work port opening to reservoir. Once the cir-
cuit is deactivated (control returned to neutral), the valve
spool returns to neutral (center) and oil flow is then
directed through the valve body and returns to reservoir. A
typical control valve consists of the valve body, sliding
spool, and two solenoid assemblies. The spool is
machine fitted in the bore of the valve body. Lands on the
spool divide the bore into various chambers, which, when
the spool is shifted, align with corresponding ports in the
valve body open to common flow. At the same time other
ports would be blocked to flow. The spool is spring-
loaded to center position, therefore when the control is
released, the spool automatically returns to neutral, pro-
hibiting any flow through the circuit.
Proportional Control Valves
The proportional control valves provide a power output
matching that required by the load. A small line connected
to a load sensing port feeds load pressure back to a
sequence valve. The sequence valve senses the differ-
ence between the load and pump outlet pressure, and
varies the pump displacement to keep the difference con-
stant. This differential pressure is applied across the
valve’s meter-in spool, with the effect that pump flow is
determined by the degree of spool opening, independent
of load pressure. Return lines are connected together,
simplifying routing of return flow and to help reduce cavi-
tation. Load sensing lines connect through shuttle valves
to feed the highest load signal back to the sequence

SECTION 2 - PROCEDURES
2-4 – JLG Sizzor – 3120791
valve. Integral actuator port relief valves, anti-cavitation
check valves, and load check valves are standard.
Relief Valves
Main relief valves are installed at various points within the
hydraulic system to protect associated systems and com-
ponents against excessive pressure. Excessive pressure
can be developed when a cylinder reaches its limit of
travel and the flow of pressurized fluid continues from the
system control. The relief valve provides an alternate path
for the continuing flow from the pump, thus preventing
rupture of the cylinder, hydraulic line or fitting. Complete
failure of the system pump is also avoided by relieving cir-
cuit pressure. The relief valve is installed in the circuit
between the pump outlet (pressure line) and the cylinder
of the circuit, generally as an integral part of the system
valve bank. Relief pressures are set slightly higher than
the load requirement, with the valve diverting excess
pump delivery back to the reservoir when operating pres-
sure of the component is reached.
Crossover Relief Valves
Crossover relief valves are used in circuits where the actu-
ator requires an operating pressure lower than that sup-
plied to the system. When the circuit is activated and the
required pressure at the actuator is developed, the cross-
over relief diverts excess pump flow to the reservoir. Indi-
vidual, integral reliefs are provided for each side of the
circuit.
2.6 COMPONENT FUNCTIONAL
DESCRIPTION
Hydraulic Pump
The machine is equipped with two hydraulic pumps, a
function pump and a drive pump. The function pump is a
single-section gear pump that controls the lift and steer
functions and provides an output of 3.1 gpm (11.7 lpm).
The drive pump is a single-section piston pump that con-
trols the drive function and provides an output of 15 gpm
(56.8 lpm).
Lift Cylinder Counterbalance/Manual
Descent Valve
The lift cylinder counterbalance/manual descent valve is
located on top of the lift cylinder. The counterbalance
valve is used to hold the platform in place when raised. A
cable is connected to the valve which, when pulled, manu-
ally opens the lift down port and allows the platform to be
lowered in the event hydraulic power is lost.
2.7 WEAR PADS
Sliding Pads
The original thickness of the sliding pads is 2 inches (51
mm). Replace sliding pads when worn to 1.875 inches (48
mm).
2.8 CYLINDER CHECKING PROCEDURES
NOTE: Cylinder checks must be performed any time a cylin-
der component is replaced or when improper system
operation is suspected.
Cylinder w/o Counterbalance Valves - Steer
Cylinder
OPERATE FUNCTIONS FROM GROUND CONTROL STATION
ONLY.
DO NOT FULLY EXTEND CYLINDER TO END OF STROKE.
RETRACT CYLINDER SLIGHTLY TO AVOID TRAPPING PRES-
SURE.
1. Using all applicable safety precautions, activate
motor and fully extend cylinder to be checked. Shut
down motor.
2. Carefully disconnect hydraulic hose from retract port
of cylinder. There will be initial weeping of hydraulic
fluid which can be caught in a suitable container.
After the initial discharge, there should be no further
leakage from the retract port.
3. Activate motor and activate cylinder extend function.
Check retract port for leakage.
4. If cylinder leakage is 6-8 drops per minute or more,
piston seals are defective and must be replaced. If
cylinder retract port leakage is less than 6-8 drops
per minute, carefully reconnect hose to retract port
and retract cylinder.
5. With cylinder fully retracted, shut down motor and
carefully disconnect hydraulic hose from cylinder
extend port.
6. Activate motor and activate cylinder retract function.
Check extend port for leakage.
7. If cylinder leakage is 6-8 drops per minute or more,
piston seals are defective and must be replaced. If
extend port leakage is less than 6-8 drops per
minute, carefully reconnect hose to extend port,
then activate cylinder through one complete cycle
and check for leaks.

SECTION 2 - PROCEDURES
3120791 – JLG Sizzor – 2-5
Cylinders w/Single Counterbalance Valves -
Lift Cylinder
OPERATE ALL FUNCTIONS FROM GROUND CONTROL STATION
ONLY.
1. Using all applicable safety precautions, activate
hydraulic system.
WHEN WORKING ON THE LIFT CYLINDER, RAISE THE PLAT-
FORM COMPLETELY AND SUPPORT THE PLATFORM USING A
SUITABLE OVERHEAD LIFTING DEVICE.
DO NOT FULLY EXTEND LIFT CYLINDER TO END OF STROKE.
RETRACT CYLINDER SLIGHTLY TO AVOID TRAPPING PRES-
SURE.
2. Raise platform completely then retract cylinder
slightly to avoid trapping pressure. Place a suitable
overhead lifting device approximately 1 inch (2.5
cm) below the platform.
3. Shut down hydraulic system and allow machine to
sit for 10-15 minutes. Carefully remove hydraulic
hoses from cylinder port block.
4. There will be initial weeping of hydraulic fluid, which
can be caught in a suitable container. After the initial
discharge, there should not be any further leakage
from the ports. If leakage continues at a rate of 6-8
drops per minute or more, the counterbalance valve
is defective and must be replaced.
5. If no repairs are necessary or when repairs have
been made, carefully reconnect hydraulic hoses to
the appropriate ports.
6. Remove lifting device from platform, activate hydrau-
lic system and run cylinder through one complete
cycle to check for leaks.
2.9 LIFT CYLINDER REMOVAL AND
INSTALLATION
Removal
1. Place the machine on a flat and level surface. Start
the motor and raise the platform. Shut down the
engine and attach a suitable lifting device to the plat-
form.
2. Remove the bolt and locknut securing the cylinder
rod attach pin to the upper inner arm assembly.
Using a suitable brass drift, drive out the rod end
attach pin from the arm assembly.
3. Retract the lift cylinder rod completely.
4. Tag and disconnect the hydraulic lines, then cap the
lift cylinder hydraulic lines and ports.
5. Remove the bolt and locknut securing the barrel end
attach pin to the lower arm assembly. Using a suit-
able brass drift, drive out the barrel end attach pin
from the arm assembly.
6. Carefully remove the cylinder from the scissor lift
and place in a suitable work area.
Installation
1. Install lift cylinder in place using suitable slings,
aligning barrel end attach pin mounting holes on
lower arm assembly.
2. Using a suitable drift, drive the barrel end attach pin
through the mounting holes in the lift cylinder and
the lower arm assembly. Secure in place with the
bolt and locknut.
3. Remove cylinder port plugs and hydraulic line caps
and correctly attach lines to cylinder ports.
4. Extend the cylinder rod until the attach pin hole
aligns with those in the upper arm assembly. Using a
suitable drift, drive the cylinder rod attach pin
through the aligned holes, taking care to align the
pin retaining hole with the hole in arm assembly.
Secure the pin in place with the bolt and locknut.
5. Lower platform to stowed position and shut down
motor. Check hydraulic fluid level and adjust accord-
ingly.
2.10 LIFT CYLINDER REPAIR
Disassembly
DISASSEMBLY OF THE CYLINDER SHOULD BE PERFORMED ON
A CLEAN WORK SURFACE IN A DIRT FREE WORK AREA.
1. Connect a suitable auxiliary hydraulic power source
to the cylinder port block fitting.
DO NOT FULLY EXTEND CYLINDER TO END OF STROKE.
RETRACT CYLINDER SLIGHTLY TO AVOID TRAPPING PRES-
SURE.
2. Operate the hydraulic power source and extend the
cylinder. Shut down and disconnect the power
source. Adequately support the cylinder rod, if nec-
essary.

SECTION 2 - PROCEDURES
2-6 – JLG Sizzor – 3120791
3. If applicable, remove the cartridge-type holding
valve and fittings from the cylinder port block. Dis-
card o-rings.
4. Place the cylinder barrel into a suitable holding fix-
ture.
5. To aid in realignment, mark cylinder head and barrel
with a center punch. Using an allen wrench, loosen
the eight (8) cylinder head retainer cap screws and
remove cap screws from cylinder barrel.
6. If applicable, using a suitable spanner wrench,
loosen the spanner nut retainer and remove the
spanner nut from the cylinder barrel.
7. Attach a suitable pulling device to the cylinder rod
port block or cylinder rod end, as applicable.
EXTREME CARE SHOULD BE TAKEN WHEN REMOVING THE CYL-
INDER ROD, HEAD, AND PISTON. AVOID PULLING THE ROD OFF-
CENTER, WHICH COULD CAUSE DAMAGE TO THE PISTON AND
CYLINDER BARREL SURFACES.
8. With the barrel clamped securely, apply pressure to
the rod pulling device and carefully withdraw the
complete rod assembly from the cylinder barrel.
9. Using suitable protection, clamp the cylinder rod in
a vise or similar holding fixture as close to the piston
as possible.
10. If applicable, loosen and remove the nut which
attaches the piston to the rod, then remove the pis-
ton from the rod.
11. If applicable, loosen and remove the cap screw(s)
securing the tapered bushing to the piston.
12. Insert the capscrew(s) in the threaded holes in the
outer piece of the tapered bushing. Progressively
tighten the cap screw(s) until the bushing is loose
on the piston, then remove the bushing from the pis-
ton.
13. Screw the piston counter-clockwise, by hand, and
remove the piston from the cylinder rod.
14. Remove and discard the piston o-rings, back-up
rings, guidelock rings and hydrolock seals.
Figure 2-1. Barrel Support
Figure 2-2. Cap Screw Removal
Figure 2-3. Rod Support
Figure 2-4. Tapered Bushing Removal

SECTION 2 - PROCEDURES
3120791 – JLG Sizzor – 2-7
15. If applicable, remove the piston spacer from the rod.
16. Remove the rod from the holding fixture. Remove
the cylinder head and retainer plate from the rod.
Cleaning and Inspection
1. Clean all parts thoroughly in an approved cleaning
solvent.
2. Inspect the cylinder rod for scoring, tapering, ovality,
or other damage. If necessary, dress rod with
Scotch Brite or equivalent. Replace rod if necessary.
3. Inspect threaded portion of rod for damage. Dress
threads as necessary.
4. Inspect inner surface of cylinder barrel tube for scor-
ing or other damage. Check inside diameter for
tapering or ovality. Replace if necessary.
5. Inspect threaded portion of barrel for damage. Dress
threads as necessary.
6. Inspect piston surface for damage and scoring and
for distortion. Dress piston surface or replace piston
as necessary.
7. Inspect threaded portion of piston for damage.
dress threads as necessary.
8. Inspect seal and o-ring grooves in piston for burrs
and sharp edges. Dress applicable surfaces as nec-
essary.
9. Inspect cylinder head inside diameter for scoring or
other damage and for ovality and tapering. Replace
as necessary.
10. Inspect threaded portion of head for damage. Dress
threads as necessary.
11. Inspect seal and o-ring grooves in head for burrs
and sharp edges. Dress applicable surfaces as nec-
essary.
12. Inspect cylinder head outside diameter for scoring
or other damage and ovality and tapering. Replace
as necessary.
13. If applicable, inspect rod and barrel bearings for
signs of correct lubrication and excessive wear. If
necessary, replace bearings as follows:
a. Thoroughly clean steel bushing hole of burrs,
dirt, etc. to facilitate bearing installation.
b. Inspect steel bushing for wear or other damage.
If steel bushing is worn or damaged, rod or bar-
rel (as applicable) must be replaced.
c. Lubricate inside of steel bushing with WD-40
prior to bearing installation.
d. Using arbor of the correct size, carefully press
the bearing into the steel bushing.
NOTE: Install the cylinder pin into the Gar-Max bearing dry.
Lubrication is not required with chrome pins and
bearings.
14. Inspect travel limiting collar or spacer for burrs and
sharp edges. If necessary, dress inside diameter
surface with Scotch Brite or equivalent.
15. If applicable, inspect port block fittings and holding
valve. Replace as necessary.
16. Inspect the oil ports for blockage or the presence of
dirt or other foreign material. Repair as necessary.
17. If applicable, inspect piston rings for cracks or other
damage. Replace as necessary.
Assembly
NOTE: Prior to cylinder assembly, ensure that the proper
cylinder seal kit is used.
Apply a light film of hydraulic oil to all components
prior to assembly.
1. Using a special tool, pictured in the following illustra-
tion, install a new rod seal into the applicable cylin-
der head gland groove. Refer to the following
illustration for the proper tool size.
WHEN INSTALLING NEW “POLY-PAK” TYPE PISTON SEALS,
ENSURE SEALS ARE INSTALLED PROPERLY. REFER TO FIGURE
2-9., PISTON SEAL KIT FOR CORRECT SEAL ORIENTATION.
IMPROPER SEAL INSTALLATION COULD RESULT IN CYLINDER
LEAKAGE AND IMPROPER CYLINDER OPERATION.
Figure 2-5. Rod Seal Installation

SECTION 2 - PROCEDURES
2-8 – JLG Sizzor – 3120791
2. Using a soft mallet, tap a new wiper seal into the
applicable cylinder head gland groove. Install a new
wear ring into the applicable head gland groove.
3. Place a new o-ring and back-up seal in the applica-
ble outside diameter groove of the cylinder head as
shown in the following illustration.
4. Install a washer ring onto the rod, then carefully
install the head gland on the rod, ensuring that the
wiper and rod seals are not damaged or dislodged.
Push the head along the rod to the rod end, as
applicable.
5. Carefully slide the piston spacer onto the rod.
6. If applicable, correctly place a new o-ring and back-
up rings in the inner piston diameter groove.
7. Using suitable protection, clamp the cylinder rod in
a vise or similar holding fixture as close to the piston
as possible.
8. Carefully thread the piston on the cylinder rod hand
tight, ensuring that the o-ring and back-up rings are
not damaged or dislodged.
9. Thread the piston onto the rod until it abuts the
spacer end and install the tapered bushing.
NOTE: When installing the tapered bushing, the piston and
mating end of the rod must be free of oil.
WHEN REBUILDING THE LIFT CYLINDER, APPLY LOCTITE #242
TO TAPERED BUSHING BOLTS, THEN TIGHTEN BOLTS
SECURELY. REFER TO TABLE 2-1, CYLINDER COMPONENT
TORQUE SPECIFICATIONS FOR PROPER BOLT TORQUE VAL-
UES.
Figure 2-6. Poly-Pak Seal Installation
Figure 2-7. Wiper Seal Installation
Figure 2-8. Head Seal Kit Installation
Figure 2-9. Piston Seal Kit