Cat Lift Trucks. For use with K21/K25 and S4S Engine Service Manuals (2007)

STEERING SYSTEM

Structure and Function

Steering System

Main Components

1 Hydraulic tank

4 Steering valve

2 Hydraulic pump (Gear pump)

5 Steering wheel

section of hydraulic control valve

6 Steering cylinder

(Including flow priority valve)

The steering system of this lift truck is full hydraulic.

The oil delivered from the Gerotor is directed to the left

The oil drawn by hydraulic

2 from hydraulic tank

or right chamber of steering cylinder through the L or

1 enters the inlet section of the hydraulic control valve

port, applying a pressure to the cylinder rod.

3 through the P port. There is built-in flow priority

Simultaneously, the spool-and-sleeve valve in the

valve in the inlet section. The function of the flow

steering valve 4 opens the return oil passage from the

priority valve is to deliver pressure oil preferentially to

chamber of the steering cylinder to the hydraulic tank

steering valve 4. From the PF port, the oil flows to the

1. (The return oil goes through the steering valve's

P port of the steering valve.

port and then the hydraulic control valve 3 to the

hydraulic tank 1 .)

When the steering wheel is not turned (in the

ahead position), the oil flows through the steering

Two actions of the steering cylinder piston, each of

valve's T port to the

port in the hydraulic control

which supplies and returns pressure oil, respectively,

valve's inlet section and then returns to hydraulic tank

extend the cylinder rod to the right or left. These

actions turn the knuckle via the tie rod, steering rear

wheels.

When the steering wheel is turned, the oil from the

port enters the "Gerotor" passing through the P port

For the priority valve and the steering cylinder, refer to

and spool-and-sleeve valve in the steering valve 4.

"GROUP

HYDRAULIC SYSTEM" and "GROUP 8

(The Gerotor is a small trochoid

capable of

REAR AXLE," respectively.

delivering oil at a rate proportional to the number of

turns in which the steering wheel is turned.)

SYSTEM

Steering Gear

c: Metering pump inlets

f: Metering pump outlets

1 Spool

7 Drive shaft

A: Control section

2 Sleeve

8 Centering spring

B: Metering section

3 Outlet port (port T)

9 Pin

port (port P)

10 Left turn port (port L)

5 Rotor

11 Right turn port (port R)

6 Rotor ring

12 Housing

The steering valve consists of two sections: control

When the operator turns the steering wheel clockwise,

section A and metering section B.

the passage in the steering valve opens, allowing

pressure oil to flow through inlet port 4 into areas a, b,

Control section A includes spool

sleeve 2, and

and

housing 1 2 , constituting a rotary type directional

control valve. Spool 1 is spline-coupled to the steering

As rotor 5 turns together with the steering wheel, the oil

shaft. When spool 1 is turned, sleeve 2 rotates, opening

in areas d , e, and f is forced into the steering cylinder

the following passages to form a hydraulic circuit:

through right turn port 1 1 . When the steering wheel is

turned counterclockwise, oil flows in the direction

(1) A passage that allows oil to flow from inlet port 4

reverse to the above, entering the steering cylinder

to metering section

through left turn port 1 0.

(2) A passage that allows oil to flow from metering

Since the pressure oil from port 4 applies rotating force

section to port or

operator's effort on the steering wheel is

to rotor 5,

(3) A passage that allows the return oil from the

reduced.

steering cylinder to port T

Check valve 1 3 is normally pushed to the left direction

Metering section B is a trochoid-gear type, small

by pressure oil in the inlet port, blocking the bypass

hydraulic pump called "Gerotor" consisting of rotor

passage. When oil supply from the PF port of the

ring 6 and rotor 5.Spool 1 and rotor 5 are connected to

hydraulic valve stops for any reason, the bypass

each other with drive shaft 7. The rotor, therefore,

passage opens, allowing oil from

hydraulic tank to

turns in the same direction and at the same speed as the

flow to the metering section B. When the operator

steering wheel.

turns the steering wheel, the metering section acts as a

When the operator does not turn the steering wheel, the

complete manually-operated pump, causing oil to flow

oil flows from the port to port and

returns to

to the steering cylinder.

the hydraulic tank. The oil does not flow to the

metering section as it is blocked by the spool 1 and

sleeve 2.

10-2

STEERING SYSTEM

Steering Column

Column position when steering column

is tilted fully forward

Column position when lock is

Column neutral tilt position

inclination of 30 degrees to vertical line)

Column position when steering column is

tilted fully rearward

Steering column

mounting plate A

Bolt

When the tilt lever 3 is turned counterclockwise,

the plates A and are fixed between the bolt and

Main components

Steering column

4 Column lock lever

2 Bracket (secured to truck body)

3 Tilt lock lever

The steering column is tilt adjustable in the range of 5

degrees forward and 7 degrees rearward as shown in the

illustration.

For adjustment, lock the column lock lever 4 and then,

loosen the tilt lock lever 3 by turning it clockwise. Then,

tilt the steering column 1 to an adequate angle and turn the

tilt lock lever counterclockwise (pulling up) to lock.

The role of the column lock lever is to tilt the entire column

forward by a large amount for the convenience of getting

on and off, and of maintenance work. Push down the lock

lever to disengage the lock lever 4 from the lock pin 6 and

to tilt the steering column forward.

STEERING SYSTEM

Disassembly and Reassembly

Disassembly and Reassembly of Piping

Main parts or devices

1 Steering valve

5 Hose and pipe (steering valve T port T2

2 Hydraulic control valve (The illustration shows

MC valve.)

6 Hose (steering valve L port

steering

3 Steering cylinder

cylinder)

4 Hose (PF port steering valve P port)

7 Hose (steering valve R port

steering

cylinder)

Suggestions for disassembly and reassembly

(1) The most important point in maintenance of the

(4) When removing or installing hoses, use a double

hydraulic system is to perform work in a clean

spanner as needed to prevent excessive force from

place and never allow abrasive foreign substance to

being applied to the matching fittings.

enter the system.

(5) Bleed air after reassembly. Air bleeding method is

(2) O-rings must be replaced, once disturbed.

as follows.

(3) Hoses (especially high-pressure section) of the

(a) Raise the rear tires by placing jack stands under

steering system are safety related parts. These

the truck body.

specially designed parts need to be replaced at

(b) While changing the engine revolution by

specific periods, regardless of the presence or

depressing the accelerator pedal, turn the

absence of damage. For replacement interval,

steering wheel lock-to-lock and relieve

follow the "Operation Maintenance

pressure to bleed air.

STEERING SYSTEM

Removal and installation of Steering Wheel and Steering Valve

Disassembly sequence

Tightening torque:

52.6 to 65.3

Steering wheel

(5.36 to 6.48

2 Nut

to 46.8

3 Spring washer

4 Cover

5 Steering valve mounting bolt

6 Steering valve

7 Steering column assembly

mounting bolt

8 Steering column assembly

Tightening torque:

to 35

9.9 to 25.8

5 Tightening torque:

21 to 29

(2.1 to 3.0

5.5 to 21.4

Steering wheel

bolt

Removal

(1 ) Remove the horn button.

(2)

the steering wheel nut 2 and then, remove the

91268

10600

steering wheel 1 using a wheel puller.

Special tool needed

Wheel puller

91268 - 10600

209708

Wheel puller setting

When removing the steering wheel, do not tap

the top end of the steering shaft.

STEERING SYSTEM

Steering wheel

Horn switch contact

Installation

Install in the following sequence.

(1) Place the projection (a) on the steering sensor of

combination switch at the front as shown in the

illustration.

(2) Apply a light coating of grease to a sliding area of the

Projections form an

horn contact under the steering wheel boss.

isosceles triangle.

(3) Reassemble the steering wheel in a straight-ahead

position. (The projections of the combination switch fit

Combination switch

into the pits on the steering wheel.) Completely fit the

projections into the pits by turning the steering wheel

Forward

in the right and left directions several times.

(4) Before tightening the steering wheel nut, check that

automatic return of the combination switch functions.

(5) If automatic return does not function, repeat the

sequence (3) and (4) above.

(6) Tighten the steering wheel nut to the specified torque.

inspection after lnstallation

Steering effort

(1) Pull the hand brake lever.

(2) Run the engine to warm the hydraulic oil to an

operation temperature of 40 to 60

(104 to 140

(3) Attach a spring scale to the rim (or a spoke) of the

steering wheel, and measure the steering effort required

to turn the steering wheel clockwise or

counterclockwise from the straight-ahead position.

Steering effort

13 N (1.3 kgf)

(tangential force)

STEERING SYSTEM

2. Steering valve

Removal

Remove the cover 4 around the steering column.

Face the elbow right

downward to install.

(2) Disconnect four hoses connected to the steering valve.

Tightening torque of

(3) Remove the bolt 5 and then,

the steering valve

34 to 39

to 28.8

Installation

Follow the sequence of disassembly in reverse, paying

attention to the following points.

(1) Apply grease to the serration area on the lower part of

the steering shaft.

(2) Tighten the mounting bolt to the specified torque.

(3) Be careful about the orientation when installing the

elbow on the steering valve. Tighten it to the specified

torque.

3. Tilt lock lever

Top face of

Disassembly

1. Put match marks on the tilt lock lever and the nut for

convenience of reassembly.

2. Remove the bolt A and then, remove the tilt lock cover.

Reassembly

When match marks put at the time of disassembly

disappear or when the lever is replaced with a new one,

install the lever in the following sequence. (The illustration

Lever mounting

on the right shows the layout of related parts when the tilt

position is neutral and the column lock lever is locked.)

Tighten the nut to the tightening torque of

to 15

to 1.5

to 11.1

(This

represents a lever-locked condition.)

2. Select the optimal position for the tilt lock lever in a

locked condition and fit the tilt lock lever into the

serration of the nut

The optimal position is in an area where the

notch

on the bracket and the top face of the lever cross each

other.

3. Tighten the bolt A.

4. Loosen the tilt lock lever and check that the bracket

slides in the entire tilting area without interfering with

other parts.

STEERING SYSTEM

Suggestions for Disassembly

(1) Retaining ring removal

Remove the ring from the housing by prying its end out of

the groove. Do not damage the machined surface.

(2) Seal gland bushing removal

Position the control spool and control sleeve assembly so

that the pin is even with the center of the assembly.

Remove the gland bushing.

(3) Control spool and sleeve removal

Remove the control spool and sleeve assembly from the

housing by pulling it toward the end of the housing

opposite to the flange. Remove the pin from the

assembly.

prevent dama

g, slowly pull out

(4) Control spool and sleeve disassembly

Before removing the spool from the sleeve, put a

mark across the spool and sleeve so that the

spool can be installed in the same position.

Pull the control spool from the sleeve enough to permit

removal of the centering springs. Remove the centering

springs. Remove the spool from the sleeve by pulling it

toward the rear end of the sleeve while turning slowly.

STEERING SYSTEM

after disassembly

Check sliding areas between the sleeve and the housing

and between the sleeve and the spool.

(a) Check for sliding movement in sub-assembly

condition.

(b) If any defective movement is found, check sliding

surfaces.

If any defect such as

wear, scratch, burr

or rust is found, replace the entire unit with a new

one.

Reassembly

Sequence

1 Long housing

7 Seal gland bushing, Oil seal, Dust seal, O-ring

2 Control sleeve

8 Retaining ring

3 Control spool

9 Drive shaft, Spacer plate, O-ring

4 Centering springs

10 "Gerotor" set, O-ring

5 Pin

11 End cap, O-ring, Spacer, Bolts

6 Thrust needle, Race bearings

SYSTEM

Perform the

(1) For damaged parts, prepare new parts for

(2) Clean all

parts, blow off foreign

substances with compressed air and dry them.

(3) Prepare new

for an O-ring seal and lip

Reassemble each part while applying a light

coating of oil to them.

(2) Apply grease to O-rings.

(3) Do not wear

gloves when reassembling.

Lint may enter the valve.

Suggestions for Reassembly

(1) Reassembly of control spool and sleeve

Check the direction in which the spring groove of the

sleeve is aligned with that of the spool and then, slide the

spool into the sleeve while twisting the spool.

If there are any match marks put at the time of disassembly

or marks put by a manufacturer, check such marks.

200670

the control sleeve.

(2) Installation of centering springs

Align the spring grooves of the spool-and-sleeve and stand

the spool-and-sleeve on a flat bench. Use the spring

inserting tool to install springs. Place each set of three

springs back to back and pinch six springs in the tool with

notches on both sides facing downward. See the

illustration on the right.

As shown in the illustration, push one end of the springs

with fingers and push the springs into the spool-and-sleeve

groove. In case there is no inserting tool, assemble the

springs by inserting them

by one and right and left

alternately.

Spring inserting tool

97157 - 00100

SYSTEM

(3) Insertion of the control spool-and-sleeve assembly into

the housing

Insert the pin into the hole of the control spool-and-sleeve

assembly and align both ends of the pin with the outside

diameter of the sleeve. Insert the spool-and-sleevc

assembly into the housing from the rear (in the direction as

shown in the illustration).

Insert the spool-and-sleeve assembly while slowly twisting

it with the pin kept at a horizontal position. Insert the

spool-and-sleeve assembly until its rear edge face becomes

flush with the edge face of the housing. Do not insert any

further.

(4) Installation of thrust bearing

(5) Installation of seal gland bushing and seals

(a) Install the dust seal on the seal gland bushing to

place the flat side facing the bushing. Then install

the oil seal in the bushing.

(b) After installing the O-ring, fit the seal gland

bushing into the spool while turning the seal gland

Dust seal

Retaining ring

bushing. Drive the bushing into the specified

position by a plastic hammer. Check that the

bushing contacts the top face of the thrust bearing

race evenly.

Securely fit the retaining ring into the housing

groove.

Oil seal

209715

(6) Reassembling the spacer plate

(a) Clamp the housing in a vise equipped with soft

jaws or wrap the housing in a soft rag before

clamping the housing in the vise. Clamp lightly

over the flats of the flange. Do not over tighten the

vise jaws.

NOTE)

Check that the spool and sleeve are flush with or

slightly below the surface of the housing.

(b) Install the O-ring in the housing. Place the spacer

plate on the housing and align the bolt holes with

the tapped holes in the housing.

STEERING SYSTEM

(7) Reassembling the drive shaft

Turn the control spool-and-sleeve assembly to make the

port surface of the housing parallel with the pin. Insert the

drive shaft to engage the pin in the yoke of

drive shaft.

To insure positioning in the following work process, draw a

line such as line B in the illustration right below on the end

face of

drive shaft spline with a felt-tip pen.

(8) Reassembling the gerotor set

Root of

Face the O-ring side of the rotor set toward the spacer plate

set star

side and fit the rotor set into the drive shaft by aligning the

Spacer plate,

root (line A) of the rotor set with line of the drive shaft.

Check that lines A, B,

and are in parallel with each

Drive shaft

other.

Align bolt holes of the "Gerotor" set with the drive shaft

and star kept engaged.

This procedure is important in determining the valve timing

of this unit.

(9) Reassembling the end cap

Install the drive spacer in the gerotor set. Install the O-ring

in the end cap. Install the end cap in the gerotor set and

align the holes.

Apply oil to bolt threads and tighten bolts evenly in the

sequence as shown in the illustration on the right. The

tightening torque is shown in the table below.

Install the steering shaft in the spool and check that the

spool turns smoothly.

28.4

Tightening torque of end cap

(2.9

mounting bolt

STEERING SYSTEM

Troubleshooting

- No steering flow

Foreign materials clogged in spool -

Disassemble and clean.

pit

(2) Fatigued or damaged spring in the

- Replace spring.

spool

Defect in flow

Malfunction of relief valve

priority valve

(1) Low relief pressure

- Adjust relief pressure.

(2) Damaged valve seating surface

Replace valve assembly.

(3) Fatigued or damaged spring

- Replace springs and

adjust relief pressure.

Oil leak from relief valve

Damaged O-rings on the valve

- Replace O-rings.

body circumference

Clogging in "Gerotor"

Disassemble and clean.

Malfunction by spool seizure

Replace.

Stiff steering

Defect in

due to foreign material

wheel operation

steering valve

Damaged bearing

Replace.

Excessive tightening of end cap bolt

- Reassemble.

Repair or replace.

Defect in

Bent piston rod

- Replace.

Faulty installation of steering valve to

Readjust.

tilt column

Other defects

Flattened pipe

Replace.

Defect in

Seizure of spool or sleeve

Replace.

steering valve

Breakage of centering spring

- Replace.

Unstable steering

Trapped air

- Bleed.

Other defects

Flattened pipe

- Replace.

Faulty piston seal of steering cylinder

- Replace.

STEERING SYSTEM

A: Standard value

Truck Models

1 ton class

2 ton class

3 ton class

Items

Steering effort (at steering wheel rim)

or less

52.6 to 63.5

Tightening torque of steering wheel nuts

(5.4 to 6.5)

to 46.81

27 to 35

Tightening torque of steering bracket bolts

to 25.81

to 25

Displacement

Rotating torque in normal operation

Steering valve

ft]

Tightening torque of cap bolt

28 4 (29 )

28.4 (2

Steering system relief valve set pressure

(90

)

(105

)

(kgf/cm²) [psi]

SYSTEM

Structure and Functions

Outline

Hydraulic Circuit Diagram

Hydraulic Tank

11 -

Hydraulic Pump (Gear Pump)

11 -

Control Valve

Down Safety Valve

11 -

Lift Cylinder

Tilt Cylinder

Disassembly and Reassembly

Hydraulic Pump

11 - 14

Removal and Installation

Disassembly and Reassembly

11 - 15

Lift Cylinder

11 - 17

Removal and Installation

11 - 17

Disassembly and Reassembly

11 - 23

Tilt Cylinder

11 - 26

Removal and Installation

Disassembly and Reassembly

11 - 27

Flow Regulator Valve

11 - 29

Disassembly and Reassembly

.......................... 11 - 29

Piping

11 - 30

Suction Strainer and Return Filter

11 - 31

Removal and

11 - 31

Inspection and Adjustment

- 32

1. Hydraulic Tank

11 - 32

2. Control Valve

11 - 33

3. Descent Test

4. Forward Tilt Test

Troubleshooting

Control Valve

11 -- 43

HYDRAULIC SYSTEM

Structure and Functions

Outline

The illustrations show the load handling (pump motor) hydrauric system

on a 2 ton class truck with S4S diesel engine.

Main

1 Pump suction strainer:

10 Return line from steering valve

150 mesh metal strainer.

11 Oil feed line to steering valve

2 Hydraulic pump (gear pump):

12 Steering cylinder

A regular gear pump is directly coupled to the

13 Return line

engine PTO. See the "Hydraulic Pump" section

for details.

14 Line leading to top of lift cylinder piston:

This line is only installed in truck that have a lift

3 Hydraulic pump delivery hose:

cylinder with a return line.

is not installed in

The shape of this hose for the diesel-engine

trucks with 3.3 m (10.8 ft) or smaller lift. If this

models is different from that of the

line is not installed, the branching hole from

engine models, as the hydraulic pump locations of

return line 13 is closed with a blind plug.

these two models are different.

15 Return filter

4 Hydraulic control valve:

This cartridge-type filter should be replaced at

This valve has a built-in flow regulator valve.

every oil change.

5 Oil feed line to lift cylinder:

16 Level gauge

6 Tilt cylinder

17 Oil filter cap

7 Piping to tilt cylinder

8 Steering valve

9 Oil feed line to steering valve P port:

This line constitutes a part of the

flow

passage.

HYDRAULIC SYSTEM

Hydraulic Tank

Main components

Hydraulic tank

Element

Level gauge

Tank cover

Parts welded to tank cover

(a) Suction pipe

(b) Pipe for return line

Suction strainer

Return filter

Hydraulic pump

Pump suction line

Pump delivery line

The hydraulic tank is located in the center of the right

Return filter 7 is attached to the end of return pipe (b).

side of the frame and composes a part of the frame

The return filter is a cartridge type of 15

with an

structure.

integral relief valve. When the filter is clogged, the

relief valve activates and discharges unfiltered oil to the

Three pipes of (a),(b) and (c) are welded to tank cover

tank. Periodic replacement is important. In case of a

5 and to the end of each pipe are installed suction

new truck or a large-scale overhaul involving parts

strainer 6, return filter 7, level gauge 4 and cap 2.

replacement, replacement of the oil filter after the first

Therefore, parts in the tank can be taken out as an

month is recommended.

assembly if the tank cover is removed. Replacement of

the filter and cleaning of the strainer can be easily

Suction strainer of the pump is 150 mesh screen

carried out if tank cover 5 is removed.

gauze. When replacing oil, clean the suction strainer.

Level gauge 4 is inserted in pipe for a level gauge (c)

In case of a wet-type single disc clutch truck, the return

and the opening of pipe (c) is blocked with cap 2 with

oil line is installed to the side of the tank.

an element.

The drain plug is installed at the

of the tank.

Air moving in and out of the tank caused by fluctuation

of oil level in the tank during operation occurs through

two air holes provided on the side of cap 2. Element 3

assembled in cap is a filter to prevent outside polluted

air from entering the tank.

SYSTEM

Hydraulic Pump (Gear Pump)

Pump installed on engine

(example: S4S diesel engine, ton class)

209755

1 Front cover

8 Gasket (shaped like 3)

2 Rear cover

9 Gasket

3 Body

10 Hexagon socket head bolt

4 Drive gear

11 Washer

5 Driven gear

12 Shaft seal

6 Side plate

13 Snap ring

7 Bushing

Type of pump

of pump

The pump in a standard truck is a single-gear pump as

The pump is directly installed to the engine front PTO,

shown in the above illustration.

but installed sides are reversed left to right for a

gasoline engine and a diesel engine.

A low-noise type pump is available as an option. This

low-noise type has reduced noises produced by

Gasoline engine: The pump is installed to the left side

discharge pressure pulsation by making backlash

viewed from the flywheel side.

between gears smaller, and thus leak amount between

Diesel engine: The pump is installed to the right side

gears smaller compared to a normal type. The

viewed from the flywheel side.

appearance and structure of the low-noise type are the

as those of the standard type except for the

Piping around pump

number of teeth.

As the installed location of the pump is different

between the gasoline engine and diesel engine, shapes

of the suction piping and delivery piping around the

pump are different.

HYDRAULIC SYSTEM

Control Valve

e of four-valve

210109

Lift control lever

port of pump pressure oil

Tilt control lever

PF: Supply port of pressure oil to steering system

Return port to tank

Attachment

control lever

T2: Return port from steering system

Attachment

control lever

Al: Port to lift cylinder

cover section (with built-in flow priority

A2: Port to tilt cylinder rod

valve)

B2: Port to tilt cylinder head

Combination section (with built-in lift valve, tilt

valve and flow divider valve)

Attachment section

End section (with built-in unloader valve

Unloader valve (with solenoid)

Most parts of this hydraulic valve move mechanically.

When the operator moves the control levers (1 through

4), the spool valve moves up and down and supplies and

returns pressure oil to corresponding hydraulic cylinders.

For detailed structure and operation, and disassembly and

reassembly, refer to the "Control Valve" section (pages

11-43

11-58).

HYDRAULIC SYSTEM

Lift Cylinder

1. Second lift cylinder for simplex mast and triplex mast

There are two types for the above lift cylinder: one with a return pipe and the other without a return pipe. The

lift cylinder without a return pipe is provided with a check valve in the piston instead of a return pipe. This is

called an internal drain type cylinder.

Regardless of presence or absence of a return pipe, the bottom of the piston is provided with a cushion

mechanism for soft landing.

(1) Cylinder without a return pipe

Mast used:

Simplex mast with raised height of 3.4 m (11.2 ft) or less

(2) All triplex

Detail of inside

Groove

Inflow and

outflow of oil

stroke:

23 mm (0.91 in.)

Main components

1 Cylinder tube

5 Cushion bearing

8 Bushing

2 Piston rod assembly

Check valve

9 Wiper ring

3 Cylinder head

7 U-ring, Backup ring

X-ring

4 Pipe (integrated with cylinder

tube)

2. Cylinder with a return pipe

Mast used: Duplex mast with raised height of 3.5 m (11.5 ft) or higher

Detail of inside

Inflow and

outflow of oil

cushion stroke:

23 mm (0.91 in.)

Main

1 Cylinder tube

5 Cushion bearing

8 Wiper ring

2 Piston rod assembly

6 U-ring, Backup ring

9 U-ring

3 Cylinder head

7 Bushing

4 Pipe (integrated with cylinder

tube)

HYDRAULIC SYSTEM

Cylinder dimensions (The cylinder length and stroke vary depending on raised height )

Unit: mm (in.)

Model

1 ton class

2 ton class

3 ton class

3.5 m (11.5 ft) or higher

45 (1.77)

55 (2.16)

63 (2.48)

23 (0.91)

Yes

Triplex

45 (1.77)

55 (2.16)

63 (2.48)

23 (0.91)

Cushion mechanism when piston descends

Action during piston descent

Entrapped oil (A)

Groove

Outflow

The above illustration shows a condition in which piston

Outside diameter

rod assembly 2 descends with its self weight and pipe 4

The inside diameter

and cushion bearing 5 are beginning to fit in. Cushion

bearing 5 is pushed upward by entrapped oil (A) and

piston and cushion bearing 5 make surface contact at

area. This blocks the passage (a). The only outflow

passage for entrapped oil (A) is clearance (b) between the

bore of cushion bearing 5 and the outside of pipe 4. This

Clearance of approx.

passage (a) becomes narrower as the piston descends

0.1 mm (0.004 in.)

further. Therefore, the descending speed of the piston

Cushion bearing

209761

becomes gradually slower and impulsive contact is

avoided.

Image of pipe and cushion bearing

HYDRAULIC SYSTEM

Action during piston ascent (initial stage)

Passage (a)

Groove

Inflow

Passage (b)

209762

The above illustration shows a

immediately

This action opens

(B) area, causing the passage (a)

after the piston rod assembly ascends. Oil that flows in

to open. Oil from the passage (a)and passage (b) which

acts on the center of the piston, ascending piston rod

opens from the beginning flows in the piston bottom,

assembly 2 slightly. At the same time, cushion bearing

acting on the entire bottom surface of the piston and

5 descends by being pushed by oil that flows in.

pushing piston rod assembly 2 upward.

Cylinder of internal drain type

Entrapped oil and air

(There normally tends to be

negative pressure in this area.)

Groove

^\Check valve

209763

The above illustration shows a condition in which the

and discharges oil and air to pressure oil (internal

piston rod assembly ascends to the vicinity of the

drain).

highest position. When pressure of oil and air

entrapped between the rod and cylinder exceeds the

set pressure of the check valve, the check valve opens

2. Second lift cylinder for duplex mast

Inflow and outflow

Main components

1 Cylinder tube

4 Holder

7 Check valve

2 Rod

5 Cylinder head

8 Spring

3 Piston

6 Cushion spool

Bleed valve

HYDRAULIC SYSTEM

Action

Pressure oil first flows through the hollow area inside

piston rod 2 and enters the first lift cylinder. As the inside

diameter of the first lift cylinder is larger than that of the

second lift cylinder, the first lift cylinder ascends first. The

second lift cylinder starts to ascend after the first lift

cylinder has completed ascent.

This cylinder is provided with a cushion mechanism which

prevents the piston bottom from impulsively contacting the

cylinder bottom during piston descent. (Refer to the

illustration below.)

Bleed valve 9 is a valve for bleeding air when the hydraulic

system is overhauled.

Action during piston descent

7 Check valve

6 Cushion spool

The illustration on the right explains movement of cushion

Fig.

8 Spring

when the piston descends. (To the right of the

illustration is the piston bottom.)

Fig. This illustration shows a condition in which

cushion spool 6 does not contact the cylinder

bottom. Cushion spool 6 extends out by spring 8.

Fig. 2: This illustration shows a condition in which

cushion spool 6 contacts the cylinder bottom and

6 Cushion spool

gets under check valve 7 slightly. The check valve

Fig. 2

Entrapped oil (A)

area

moves to the left, blocking the

area. Oil (A)

below the underside of the piston is discharged

through holes (two rows on the right) of cushion

Outflow

spool 6.

For the shape of the check valve, refer to the image

drawing on the following page.

Fig. 3: As the piston descends, cushion spool 6 gets under

check valve further. As a result, the number of

Fig. 3

holes through which oil can pass decreases and

discharge of entrapped oil (A) is restricted. The

descending speed of the piston becomes slower and

Outflow

impulsive contact is avoided.

SYSTEM

Action during piston ascent

Fig. 4

7 Check valve

The illustration on the right explains movement of the

check valve when the piston ascends.

Fig. 4: The illustration shows a condition immediately

Inflow

before piston ascent. Oil which flows through the

hollow area in cushion spool acts on check valve

Fig. 5: Pressure oil pushes check valve 7 to the right.

Pressure oil flows along the plane of the check

Initial stage of ascent

3 Piston

(Oil flows alona this

valve and flows to the underside of the piston. The

"triangular shape" of check valve 7 is designed to

Shape of

increase the initial inflow volume.

check valve

The piston starts to ascend.

plane seats.)

Fig. 6: The illustration shows a condition in which cushion

Fig. 5

7 Check valve

spool 6 has left the cylinder bottom and is

ascending.

Inflow

7 Check valve

6 Cushion spool

Fig. 6

Inflow

HYDRAULIC SYSTEM

3. First cylinder for duplex mast and triplex mast

Detail of inside

Space (B) Cushion oil is filled in this area.

and

outflow

Air chamber (A)

Oil passage

Piston

209767

components

1 Cylinder tube assembly

6 Wiper-ring

2 Piston rod assembly

Seal ring assembly

3 Cylinder head

8 Slide ring

4 Bushing

9 Check valve

5 U-ring

10 Stand tube

Action

This cylinder, mounted on the center of the mast, acts

In the descending stroke of the piston rod, cushion oil

first during ascending stroke of the fork.

in air chamber A is sucked in space B. The air

chamber, stand tube, and check valve are related parts

pressure oil acting on the piston bottom. For

prevention of an impulsive approach of the piston and

Extra leaked oil which leaks from around the piston and

the cylinder head at the last stage of its ascent, cushion

enters space

returns from stand tube 1 0 to the

oil is always filled in space between the cylinder tube

cylinder bottom via check valve 9 at the last stage of

and the piston rod. When the piston rod ascends, it

cylinder ascending.

ascends while pushing out cushion oil to air chamber A

impulsive.

filled in the overhauled cylinder.

Cylinder dimensions (The cylinder length and stroke vary depending on raised height )

Unit:

(in.)

Rod diameter

inside

Cylinder outside

Truck model

Mast type

diameter (ID)

diameter (OD)

1 ton class

55 (2.16)

70 (2.76)

82 (3

Cylinders for the duplex mast and the triplex mast

2 ton class

55 (2.16)

75 (2.95)

86 (3.39)

are of the same

and same type.

3 ton class

65 (2.56)

90 (3.54)

105 (4.13)

HYDRAULIC SYSTEM

Tilt Cylinder

Main components

Cylinder

5 Socket

9 Piston seal

13 Buffer ring

2 Rod

6 Bearing

10 O-ring

14 Nut

3 Bushing guide

7 Seal

11 Dust seal

15 Clamp bolt

4 Piston

8 Bushing

12 Packing

The tilt cylinder is a double-acting type. To adjust right

and left imbalance of tilt angles when the mast is attached,

loosen the clamp bolt and turn the piston rod with a spanner

applied to its A area.

Seal 7 extends grease interval from the grease nipple.

Installation of this seal has extended grease interval to 500

service hours.

Cylinder dimensions (Cylinder length and stroke vary

depending on tilt angles of forward and backward tilt. )

Unit: mm (in.)

Truck

Rod diameter

Cylinder inside

Cylinder outside

model

diameter (ID)

diameter (OD)

HYDRAULIC SYSTEM

Disassembly and Reassembly

Hydraulic Pump

Removal and Installation

S4S diesel engine

209769

Sequence

1 Pump delivery hose

3 Pump mounting bolt

2 Pump suction hose

4 Pump

Suggestion for Removal

Installation

Precautions for removal:

To install, follow the reverse of removal sequence, and

do the following steps:

(1) The installed positions and sizes of the suction hose

and delivery hose differ by model.

(1) Apply grease to the spline of the pump shaft before

installation.

(2) Cover the pump and its surroundings with shop

cloths in preparation for spilled oil.

(2) Insert the gasket (diesel engine) or O-ring (gasoline

engine) between the pump and engine PTO.

(3) Take care not to allow foreign particles to enter the

pump and hose from detached parts.

(3) Perform test operation after installing the pump.

Refer to page 11-16.

HYDRAULIC SYSTEM

Disassembly and Reassembly

Disassembly

Parts marked with are components of the seal kit.

Parts not

with are non-deliverable parts.

Sequence

1 Rear cover, Bolt, Washer, Bushing

5 Drive gear

2 Front cover, Snap ring, Shaft seal, Bushing

6 Driven gear

3 Gasket, Gasket (shaped

7 Side plate

4 Side plate

8 Body

Note: (1) The hydraulic pump is to be overhauled by

Suggestions for Disassembly

the manufacturer. Where it has to be

(1) As front cover 2 and rear cover

made of

overhauled in field, be sure to follow the

aluminum alloy, get easily scratched, do not

suggestions for disassembly. Remember,

forcibly tap

with a hammer. Use a wooden

field overhauling will release the

hammer or plastic hammer.

manufacturer from any warranty claims.

(2) When disassembling, do not remove the body, gear

(2) Do not remove oil seal 2 and bushings

and bushing by forcibly tapping them with a

unless they are defective to require

hammer.

replacement.

(3) Place disassembled parts in orderly sequence.

Especially, do not mistake the relative position of

the gear and bushing side plate.

HYDRAULIC SYSTEM

and Repair

Drive and driven gears

Check the gear teeth for wear, chipping or other

defects.

(2) Check the side faces of the gears for wear or damage.

(3) Check the shafts for wear or damage.

2. Covers, body and bushings

Check these parts for wear or damage.

200344

To reassemble, follow the reverse of disassembly sequence,

and do the following steps:

Replace the seal kit parts with new ones.

(2) Completely remove oil or grease on the mating

surfaces of covers

and body 8.

(3) Visually check all the parts for cleanliness and apply

hydraulic oil to the inside surface of the body before

reassembly.

(4) Apply grease to the lip of the shaft seal.

(5) Be careful not to give damage to the lip of shaft seal by

spline edges of drive gear 5.

(6) Tighten the bolts evenly and progressively.

(7) The pump is assembled properly if the pipe wrench

fitted on the pump shaft can be turned easily by hand.

Test operation

Perform test operation after installing the pump.

Check that the oil amount in the hydraulic tank is

sufficient.

(2) Attach a pressure gauge to the pump delivery hose.

Refer to page 11-33 "Main Relief Valve."

(3) Start the engine, raise the adjusting screw of the main

relief valve in sequence from to 18.1

to 180

kgf/cm²) [0 to 2625 psi], and check the temperature rise

of the

body by touching it by hand. If the

temperature rise of the pump body is substantial

compared to the oil temperature rise, disassemble again

for checking.

(4) Set the relief valve to the specified pressure.

(5) Measure the lifting speed of the fork under no load. If

the speed is to the specified value, the pump discharge

volume is normal.

(6) Check that the fork operates normally by raising and

lowering it under load.

HYDRAULIC SYSTEM

Lift Cylinder

Removal and Installation

Simplex mast

Sequence

1 Hose guard

4 Set bolt, Shim

2 Return hose (if equipped)

5 Cylinder clamp (Cushion, Collar, Shim)

3 High-pressure hose

6 Lift cylinder, Bracket

Suggestions for Removal

From right-hand

Removal of hose guard

lift cylinder

Remove the hose guard from the front while the lift bracket

is placed at the bottom.

2. Removal of return hose (if equipped)

Start the engine, raise the lift bracket to the highest

To tank

position, and stop the engine. Then, remove return hoses

on the right and left cylinders from the connector.

Note: Place a drip pan below the connector to catch the oil.

From left-hand

lift cylinder

HYDRAULIC SYSTEM

3. Lowering of lift bracket

Gently operate the lift lever to lower the lift bracket.

4. Disconnecting high-pressure hoses

Disconnect the high-pressure hoses at the joints indicated

Right-hand cylinder

Left-hand cylinder

by arrows. Use a drip pan to catch oil flowing out of the

hoses.

Removing set bolts

Remove the set bolt at the top of each lift cylinder. Lift

the inner mast to separate the cylinder rod ends. To lift

the inner mast, hitch a sling around the

with

protective rag.

:e: The rod end of either lift cylinder is shim adjusted

to eliminate the difference in stroke between the

cylinders. Before removing the set bolts, make a

record of the amount of shims fitted to each cylinder.

Tie wood blocks under the inner mast and detach the

sling. Use the blocks strong enough to support the

mast.

HYDRAULIC SYSTEM

6. Removing lift cylinders

Attach a lifting sling before removing the cylinder clamp.

Lift the cylinder from the rear side of the mast, and remove

the cylinder.

Installation

To install, follow the reverse of removal sequence, and do

the following steps:

(1) Extend and retract the lift cylinders several times under

condition to bleed air out of the cylinder

circuits and to make sure that the cylinders moves

smoothly.

(2) Check the oil level in the hydraulic tank with an oil

level gauge. (Refer to the topics

Tank" in

the following section "Inspection and Adjustment.")

(3) Check the lift height.

(4) After the lift cylinders or piston rods have been

replaced, check for difference in stroke between the

two cylinders. (Refer to "GROUP 12 MAST AND

FORKS

HYDRAULIC SYSTEM

(2) Position the mast upright. Raise the inner mast until

upper rollers 8 of the lift bracket become free. Then,

slowly move the truck in reverse to separate from lift

bracket 2.

2. Removing first lift cylinder

(1) Hitch a sling on the first lift cylinder 3, and suspend it

with a crane. Wind the rope securely to prevent

slipping.

(2) Remove lift cylinder connecting bolts and mounting

bolts, and gently remove the first lift cylinder 3.

Removing second

cylinders 5

Disconnect hoses from the second lift cylinders 5.

Remove stopper bolts at the upper sections of the

second lift cylinders 5, and lift the inner

for

duplex mast or middle mast for triplex mast

approximately 55 cm (21.67 in.) using slings.

HYDRAULIC SYSTEM

(3) Place wood blocks under the inner mast (for duplex

mast) or

mast (for triplex mast).

Make sure the right and left wood blocks are the same

in height.

Hitch a sling to second lift cylinder 5 behind the mast,

remove cylinder clamp retaining bolts, and gently

remove second lift cylinder 5.

Wind the sling securely to the cylinder. The cylinder

cannot be lifted straight up since the mast

is located above the cylinder, Tilt the cylinder

and move it away from the cross-member to remove.

Be careful not have the hands caught between the

cylinder and mast.

Installation

To reinstall, follow the removal sequence in reverse, and do

the following steps:

Install chain wheel support assembly 4 parallel to a

line connecting the centers of chain anchor bolt holes

on first lift cylinder 3 to prevent chains from twisting.

(2) Adjust the chain tensions.

(Refer to "Chain Tension Inspection" on page 12-33.)

(3) Extend and retract the lift cylinders several times under

Good

Bad

no load condition to bleed air out of the cylinder

207638

circuits and to make sure that the cylinders move

smoothly.

(4) After proper operation is confirmed, check the oil

level.

HYDRAULIC SYSTEM

Disassembly and Reassembly

1. Second cylinder for simplex mast and triplex mast

Disassembly

Tightening torque

1 ton class: 196

45.1

(20 1: 4.6

(M49 x 1.5)

2 ton class: 235 153.9

(24 1: 5.5

(M54 x 1.5)

Apply liquid packing to

3 ton class: 275 161.8

(28

6.3

(M59 x 1.5)

circumference when

pressing in.

Apply grease when assemblina

Seal in grease.

(Adhesion to

bushing is acceptable.)

Apply THREEBOND

when screwing in.

Sequence

First, disassemble into the three parts of the following I to Ill, and then disassemble the three parts.

Head sub-assembly

10 Snap ring

Consisting of the following parts, 1 thru 5.

11 Cushion bearing

1 Cylinder head

12 Check valve

2 Wiper ring

13 O-ring

3 X-ring

Cylinder tube sub-assembly

4 O-ring

Consisting of the following parts, 1 4 and 1 5.

5 Bushing

14 Cylinder tube assembly

Piston rod sub-assembly

15 Plug

Consisting of the following parts, 6 thru 13

6 Piston rod assembly

Note: The illustration shows a cylinder of the internal

7 Backup ring

drain type without a return pipe. For structure

8 U-ring

of the cylinder with a return pipe, refer to page

9 Bushing

11-7.

Suggestions for Disassembly

3. Rings and packings

Pulling out piston

(1) Check lips for damage, wear, or deterioration.

Be careful not to damage the piston seals and cylinder

Reassembly

Inspection after disassembly

sequence, and do the following steps:

1. Cylinder tube

(1) Clean the disassembled parts with high flash-point

solvent. Blow them dry with compressed air;

Check the bore wall for wear, grooving, scratching

however, this does not apply to rubber parts.

or rusting.

(2) Apply hydraulic oil to the bore surface of cylinder

(2) Check the welds for cracks or other defects.

and also to the piston seal, O-ring, backup ring,

2. Piston rod

buffer ring, packing and dust seal.

(1) Check the rod for deflection.

(3) Apply liquid gasket (THREEBOND

to the

(2) Check for surface flaws such as grooving,

thread.

scratching, rusting or wear.

Tighten to the specified torque using hook wrench.

SYSTEM

2. Second lift cylinder for duplex mast

Disassembly

Unit:

Tightening torque

1 ton class: 206

39.2 (21

4.0)

(M52 x 2)

2 ton class: 206

39.2 (21

4.0)

(M52 x 2)

3 ton class: 235

53.9 (24

5.5)

(M57 x 2)

Be careful of the direction

when installing. Face slit

toward spring side.

THREEBOND

when screwing in.

Sequence

First, disassemble into the three parts of the following I to

and then disassemble the three parts.

I. Holder sub-assembly

Piston rod sub-assembly

Consisting of the following parts, 1 thru 5.

Consisting of the following parts, 8 thru 15.

1 Holder

8 Rod

2 Wiper ring

9 Piston

3 Backup ring

10 Slide ring

4 U-ring

11 Set screw

5 O-ring

12 Check valve

Head sub-assembly

13 Cushion spool

Consisting of the following parts, 6 and 7.

14 Spring

6 Head

15 Snap ring

7 Bushing

Cylinder tube sub-assembly

Consisting of the following parts, 16 and 17

16 Tube assembly

17 Plug

Suggestions for Disassembly

3. Rings, packings and threads

Pulling out piston

(1) Check lips for damage, wear or deterioration.

Be careful not to damage the piston seals and cylinder

(2) Check threads for damage.

bore wall when pulling out the piston from the cylinder.

after disassembly

To reassemble, follow the reverse of disassembly

1. Cylinder tube

sequence, and do the following steps:

(1) Check the bore wall for wear, grooving, scratching

(1) Clean the disassembled parts with high flash-point

or rusting.

solvent. Blow them dry with compressed air;

however, this does not apply to rubber parts.

Check the welds for cracks or other defects.

(2) Apply hydraulic oil to the bore surface of cylinder

2. Piston rod

and also to the piston seal, O-ring, backup ring,

(1) Check the rod for deflection.

buffer ring, packing and dust seal.

(3) Tighten threads of important parts to the specified

scratching, rusting or wear.

torque as per the above illustration.

SYSTEM

3. First lift cylinder for duplex mast and triplex mast

Disassembly

Tightening torque

I ton class: 382

(39

(M75 x 2)

2 ton class: 422

(43

(M80 x 2)

3 ton class: 530

122

(54

(M95 x 2)

(0.4

r ^{Tightening torque: 3.92}

Sequence

First, disassemble into the three parts of the following I to

and then disassemble the three parts.

I. Cylinder head sub-assembly

Piston rod sub-assembly

Consisting of the following parts, 1 thru 6.

Consisting of the following parts, 7 thru 1 2.

1 Cylinder head

7 Rod

2 Wiper ring

8 Piston

3 U-ring

9 Slide ring

4 Bushing

10 Seal ring assembly

5 O-ring

11 Check valve

6 O-ring

12 Snap ring

Cylinder tube sub-assembly

Consisting of the following parts, 1 3 and 14.

13 Cylinder tube su

bly

14 Plug

Suggestions for Disassembly

Suggestions for Reassembly

Be careful not to damage the cylinder bore wall when

To reassemble, follow the reverse of disassembly

pulling out the piston rod from the cylinder.

sequence, and do the following steps:

Inspection after disassembly

Clean the disassembled parts with high flash-point

solvent. Blow

dry with compressed air;

Cylinder tube

however, this does not apply to rubber parts.

(1) Check the bore wall for wear, grooving, scratching

(2) Apply hydraulic oil to the bore surface of cylinder

or rusting.

and also to the piston seal, O-ring, backup ring,

(2) Check the welds for cracks or other defects.

buffer ring, packing and dust seal.

2. Piston rod

(3) Be careful of the direction when installing the snap

(I) Check the rod for deflection.

ring 12 of the check valve.

(2) Check for surface flaws such as grooving,

(4) Fill hydraulic oil as cushion oil in the space

scratching, rusting or wear.

between the tube and rod before reassembling the

cylinder head.

3. Rings, packings and threads

(5) Tighten threads of cylinder head 1 to the specified

(I) Check lips for damage, wear or deterioration.

torque as per the above illustration.

(2) Check threads for damage.

HYDRAULIC SYSTEM

Tilt Cylinder

Removal and Installation

Removal

Sequence

Tilt cylinder pin

Hoses (2 pcs. per one

cylinder)

3 Tilt cylinder pin

Tilt cylinder

Start by:

3. Removing tilt cylinder

(a) Lower the forks to the bottom, and tilt the mast

Remove tilt cylinder pin 3, and remove the cylinder.

fully forward.

left, in the top cross-member of outer mast, and

support the weight of the mast

a hoist.

After installing tilt cylinders, check the balance of

tilting angle. Adjust if necessary. Refer to

Suggestions for Removal

"Tilt Angle Adjustment (all mast models)" on page

12-38.

Retracting piston rod

Remove tilt cylinder pin I , start the engine and retract

the piston rod fully, then stop the engine.

2. Disconnecting hoses

Disconnect hoses 2 from the cylinder at the connectors.

Use a drip pan to catch oil flowing out of the cylinder.

Attach caps to the connectors of the cylinder to protect

the threads of the connectors and to prevent oil from

flowing out of the cylinder when the cylinder is

removed.

HYDRAULIC SYSTEM

Disassembly and Reassembly

Disassembly

Tightening torque

1 ton class: 265

(27

3.0

2 ton class: 314

(32

3.2

3 ton class: 373

(38

3.7

After tightening nuts,

crimp two locations.

Tightening torque

1 ton class: 127

9.8

(13

[94

7.2

Tightening torque:

2 ton class: 235

19.6

(24

2.0

14.5

153 to 182

3 ton class: 392

(40

2.5

18.4

(16 to 19

13 to 134

209772

Sequence

First, disassemble into the three parts of the following I to

and then disassemble the three parts.

I. Tilt socket sub-assembly

Piston rod sub-assembly

Consisting of the following parts, 1 thru 5.

Consisting of the following parts, 11 thru 15.

1 Bolt, Nut

Nut

2 Tilt socket

12 Piston

3 Seal

13 Piston seal

4 Bearing

14 Spacer

5 Grease nipple

15 Rod

Guide bushing sub-assembly

IV. Cylinder sub-assembly

Consisting of the following parts, 6 thru 1 0,

Consisting of the following parts, 16 and 17.

6 Guide bushing

16 Cylinder assembly

7 Dust seal

17 Bushing

8 Packing

9 Buffer ring

10 O-ring

Note: (a) Before disassembly, make a record of the

dimension from the holder edge to the socket

edge when the rod is fully pushed in. The

record will be helpful for reassembly.

(b) Do not disassemble the tilt socket bearing

and cylinder tube bushing unless

abnormality, is found on inspection.

unless abnormality, is found on inspection.

HYDRAULIC SYSTEM

Suggestions for Disassembly

Removing bushing

(I) Wrap the cylinder with a rag, and clamp it in a vise.

Using a wrench, remove the bushing from the cylinder.

(2) When removing the bushing from the piston rod, be

careful not to rub damage the buffer ring, packing,

ring against the threads of the piston rod.

Inspection after disassembly

1. Cylinder tube

(I) Check the bore wall for wear, grooving, scratch marks

and rusting.

(2) Check the welds for cracks.

2. Piston rod

Check for surface flaws such as grooving, scratch marks,

rusting and wear. The rod

be replaced if its threads

show a sign of stripping or any other damage.

3. Rings and packing

(1) Check each ring and packing for damage or distortion.

(2) Also check for deterioration due to aging.

Precautions for reassembly of lift and tilt cylinders

(I) Carefully clean all parts to remove any foreign particle.

(2) Reassemble the cylinder in the reverse sequence of the

disassembling, apply hydraulic oil to the bore wall of

the cylinder tube, and also to sealing parts - O-rings,

piston seals, dust seals and packings. Pay attention to

the correct part arrangement.

(3) When clamping the cylinder tube in the vise , be

careful not to distort the tube.

(4) Install the piston seal as follow:

(a) Before fitting the piston seal, squeeze it by hand

five or six times to soften it.

(b) Hold the piston in a vise, taking care not to damage

any part of the piston. Apply a thin coat of

hydraulic oil to the seal. Fit a portion of the seal to

the groove, and push the other portion into the

groove as shown.

(5) Tighten the thread to the specified torque.

to the

previous page for the torque.

HYDRAULIC SYSTEM

(Installed on trucks with FC control valve only)

Disassembly and Reassembly

Disassembly

Lock nut

4 Piston, Pin, Washer, Spring, Valve

2 Plug, O-ring

5 Valve body

3 Spring, Shims

Note: Before disassembling, measure the protrusion of the

plug. On assembling, adjust the protrusion as

before.

Check the spring for fatigue.

(2) Check the sliding and contact surfaces of valve and

piston for damage.

(3) Check the sliding surfaces of piston and valve body for

damage.

Note: Replace the flow regulator valve as an assembly if

any part is defective.

Reassembly

To reassemble, follow the reverse of disassembly sequence.

HYDRAULIC SYSTEM

Suction Strainer and Return Filter

Removal and Installation

Removal

Installation

Remove the suction hose from the pump.

To install, follow the reverse of removal sequence, and

(2) Remove the hose of the return line from the control

valve.

(1) Tighten the strainer and filter to the specified

torque.

(3) Remove all of tank cover mounting bolts.

(4)

care to avoid sucking in air.

tank as shown in the above illustration.

(5) Remove the suction strainer and return filter.

Inspection

(1) Clean the suction strainer.

(2) The return filter is a periodic replacement part.

Replace it when changing oil. In case of a new

truck or carrying out an overhaul, replace it after

the first month.

HYDRAULIC SYSTEM

and Adjustment

Hydraulic tank

Daily check of oil

Check oil for level, dirt and white turbidity (entry of air,

mixing of water).

(2) Adequate oil level during daily check

Check the oil level with the mast lowered.

Simplex mast: Between N and L level

Triplex mast: Between and level

The oil lcvcl must not exceed the level with any mast

and attachment when they are lowered.

Maximum level for

triplex mast

(3) Method of filling hydraulic tank with oil

Maximum level for

Use hydraulic oil

simplex mast

Minimum

(a) Fill the hydraulic tank with oil with the mast

lowered.

(b) Repeat ascent and descent of the mast a few times,

and then lower the mast.

maximum acceptable level is the level for the

simplex mast and the H level for the triplex mast.

If the level is low, replenish oil.

The oil level in the tank must not exceed the H

level with any combination of the mast and

attachment when the mast is lowered.

(4) Inspection of suction strainer

Check the suction strainer for damage and clogging. Clean

it if it is dirty.

(5) Inspection of return filter

Check the return filter for damage. As this part needs

periodic replacement, replace it when the replacement

interval is reached.

Refer to page 11-31 "Removal and Installation of Suction

Strainer and Return Filter."

HYDRAULIC SYSTEM

2. Control Valve

(1) External leakage

(a) Check for oil leaks from the joint between adjacent

valve housings sealed by O-ring.

(b) Check for oil leaks from the screw connections.

(2) Internal leakage

It is not practical to check the control valve alone for

internal leakage. How to check the control valve in place

(under normal operating conditions) will be described.

The internal leakage to be checked includes leakages

occurring at the lift spool, tilt spool, tilt lock valve and

check valves at the oil temperature of approximately 50°C

(a) Pick up a load equal to the rated capacity, and lift it

approximately 1 m (3 ft) high. Tilt the mast about

3" to forward, and stop the engine.

(b) Quickly disconnect the oil return hose, and start

collecting the oil coming out of this hose as shown.

Amount of oil collected for

20 cc (1.2 cu in.)

15 minutes

or less

tilts forward or the fork lowers) excessively in

spite of that the amount of oil collected for 15

minutes is less than 20 cc (1.2 cu in.), measure the

internal leakage of each cylinder.

(The

measurement is the assembly standard and not the

service limit.)

(3) Main Relief Valve

(a) Install a pressure gauge capable of measuring up to

25000

(250 kgf/cm²)

psi] to the delivery

hose connector. Use the gauge, connectors and

hose used for testing the gear pump.

(b) Start the engine and run it at the maximum speed.

Pressure gauge \

Move the tilt control lever to the backward tilt

position. If the pressure is relieved at 18142

(185

kgf/cm²)

psi] when the

tilt cylinders reach the end of their stroke, the main

relief valve setting is correct.

adjusting screw and, while observing the pressure

gauge reading, slowly rotate the adjusting screw

until the gauge indicates the prescribed set value.

(d) While holding the adjusting screw, tighten the lock

nut to secure the adjusting screw.

(e) After securing the adjusting screw, recheck the

setting.

Pump delivery hose

Remove the plug of

from the metal

Main relief valve setting

(185

kgf/cm²)

fittings of the pump delivery hose and install a

psi]

pressure gauge.

11-33

HYDRAULIC SYSTEM

(4) Adjustment of steering system relief valve

Steering system

g^aug^e

(a) Attach a pressure gauge capable of measuring up

relief

to 25000

(250 kgf/cm²) [35

psi] to the pump

delivery hose connector (illustration on the right).

(b) Set the control lever to neutral.

Turn the steering wheel to the extreme right or to

left to relieve oil in the steering system. The relief

pressure must be within the range in the table

below.

(d) If the relief pressure is outside the range, remove

delivery

the cap and turn the adjusting screw for

hose

adjustment.

(e) If the pressure is correct, tighten the lock nut and

check

relief pressure again.

Unit:

(kgf/cm²) [psi]

Truck Model

1 ton

2,3 ton

class

classes

Item

8800

10300

Set pressure of steering

(90

(105

)

system relief valve

3. Descent test

(1) Pick up a load equal to the rated capacity, place the

mast to a vertical position, lift the fork 1 to 1.5 m (3.3

to 4.9 ft), and stop the engine.

(2) Mark a reference line on the mast, and measure the

descent (retraction of the piston rods) for 15 minutes.

Divide the measured value by two to calculate the

retraction of piston rods.

Descent (retraction of piston rods)

50 mm (2 in.)

with rated load for 15 minutes

maximum

4. Forward tilt test

Pick up a load equal to the rated capacity, place the

mast to a vertical position, lift the fork about 50 cm (20

in.), and stop the engine.

(2) Measure the extension of tilt cylinder piston rod for 15

minutes.

Amount of forward tilt (extension

20 mm (0.8 in.)

of piston rods) with rated load for

maximum

15 minutes

HYDRAULIC SYSTEM

Troubleshooting

Not enough oil in hydraulic tank

Refill.

Oil viscosity improper

Change upon referring to "Fuel

and Lubricant Specifications" on

page 13-13.

Overload

Check working conditions and, if

over-loaded, urge the operator to

Hydraulic tank

stay within the load limit.

Local overheating of oil line due to

Clean oil line.

a large restriction to flow

Relief valve adjustment improper

Readjust pressure setting.

Pressure drop due to fatigued or

Disassemble or replace and

broken springs

readjust pressure.

Hydraulic

Gear

worn

Replace pump.

Outlet pipe or tube flattened, or

Repair or replace.

restriction to flow

Shortage of oil due to a natural loss

Replenish oil upon referring to

"Fuel and Lubricant Specifications"

on page 13-13.

Cylinders move

too slow

Oil leakage due to damaged oil line

Repair or replace.

and seals

Oil viscosity too high

Replenish oil upon referring to

"Fuel and Lubricant Specifications"

on page 13-13.

Gear pump does not pump oil

Check pump and piping; repair or

rewlace.

Cylinders move

Oil leakage from oil line

Check oil for level and condition;

too slow

add or change oil.

Gear pump internally leaking

Replace pump.

- Replenish oil upon referring to

"Fuel and Lubricant Specifications"

on page 13-13.

Cavitation

Check suction pipe for any flat

portion or loose connection;

retighten or replace.

(2) Check shaft oil seal for

airtightness; replace pump.

(3) Check pump body for any

Gear pump

outside interference; repair.

Pump case, drive

Pressure too high

Replace pump. (Check to see if

gear or pump port

relief valve setting is correct.)

Distortion or damage due to external -

Replace pump.

strain or stress

(1) Check to see if return line is

blocked or restricted.

(2) Check to see if pipe

connections have been

externally strained or stressed.

Oil leakage past oil seal

- Replace shaft seal.

- Oil leakage past sliding surfaces of

Replace whole pump assembly.

Oil leakage from

drive shaft

securing bolts loose

Retighten. Replace if needed.

Degraded performance of sealing

Replace gasket.

inside pump

HYDRAULIC SYSTEM

Relief valve set pressure lowered

Readjust pressure.

Relief valve piston seizure

- Wash piston and check to see if it

moves smoothly; or replace whole

Slow or no

relief valve assembly.

O-ring on relief valve body damaged-

Replace O-ring.

tilt cylinders

Control lever installed loose,

Readjust.

resulting in not enough spool stroke

Abnormal oil temperature rise

Check control valve spool for

misalignment; repair or replace.

Control

Load descends or

Control valve internally leaking

Replace a leaky block assembly.

mast tilts forward

Oil leakage from spool ring cap

Replace O-ring; check spool for

flaws and if any, repair or replace a

leaky block assembly.

Oil leakage

Loose plug

Retighten plug.

O-ring damaged

Replace O-ring.

Not enough oil in hydraulic tank

Replenish oil upon referring to

and Lubricant Specifications"

on page 13-13.

Mast will not lift

- Relief valve out of order, because of:

or tilt forward or

backward

Seized main valve

Replace.

(2) Broken valve spring

- Replace.

Gear pump defective

- Replace.

Relief valve out of order, because of:

(1) Too low a relief valve setting

Readjust pressure.

(2) Defective plunger or poppet seat - Replace.

Will not lift rated

(3) Fatigued spring

Replace.

(4) Damaged O-ring in valve case

Replace.

Gear pump defective

Replace.

Piston seals worn or damaged

Replace.

Lift and tilt

- Engine speed too low

Adjust engine.

cylinders

Control lever installed loose,

- Adjust.

Lifting speed is

resulting in not enough spool stroke

too slow

Tank strainer clogged

Clean or replace.

not delivering enough oil

Repair or replace.

Sleeve seized in flow regulator valve- Repair.

Dirt flow regulator valve,

- Clean, repair system and replace

abnormal resistance to flow due to

defective hose.

flattened hose or local clogging

HYDRAULIC SYSTEM

Piston rod distorted

Repair or replace.

- Air trapped in oil circuit

- Bleed air by operating cylinder

when actuated

through full stroke.

- Not enough oil in hydraulic tank

Refill.

Control valve spool internally

- Replace a leaky block assembly.

leaking

Sliding (inside) surface of cylinder

- Repair or replace.

tube slightly grooved

Load descends

fast

Sliding (inside) surface of cylinder

Replace cylinder assembly.

tube badly grooved

Piston seals broken or distorted

Replace seal kit.

Oil leakage from piping

Repair or replace.

- Control valve spool internally

- Replace a leaky block assembly

Lift and tilt

leaking

cylinders

Foreign particles lodged in packing

Replace packing.

(drift)

Piston seals damaged

Replace seals.

Other abnormal distortion, oil

Repair or replace.

leakage from piping

Lift cylinders

descend or tilt

Sliding surface of cylinder tube

- Repair or replace.

cylinders tilt

badly grooved or rusted at one point

forward (drift) at

Cylinder tube distorted

stroke

Replace.

Foreign particles lodged between

Replace.

sealing members such as oil seals and

dust seals

Oil leakage at

bushing

Oil seals and dust seals grooved

Replace.

O-rings damaged

Replace O-rings.

Cylinder abnormally distorted

- Repair or replace.

HYDRAULIC SYSTEM

Data

A: Standard value

Unit: mm (in.)

Forward tilt angle (standard truck with simplex mast)

degrees

Backward tilt angle (standard truck with simplex mast)

degrees

Lift cylinder descent amount (at rated load)

[Retracted length of rod, oil temperature at

50 (2) or less

45°C

mm (in

Tilt cylinder forward tilt amount (at rated load)

[Extended length of rod, oil temperature at

20 (0.8) or less

45°C (1

min.

Main relief valve setting

(185

(kgf/cm²) [psi]

8.8

10.3

Steering system relief valve setting

(105

)

(105

(kgf/cm²) [psi]

SHIMADZU CORPORATION

Hydraulic pump

Manufacturer's model

type single gear pump

Manufacturer of control valves

SHIMADZU CORPORATION

Tightening torque of return filter

49 1 9.8 (5.0 1 .O) [36 1 7.21

Tightening torque of suction strainer

ft]

HYDRAULIC SYSTEM

A: Standard value

Unit: mm (in.)

Truck Models

1 ton class

2 ton class

3 ton class

Items

Rod outside diameter 1

35 (1.38)

40 (1.57)

45 (1.77)

Cylinder inside diameter 2

Cylinder outside diameter 3

52 (2.05)

57 (2.24)

63 (2.48)

Thread size of cylinder head 4

M49

M54

M59

1961 45.1

235

53.9

275 161.8

Tightening torque of cylinder head 5

(2014.6)

(24

5.5)

(28

6.3)

Simplex mast with raised height of 3.4 m (11.2 ft) or less

All triplex masts

Second

cylinder for

simplex

mast and

triplex mast

Simplex mast with raised height of 3.5 m (11.5 ft) or higher

HYDRAULIC SYSTEM

Standard value

Unit: mm (in.)

Truck Models

ton class

2 ton class

3 ton class

Items

Rod inside diameter 1

16 (0.63)

20 (0.79)

Rod outside diameter

32 (1.26)

35 (1.38)

40 (1.57)

Cylinder inside diameter 3

45 (1.77)

50 (1.97)

Cylinder outside diameter 4

53 (2.09)

60 (2.36)

Thread size of holder 5

M52

M57

206

39.2

206

39.2

235

53.9

Tightening torque of holder 6

(2140)

Thread size of piston 7

M30

M33

M36

196

Tightening torque of piston 8

3.92

Tightening torque of plug

(0.4

0.09)

(0.4

0.09)

(0.4

0.09)

Second

0.661

cylinder for

3.92

Tightening torque of set screw

(0.4

0.09)

(0.4

0.09)

(0.4

0.09)

0.661

HYDRAULIC SYSTEM

A: Standard value

Unit: mm (in.)

Truck Models

1 ton class

2 ton class

3 ton class

Items

Rod outside diameter 1

25 (0.98)

30 (1.18)

35 (1.38)

Cylinder inside diameter 2

63 (2.48)

70 (2.76)

(3.15)

Cylinder outside diameter 3

73 (2.87)

82 (3.23)

93 (3.66)

Bushing inside diameter on head side 4

Bushing outside diameter on rod side 5

265

314

373

Tightening torque of guide bushing 6

(2713.0)

(38 13.7)

127

9.8

235

19.6

392

Tightening torque of nut 7

(13

1.0)

(24

2.0)

(40

2.5)

14.51

18.41

Tightening torque of tilt socket

153 to 182

Tilt

bolt 8

19)

cylinder

HYDRAULIC SYSTEM

Structure and Operation

Control Valve

P Pressure oil inflow port from pump

PF To steering control valve

Tl To

tank (return line)

T2 Return from steering control valve

: To lift cylinder

A2 To tilt cylinder rod end

: To tilt cylinder head end

Main valves

cover section (with built-in priority valve)

6 End cover section (with built-in

valve)

2 Lift valve (with built-in

regulator valve)

7 Steering system relief valve

3 Tilt valve

8 Main relief valve

4 Attachment valve

valve (with solenoid)

5 Attachment valve (2)

10 Lift lowering limit switch (if equipped)

The above illustration shows an external view of the

Lift valve 2 is a direction control valve which feeds and

four-valve type control valve. Any one of the

returns pressure oil to and from the lift cylinder. The

valve to five-valve type valves is installed on a truck

lift valve also has a built-in flow regulator valve.

depending on forklift specifications. The most basic

Tilt valve 3 feeds and returns pressure oil to and from

valve configuration is a two-valve type, combination of

the tilt cylinder which tilts the mast forward or

the lift and tilt. Adding attachment

to this

backward. The tilt lock valve is assembled in the main

combination is three-valve type, four-valve type or

spool to ensure safety when the mast is tilted forward.

valve type valve.

Attachment valves 4 and 5 are direction control valves

Inlet cover section 1 has a built-in priority valve. This

which feed pressure oil to actuators of the attachments.

valve is a flow divider valve which feeds a certain

End cover section 6 is provided with unloader valve 9.

amount of the total inflow volume from the port

This valve is linked with the seat switch, and is a

preferentially to the steering system and the extra flow

solenoid valve which closes the parallel feeder (high-

volume to the cargo-handling valve. In addition, the

pressure circuit) to hold pressure oil only when the seat

inlet cover section is provided with main relief valve 8

switch is ON.

and steering relief valve 7. Each of these valves limits

the maximum pressure to protect the system.

Lift valve 2 and tilt valve 3 are assembled adjacent to

the combination section.

HYDRAULIC SYSTEM

Hydraulic Circuit Diagram of Hydraulic Control Valve

For the entire diagram of the hydraulic

This diagram is for the three-valve type control valve. For the

system, refer to page 1

five-valve type control valve, the attachment valve 7 is added.

Priority valve

Main relief valve

Steering system relief valve

Lift valve

Solenoid valve (operates in

conjunction with lift lowering

switch)

Tilt valve

Attachment valve

Unloader valve

Solenoid for unloader valve

Center bypass port

Parallel feeder

P Supplied from pump

PF : To steering valve

T2 Return from steering valve

: To hydraulic tank

To lift cylinder

A2 : To tilt cylinder rod end

B2 : To tilt cylinder head end

A3 : To actuator for attachment valve

B3 To actuator for attachment valve

HYDRAULIC SYSTEM

Inlet

Section

PF restricted are

EF restricted area

xtra flow (EF flow)

Hole A

Priority flow (PF flow)

Ball check seat surfac

2097

Priority valve spool

: From hydraulic pump (pump port)

Spring

: To steering valve (priority port)

Ball check

EF : To cargo-handling valve (extra port)

Ball retainer

Damper chamber

Main relief valve

Steering system relief valve (PF relief valve)

Valve

The inlet section of control valve consists of main relief

When the flow volume flowing in the port P from the

valve 6, which limits the maximum pressure of the

pump increases, PF flow passing the control orifice is

hydraulic system, the priority valve, which feeds

going to increase. Then, differential pressure before and

pressure oil preferentially to the steering system, and

after the control orifice becomes greater.

steering system relief valve7, which limits the

On the left edge face of valve spool 1 acts hydraulic

maximum pressure of the supplied pressure oil.

pressure before the control orifice, namely pump

The priority valve is a flow divider valve which divides

pressure, and on the right edge face of the spool acts PF

supplied oil to a predetermined volume of priority flow

flow pressure. Therefore, when differential pressure

(PF flow) and extra flow (EF flow). PF flow and EF

becomes greater, the valve moves to the right, closes the

flow are supplied to the steering system and the

PF restricted area and opens the EF restricted area,

handling valves, respectively.

releasing extra flow to the EF port. As a result, PF flow

decreases and differential pressure also decreases. On

The above illustration shows a position of priority valve

the other hand, when the flow volume of pressure oil

spool 1 during operation (during pump rotation).

flowing in the port

decreases, PF flow flowing

The priority flow (PF flow) of pressure oil which flows

the control orifice decreases and differential

in the port P flows in the following sequence:

pressure also decreases. The spool moves to the left and

PF restricted area

Hole A

Control orifice

restricts extra flow. As a result, PF flow increases and

Groove between ball check 3 and ball retainer 4

differential pressure also increases. Differential

Spring chamber PF port.

pressure varies between extra flow and PF flow not only

This passage is always open and a certain volume of oil

is flowing toward the steering valve during operation.

Differential pressure before and after the control orifice,

however, can be kept constant by adjusting

of the

passes

port

of the load-handling valve.

1-46

HYDRAULIC SYSTEM

Valve 8 is an orifice provided in oil inflow and outflow

passages of damper valve 5. This orifice diverts

preferentially PF flow in a stable condition (no occurrence

of surging) by controlling the moving speed of valve spool

When extra flow (EF flow) is increased, pressure oil in the

ovement

valve

port flows in damper chamber 5. As the passage is the

orifice on the edge of valve 8 only, movement of valve

spool 1 is slow.

When PF flow is insufficient, it is necessary to increase PF

flow by quickly restricting the EF restricted area. For this,

When increasing extra flow

it is necessary to quickly discharge oil in damper chamber

5. As the orifice on the circumference as well as the orifice

on the valve edge is provided in the passage at this time,

the spool can move to the left quickly.

This action, when pressure of PF flow lowers, can prevent a

kickback phenomenon caused on the steering wheel.

Ball check 3 prevents

of PF flow. This is a

preventive measure for a kickback phenomenon.

When restricting extra flow

209742

Main Relief Valve

This valve is a relief valve with a pilot valve. When

pressure in the P port reaches the set value, poppet valve 1

is pushed to the left (in the illustration), leaving the seat.

Pilot oil in the spring chamber flows in the drain passage.

Then, dump valve 2 moves to the left, releasing a part or all

of main flow to the low-pressure passage. This is a safety

valve to protect the system. To adjust, turn adjusting screw

3 to change preload of spring 4.

Drain passage of

Spring chamber

pilot oil

209743

Steering System Relief Valve

Valve

relief valve)

This valve is a relief valve of direct-acting type, and acts

when the steering wheel is fully turned. This is a safety

valve to protect the system. To adjust, turn the adjusting

screw to change preload of the spring.

PF flow passage

209744

1-47

HYDRAULIC SYSTEM

Valve

passage for opening

load check valve

Center bypass port

209745

Main components

1 Lift spool

6 Solenoid valve

: Lift cylinder port

2 Valve body

7 Flow regulator valve

: Tank port

3 Return spring

8 Shut-off valve

4 Check valve

9 Roller for lift lowering limit

5 Load check valve

switch

The above illustration shows the lift control valve when

spool 1 is at the "neutral position."

Neutral position:

Spool 1 is placed at the "neutral position" by return spring

3 and oil in the

port is blocked by load check valve 5.

As the center bypass port is open, pressure oil flows into

the tilt valve without being blocked.

Ascending position of lift cylinder:

Spool moves to the right (as in the above illustration) and

blocks the center bypass port. Pressure in the parallel

feeder (high-pressure passage) rises and pressure oil pushes

open check valve 4, reaching load check valve 5.

Furthermore, pressure oil pushes open load check valve 5,

flows in the

port and in the bottom of the lift cylinder

piston. And it pushes the cylinder rod upward.

HYDRAULIC SYSTEM

Oil passage for opening load

check valve

Neutral

Center bypass port

Descending position of lift cylinder:

Action of flow regulator valve

The above illustration shows the lift control valve when

Restricted area

spool 1 is at "descending position."

Chamber C

Spring E

Spool

, pushed in body 2, is at the position as shown

Adjusting

in the illustration. The center bypass port is not

blocked. The secondary port of flow regulator valve 7

is open to the T2 port (return passage).

Prim

pres

When spool I is pushed in the body, roller 9 of the lift

lowering limit switch is pushed in, turning the switch

ON. The truck body controller (VCM-1) detects this

Secondary pressure

and feeds current to solenoid valve 6 to activate. When

the solenoid activates, pilot oil behind load check valve

The flow regulator valve keeps the maximum speed

5 is released to the passage

Thus, load check valve

constant during cylinder descent regardless of the load

5 moves to the left (in the illustration) by pressure of

weight on the fork.

the

port and oil in the A l port flows to the T2 port

Oil from the

port (primary pressure) passes through

via flow regulator valve 7.

the restricted area D and its pressure is reduced. This

Shut-off valve 8 forcibly opens load check valve 5 if

pressure-reduced oil (secondary pressure) flows to the

the load check valve does not automatically activate

chamber C through the orifice (b) and moves the valve

due to malfunction of solenoid 6 or any other reason.

spool to the right against the spring E, restricting the

Just loosen the lock nut and push in the screw.

restricted area D. The degree of this restriction is

greater as the primary pressure is higher. Thus, the

secondary pressure is made constant. If the secondary

pressure is constant, the outflow volume is constant.

The right part of this valve is a mechanism to stabilize

valve spool movement.

To adjust the flow volume, turn the adjusting screw.

However, do not adjust in field because it is difficult to

determine whether it is good or bad.

SYSTEM

Tilt Valve

tilt

Main components

1 Tilt spool

A2 To tilt cylinder rod

2 Return spring

B2 : To tilt cylinder head

3 Checkvalve

T2 Tank port (return passage)

4 Tilt lock valve

5 Tilt lock valve spring

6 Valve body

The above illustration shows the tilt control valve when

Mast backward tilt position:

spool 1 is at the "neutral position."

Spool 1 moves to the right. The B2 port is connected to

the T2 port and the A2 port is connected to passage A.

The spool is positioned to block the center bypass port,

Neutral position:

but as the spool is provided with a hole under the land,

Spool 1 is placed at the

position" by return

it does not block completely. This is designed to

spring 2, and both the A2 port and B2 port are blocked

prevent a large amount of oil from flowing at a time to

by the spool.

avoid abrupt movement of the cylinder, a characteristic

As the center bypass valve is open, oil in the bypass

of this valve. When the center bypass port is blocked,

port flows in the attachment valve.

pressure in the parallel feeder rises. Pressure oil pushes

open check valve 3, flows in passage A and flows to the

tilt cylinder rod from the A2 port. At the same time, oil

in the tilt cylinder head flows to the T2 passage. These

two actions pull the rod into the tilt cylinder.

HYDRAULIC SYSTEM

Mast forward tilt position:

port and "opening" of the return passage of the A2 port.

The above illustration shows the tilt control valve when

Tilt lock valve 4 does not operate unless the engine

spool 1 is at the "forward tilt position." Spool 1 is

runs and pressure oil is supplied from the pump. This

pushed into body 6. Then, the B2 port is connected to

valve is a kind of an anti-disaster valve.

passage A. At the same time the center bypass port is

blocked. This blockage, however, is not complete

because there is a hole under the land. This is designed

to prevent abrupt movement of the cylinder, a

characteristic of this valve. As the center bypass port is

blocked, pressure in the parallel feeder rises, pushing

open check valve 3 and pressure oil flows to passage A.

Oil in passage A flows to the tilt cylinder head from the

B2 port and acts to push out the cylinder rod. At the

same time, pressure oil in passage A flows to the

chamber on the right end of tilt lock valve 4 via orifice

(a) and pushes the tilt lock to the left against spring 5.

Then, return oil from the A2 port flows to the hole (b),

passage (c),orifice (d) and passage T2. The tilt cylinder

tilts forward due to pressure oil supplied from the B2

SYSTEM

Valve

1 Solenoid valve

2 Valve

Tank port (return passage)

Pilot

The above illustration shows the unloader valve when the engine

stops.

When the seat switch is

solenoid valve 1 is open and pilot

oil in the back of valve 2 is connected to the

passage.

Therefore, oil in the parallel feeder (high-pressure line) lightly

pushes up valve 2, flowing to the

port. Namely, as hydraulic

pressure cannot be held, the cylinder cannot be moved even if the

valve operating lever is moved.

When an operator sits on the seat, the seat switch is turned ON,

actuating solenoid valve 1 to block the pilot passage.

the

parallel feeder can hold oil pressure. This valve is an anti-disaster

valve.

SYSTEM

Removal and Installation of Control Valve

Removal and Installation

Removal

1. Remove the floor plate.

2. Remove the clevis pin of the control lever rod and

separate the rod from the control valve spool.

3. Disconnect each piping from the valve.

(1) Pump delivery hose

(2) Tilt pipe

(3) Lift pipe

(4) Return hose

(5) Supply pipe to steering valve

(6) Return hose from the steering valve

4. Separate the solenoid valve and harness of the

microswitch from the connector.

Tilt hoses

5. Remove valve mounting bolts and nuts (arrows in the

illustration on the right) and remove the valve.

Installation

To install, follow the reverse of removal sequence, and do

the following steps:

Control

Check the hydraulic oil level. Replenish it to the specified

level if the level is low.

hose

210112

HYDRAULIC SYSTEM

Disassembly and Reassembly

Valve of

Cover Section

Disassem y

209741

Sequence

Priority valve (1 thru 6)

Main relief valve (7)

1 Plug, O-ring

Steering system relief valve (8)

2 Spool assembly

IV. Other parts (9 and 10)

3 Spring

9 Plug, O-ring

4 Retainer

10 O-ring

5 Ball

6 Plug, O-ring

Suggestions for Disassembly

Note: When loosening the relief valve, apply a spanner

to the plug area of the relief valve to remove. If

Do not disassemble the main relief valve and the

the

nut is loosened by mistake, the set

relief valve of the steering system unless there is

pressure of the relief valve changes. If it is

any abnormality.

loosened by mistake, use a pressure gauge to

reset.

HYDRAULIC SYSTEM

Combination Section

Disassembly of Lift Valve

Sequence

I. Lift valve (1 thru 9)

9 Seal

1 Check valve, spring

Load check valve

thru 15)

2 Bolt

10 Plug, O-ring

3 Cap

11 Spring

4 Spool, return spring

12 Check valve

5 Plate

13 Solenoid valve

6 Seal

14 O-ring

7 Bolt

Shut-off valve

8 Plate

Flow regulator valve (16)

Suggestions for Disassembly

(1) Remove spool 4 from the combination valve body

When disassembling, make a record of the

with the return spring and cap screw attached.

protrusion amount of the set screw. Reassemble it

to the same dimension.

(2) When removing the cap screw, hold the spool in a

vise with soft jaws (hard wooden plate or plastic

(4) Do not, in principle, disassemble or adjust shut-off

plate) and remove the cap screw using a hexagon

valve 15. When disassembling, make a record of

wrench. Be careful of the spring jumping out.

the protrusion amount of the set screw. Reassemble

it to the same dimension.

(3) Do not, in principle, disassemble or adjust flow

regulator valve 16. If internal parts are damaged,

replace it as an assembly.

it as an

assembly without touching the adjusting screw and

lock nut.

11-55

HYDRAULIC SYSTEM

Disassembly of Tilt Valve

Sequence

Check valve, spring

Disassembly sequence of spool

Shut-off valve (15 and 16)

Bolt

sub-assembly

thru 14)

15 Shut-off valve on tilt cylinder

head

Cap screw

Spool sub-assembly

11 Spring retainer

16 Shut-off valve on tilt cylinder

Plate

12 Spring

rod

Seal

13 Spring

Bolt

14 Tilt lockvalve

Plate

Seal

Suggestions for Disassembly

(1) Remove spool 4 from the body with spring 12 and cap

screw 1 0 attached.

(2) When removing cap screw 1 0 , hold the spool in a vise

with soft jaws (hard wooden plate or plastic plate) and

remove the cap screw using a hexagon wrench. Be

careful of the spring jumping out. Remove also the tilt

lock valve.

HYDRAULIC SYSTEM

after Disassembly

Valve, spool and return spring

(1) Check the valve body for cracks, damaged sliding

surface and wear of check valve seat.

(2) Check the spool for damage, seizure, bend and

operating force.

(3) Check the tilt lock valve for damage and seizure.

203517

To reassemble, follow the reverse of disassembly sequence,

and do the following steps:

(1) Clean disassembled parts with an appropriate solvent.

Remove foreign matters with compressed air.

(2) Apply hydraulic oil to all parts.

(3) Replace O-rings.

(4) Tighten tie bolts.

Tighten tie bolts evenly. Tightening them unevenly or

torque can distort the valve body,

resulting in unsrnooth movement of the spool.

(5) Install component valves after appropriate valve bodies

are installed with tie bolts.

(6) Check that the spools slide smoothly.

Note: The valve body and spool have been lapped as a set.

Do not change the combination. When either one of

the two becomes necessary to replace, replace them

together as an assembly.

(7) Check that the

is in position. Adjust its

position if necessary.

MAST AND FORKS

Mast System

I 2.

and Function

I 2.

Simplex (Dual Panoramic) Mast

12.

Duplex (Dual Full-free Panoramic) Mast

12.

Triplex (Triple Full-free Panoramic) Mast

12.

Mast Operation

12.

I. Simplex Mast

12.

2. Duplex Mast

12 -

3. Triplex Mast

12 -

Removal

and installation

Mast and Lift Bracket Assembly

12 -

Simplex Mast

12 -

Duplex and Triplex Mast

12 -

Disassembly and Reassembly

Simplex Mast, Disassembly

12 - 12

Duplex Mast, Disassembly

12 - 14

Triplex Mast, Disassembly

12 - 16

Reassembly

12 - 19

1. Installing lift bracket rollers

12 - 19

2. Installing mast rollers

12 - 22

3. Installing mast strip

12 - 23

second lift cylinders

12 - 23

5. Installing first lift cylinders

12 - 24

6. Connecting chain

12 - 24

7. Installing hydraulic lines

12 - 25

Removal and Installation of Mast Rollers and Strips

without Removing Mast from Ruck

- 28

1. Simplex Mast

12 - 28

2 . Duplex Mast

12 - 29

3. Triplex Mast

12 - 30

MAST AND FORKS

Mast System

Following table shows a combination of truck and mast

models:

3 ton class

Note:

presents maximum lift height.

Example:

30: Lift Height of 3000 mm

Mast Serial Number Location

Mast Model Code

How to Read Mast Model Code

lifting height

stands for 3000 mm (1 18 in.)]

of the minor change

("A" for the original,

for the first change,

for the second change, and so on)

truck model designation (Example:

15: 1 ton class

25: 2 ton class

3 ton class

of mast

V: simplex mast

F: duplex mast

triplex mast

change

for the original,

for the first change, and so on up to

MAST AND FORKS

Structure and Function

(Dual Panoramic) Mast

Note: (1) Illustration shows

model.

(2) For hydraulic lines, refer to

Hydraulic Line" on the page

Major Components (most parts come in pairs, left and right)

1 Outer mast

9 Chain

17 Mast support cap

2 Inner mast

10 Lift bracket upper roller

18 Mast strip

3 Lift bracket

11 Lift bracket middle roller

19 Lift cylinder upper

4 Backrest

12 Lift bracket lower roller

mounting bolts

13 Side roller

20 Cylinder bracket

6 Tilt cylinder

14 Outer mast roller

21 Cylinder clamps

7 Lift cylinder

15 Inner mast roller

8 Chain wheel

16 Tilt cylinder, Tilt socket

mounting pin

Simplex mast features two lift cylinders placed behind

Lift cylinder 7 of a lift height of 3300 mm (130 in.) or

the mast columns, right and left, to provide maximum

less is equipped with down cushioning and no return

visibility.

hose by internal drain.

Mast strips are fitted to the top end of outer mast.

Lift cylinder of a lift height of 3500 mm (138 in.) or

These strips are for backing up the inner mast when the

more is equipped with drain hose.

mast is tilted backward.

For mast operation, refer to "Mast Operation" on page

12-5.

FORKS

Duplex (Dual Full-free Panoramic) Mast

5C to

Note: (1) Illustration shows

model.

(2) For hydraulic lines, refer to "Installing Hydraulic Line" on the page 12-26.

(3) For lift bracket, fork, and backrest, refer to "lllustration of Simplex Mast Structure."

Main parts are almost the same in models.

Major Components (most parts come in pairs, left and right)

1 Outer mast

6 Chain wheel

Mast support cap

2 Inner mast

7 Chain

Mast strips

3 Tilt cylinder

8 Outer mast roller

13 Lift cylinder upper

4 First lift cylinder (one piece)

9 Inner mast roller

mounting bolt

5 Second lift cylinder

10 Tilt cylinder,

14 Cylinder bracket

Tilt socket mounting pin

15 Cylinder clamp

In duplex mast, the first cylinder raises the forks

First cylinder is equipped with upstroke cushioning

without increasing the overall mast height (free-lift)

with internal drain and second cylinder equipped with

until the upper edge of the backrest exceeds the top of

down cushioning.

the mast.

For mast operation, refer to "Mast Operation" on page

The mast assembly consists of the inner mast, outer

12-5.

mast, lift bracket, first lift cylinder and second lift

cylinders.

The first lift cylinder raises the lift bracket, while the

second cylinders operate the inner mast and lift bracket.

MAST AND FORKS

Triplex (Triple Full-free Panoramic) Mast

Note: (1) Illustration shows

model.

(2) For hydraulic lines, refer to

Hydraulic Line" on the page 12-27.

(3) For lift bracket, fork, and backrest, refer to "Illustration of Simplex Mast Structure."

Main parts are almost the same in all models.

Major Components (most parts come in pairs, left and right)

1 Outer mast

10 Second lift chain

17 Tilt cylinder, tilt socket

2 Middle mast

11 Hose pulley

mounting pin

mast

12 Chain guard

18 Mast support cap

4 Tilt cylinder

(Right or left type)

19 Maststrips

5 First lift cylinder (one piece)

13 Outer mast roller

20 Lift cylinder upper

6 Second lift cylinder

14 Middle mast upper roller

mounting bolt

7 First lift chain wheel

15 Middle mast lower roller

21 Cylinder bracket

8 Second lift chain wheel

16 Inner mast roller

22 Cylinder clamps

First lift chain

In triplex mast, the free-lift height extends to the top of

First cylinder is equipped with upstroke cushioning and

the mast, and the overall mast height remains the same

second cylinder equipped with down cushioning and

until the upper edge of the backrest exceeds the top of

both cylinders have no return hose by internal drain.

the mast.

For mast operation, refer to "Mast Operation" on page

The mast assembly consists of the inner mast, middle

12-5.

mast, outer mast,

bracket, first lift cylinder and

second lift cylinders.

The first lift cylinder raises the lift bracket, while the

second cylinder operates the three-stage telescopic

mechanism and lift bracket.

12-4

MAST

FORKS

Mast Operation

1. Operation of Simplex Mast

Operation of Mast

The lift cylinders extend, which lifts the forks until the

maximum free-lift height is reached.

The cylinders extend further, causing the inner mast to

lift at the same speed as the rods while at the same time

causing the forks to lift at the speed twice as fast as the

Lift

inner mast.

cylinder

Outer

mast

Forks on

Maximum

the ground

free lift

lift

205371

2. Operation of Duplex Mast

Operation Mast

The first lift cylinders extend, bringing the forks to the

maximum free-lift height.

When the first lift cylinder rods have reached the end of

the stroke, the second lift cylinders take over to directly

Second

lift the inner mast to the maximum lift height.

cylinder

The lowering mechanism is the reverse of lifting.

Outer

mast

Forks on the

Maximum

ground

free lift

lift

205372

3. Operation of Triplex Mast

Operation of Mast

First lift

The first lift cylinders extend, bringing the forks to the

chain

free-lift height.

Fir

lift

mast

When the first lift cylinder rods have reached the end of

the stroke, the second lift cylinders take over to lift the

Second

lift chain

middle mast while at the same time the second lift chain

lifts an assembly of the forks, inner mast and first lift

Second lift

cylinders.

cylinder

Outer mast

The lowering process takes place in the reverse order of

lifting.

Forks on the Maximum

Maximum

ground

free lift

lift

205374

MAST AND FORKS

and

Note: For replacing mast roller without removing mast

from track, refer to page 12-28.

Mast and Lift Bracket Assembly

Simplex Mast Removal

Sequence

1 Nuts

5 Tilt socket pin

2 Backrest, Lift bracket, Forks

6 Mast support bearing cap, Bushing

3 Return hose (hi-lift model)

7 Inner mast, Outer mast, Lift cylinder

4 High-pressure hose

Suggestions for Removal

1. Removing lift bracket

Tilt the mast forward, and lower the inner mast to

the bottom. Slacken the lift chains, and remove the

nuts from the anchor bolts.

(2) Tilt the mast back to vertical position. Raise the

inner mast until the lift bracket 2 becomes free.

Then, slowly back the truck away, from the lift

bracket and fork assembly.

Note: Before proceeding any mast overhaul, measure

the clearance between mast and rollers.

Knowing which roller should be replaced or

which shims need adjustment in advance allows

efficient maintenance work.

MAST AND FORKS

2. Disconnecting return hose for lift cylinder

To right lift cylinder

(For high-lift cylinder model)

(1) Start the engine and raise the mast in the highest

Return connector

position.

(2) Stop the engine and disconnect the hose 3 at the hose

(Allow) of return connector.

(3) Lower the mast.

3. Disconnecting high-pressure hoses for lift cylinder

Place the mast in the bottom position, disconnect the hose 4

To left lift cylinder

at the arrow position in the illustration on the previous

204874

4. Separating tilt cylinders

(1) Hitch a sling to the upper cross-member of the outer

mast, then lift with a hoist.

Be sure to use a hoist having a capacity enough

to support the mast assembly.

(2) Place wood blocks under the tilt cylinder mounting

section and remove the tilt socket pins, and separate the

mast from the tilt cylinders.

(3) Start the engine, and pull back the tilt lever to retract

the tilt cylinder rods.

the engine is running.

Never loosen ti

MAST AND FORKS

5. Removing mast support bearing caps

Mark caps to ensure the caps are reinstalled in original

positions during reassembly.

(2) Remove cap mounting bolts. Dismount the mast

assembly from truck in the suspended condition. With

the lift bracket side facing up, place the mast assembly

horizontally on wooden blocks on a level ground.

Note: Lay the mast assembly on a space large enough to

disassemble the parts.

Installation

To install, follow the removal sequence in reverse with

followings in mind.

1. Mast Support

lnner bushing lnner cap

(1) Apply grease to the inner surfaces of caps and mast

support bushings.

(2)-a 1 ton class:

When installing caps, make sure the wider chamfered

side faces toward the center of the chassis.

(2)-b 2,3ton classes:

Chamfering is the same both in the right and left

bushing

sides. Be sure to reassemble in the same position as it

was.

(3) When applying grease, place wood blocks under the

1 ton class

mast. By doing so, it is easily greased.

2. Adjust the chain tensions

Refer to the "Chain Tension Adjustment

3. Bleeding lift cylinders

Start the engine, raise and lower the lift bracket with

several strokes to bleed the cylinder.

After proper operation is confirmed, check the oil level in

hydraulic tank.

2, 3 ton classes

MAST AND FORKS

Duplex Mast and Triplex Mast Removal

Note: For replacing

roller without removing mast

from track, refer to page 12-29 or 12-30.

Illustration shows triplex mast.

209732

Sequence

1 Nuts

4 Tilt socket pin

2 Backrest, Lift bracket, Fork

5 Mast support bearing cap, Bushing

3 High-pressure hose

6 Mast, Lift cylinders

Suggestions for Removal

Removing lift bracket

Lower lift bracket, and place wood blocks under

the assembly. Tilt the mast forward, lower the

inner mast to the bottom, then remove nuts 1 from

the anchor bolts of the first lift chains.

(2) Tilt the mast back to vertical position. Raise the

inner mast until main rollers of the lift bracket

become free. Then, back the truck away, from the

lift bracket.

Note: Before proceeding any mast overhaul, be sure to

measure the clearance between mast and rollers.

Knowing which roller should be replaced or

which

need adjustment in advance allows

efficient maintenance work.

MAST AND FORKS

2. Disconnecting high-pressure hoses for lift

cylinder

Place the mast in the bottom position, disconnect the hose 3

at the arrow position in the illustration on the previous

3. Separating tilt cylinders

(1) Hitch a sling to the upper cross-member of the outer

mast, then lift with a hoist.

Be sure to use a hoist having a capacity enough

to support the mast assembly.

(2)

wood blocks under the tilt cylinder mounting

section and remove the tilt socket pins, and separate the

mast from the tilt cylinders.

(3) Start the engine, and pull back the tilt lever to retract.

Do not touch any levers except the tilt lever while

the engine is running.

Never loosen

socket bolts except for tilt

cylinder disassembling.

Removing mast

bearing caps

Mark caps to ensure the caps are reinstalled in original

positions during reassembly.

Remove cap mounting bolts. Dismount the

assembly from truck in the suspended condition. With

the lift bracket side facing up, place the mast assembly

horizontally on wooden blocks on the level ground.

Match marks

te: Lay the mast assembly on a space large enough to

207615

the parts.

MAST AND FORKS

To install, follow the removal sequence in reverse with

followings in mind.

1. Mast Support

lnner bushing lnner cap

(1) Apply grease to inner surfaces of caps and mast

support bushings.

(2)-a 1 ton class:

When installing caps, make sure the wider chamfered

side faces toward the center of the chassis.

(2)-b 2 , 3 ton classes:

Chamfering is the same both in the right and left

sides. Be sure to reassemble in the same position as it

bushing

was.

(3) When applying grease, place wood blocks under the

1 ton class

mast. By doing so, it is easily greased.

2. Adjust the chain tensions

Refer to the "Chain Tension Adjustment."

3. Bleeding lift cylinders

In the duplex mast, the second lift cylinders are provided

with air bleeding screws.

After installing the mast, start the engine, raise and lower

the lift bracket with several strokes and loosen the screws

to bleed.

In the triplex mast, no air bleeding screws are provided.

ton classes

Raise and lower the lift bracket with several strokes to

bleed the air trapped below the piston.

After proper operation is confirmed, check the oil level in

hydraulic tank.

FORKS

Disassembly and Reassembly

Simplex Mast

Disassembly

Sequence

1 Nuts

11 Chain wheel

2 Forks, Lift bracket

12 Cylinder clamps, Seats, Shims, Cushion,

3 Backrest

Collar, Bolts

4 Lift bracket upper, Lower rollers

13 Bolt, Shims

5 Lift bracket lower rollers

14 Mast strips, Shims

6 Lift bracket side rollers

15 Outer mast main rollers

Chain

16 Inner mast main rollers

guard

17 Inner mast

9 Lift hose (high pressure), Rubber hose,

18 Lift cylinders

T-joint, Down safety valve

19 Outer mast

10 Return hose (high lift mast)

Suggestions for Removal

Removing mast strips and main rollers

bolts 12, 13 to free lift cylinder 18.

Displace the tops of the two lift cylinders from

inner mast 17. Slide inner mast toward the bottom

of outer mast 19, and remove main rollers 15, 16

and mast strips 14.

MAST AND FORKS

mast removal

After removing the main rollers, hitch a sling to the inner

mast cross-member and slide the inner mast to the upper

side of the outer

to clear the outer mast roller shafts.

Hitch a sling to the inner mast again and remove it from the

outer mast.

Inspection after disassembly (all models)

Mast

Check each roller for wear, binding or other defects.

(2) Check each roller on rolling surface for pitting or other

defects.

(3) Check the mast member and the welded joints of

members, shafts and supports for cracks.

(4) Check the mast support bushings for wear or other

defects.

207090

2. Lift bracket

Check the main rollers and side rollers for smooth

rotation. Inspect each roller for wear and cracks.

(2) Check the welded portions of the bracket for cracks.

(3) Check the finger bar for bend or distortion.

A: Standard value

5 mm (0.2 in.)

Distortion of finger bar

Chain elongation

3. Lift chains, chain wheels and chain wheel supports

A: Standard value B: Repair or service limit

(1) Measure the length of each chain to make sure that two

Unit : mm

links

chains are equal in length. Also check the chains for

wear, indication of breakage, link binding and twist.

(2) Check each chain anchor bolt for cracks or defects on

thread.

(3) Check each chain wheel support and chain wheel for

crack or wear. Check that the wheels rotate smoothly.

4. Mast strips

Check the mast strips for damage, wear or distortion.

MAST AND FORKS

Duplex Mast

Disassembly

Sequence

Lift hose (high pressure), Clamp

Mast strips, Shims

Shims, Bolts, Washers

Mast Rollers

First lift cylinder

Stopper cushion, Cushion plate, Shim, Bolt,

Chain guard

Washer

Chain wheel support, Pin

Inner mast

Chain wheels, Snap rings

Second lift cylinders

Hose guard, Bolt, Washer

Cylinder brackets

High-pressure hose

O-rings, Plugs

Seats, Shims, Cushions, Collars

Outer mast, Grease nipples

Bolts, Washers, Shims

Note: The lift bracket disassembly procedure is the

same as for the simplex mast.

MAST AND FORKS

Start by:

(a) With the lift bracket facing up, place the mast

horizontally on wood blocks. Place a wood block as a

wedge to prevent the inner and middle masts from

sliding.

(b) Before disassembling the mast and fork assembly,

measure and record all clearances between each lift

bracket and roller and between each mast and roller.

Recorded measurements will be helpful when replacing

rollers or selecting shims to adjust clearances.

Suggestions for Disassembly

1. Removing first lift cylinder 4

Remove retaining bolts 2 from the first lift cylinder

(2) Hitch slings on first lift cylinder, and gently remove the

cylinder.

Use two slings. Wind or tie slings securely to prevent

slipping.

2. Removing main rollers 12 and mast strips

(I) Remove clamp bolts 9 from the second lift cylinders.

(2) Remove bolts

from the upper rod sections of the

second lift cylinders, and place the cylinders on the

outer mast.

(3) Check the number of shims and the shim thickness at

the rod end sections.

(4) Lower the inner mast, then remove main rollers 12 and

mast strips 1 .

3. Removing inner mast 14

Using slings, lift and remove inner mast 14, steering it

clear of the roller shaft sections of outer mast 18.

inspection after disassembly

Follow the same inspection procedure as for the simplex

mast.

MAST AND FORKS

Triplex Mast

Disassembly

Sequence

1 Hose for first lift cylinder, Clamp, Bolt, Washer

Snap rings, Chain wheels

2 Bolts, Washers

Snap rings, Hose pulleys, Shafts, Snap rings,

3 Shims

Chain wheels

4 First lift cylinder

Hose guard, Bolt, Washer

5 Chain guard

Hose, Clamp, Bolt, Washer

6 Chain wheel support, Pin

Joint, Connector, Bolt, Washer

7 Snap rings, Chain wheels

Bolts, Seats, Cushions, Collars

8 Nuts (chain for second lift cylinder)

Cushions, Shims, Bracket

9 Mast strips, Shims

Bolts, Washers, Shims

10 Main rollers, Shims

Second lift cylinders

Main rollers, Shims

Mast strips, Shims

12 Inner mast

Main rollers, Shims

13 Nuts

Main rollers, Shims

14 Lift chains (for second lift cylinders)

Middle mast

15 Chain guards, Bolts, Washers

Outer mast, Grease nipples

MAST AND FORKS

Note: The lift bracket disassembly procedure is the same

as for the simplex mast.

Start by:

(a) With the lift bracket facing up, place the mast

horizontally on wood blocks. Place a wood block as a

wedge to prevent the inner and middle masts from

sliding.

(b) Before disassembling the mast and fork assembly,

measure and record all clearances between each lift

bracket and roller and between each mast and roller.

Recorded measurements will be helpful when replacing

rollers or selecting shims to adjust clearances.

Suggestions for Disassembly

1. Removing first lift cylinder 4

(1) Remove retaining bolts

the first lift cylinder.

(2) Hitch slings on the cylinder, and gently remove the

cylinder.

Use two slings. Wind or tie slings securely to prevent

slipping.

2. Removing inner mast 12 and main rollers 10, 11

Lower inner mast 12 until the main rollers 10, 11 can be

removed. Remove the rollers and mast strips 9.

MAST AND FORKS

Follow the disassembly sequence in reverse. Be careful

with the followings .

Suggestions for Reassembly

Installing lift bracket rollers (all mast models)

No shim required

clearance

Upper

Middle roller

Side roller

Sequence

1 Lift bracket

3 Lift bracket middle rollers

5 Side rollers

2 Lift bracket upper rollers

4 Lift bracket lower rollers

Inner mast

The lift bracket has three main roller bearings at one

Clearance F

side and a side roller at both sides as shown.

Clearance between roller circumference and inner mast

Clearances F and G must be maintained between these

thrust surface (back-to-front play):

rollers and thrust surface of the inner mast for smooth

Clearance F is used for determining the proper size of

operation.

the rollers.

Select appropriate diameter rollers so that the clearance

Clearance G

meets the specification. Make sure the rollers rotate

Clearance between roller side surface and inner mast

smoothly when installed.

thrust surface (right-to-left-play).

Clearance G is used for determining the correct amount

Clearance

1 mm (0.04 in.) or less

of shims at the bearing seat.

Move lift bracket to the top of the inner mast and press

the bracket to either the left most or rightmost position.

Clearance

measurements of clearance G between the side

Clearance between side roller circumference and inner

surface of roller and inner mast.

mast side roller thrust surface:

Move side roller to the upper end of the inner mast and

Note: It is not necessary to adjust the lift bracket upper

press the lift bracket to either the left most or rightmost

roller with shims.

position.

Take measurement of clearance GI between the roller

Adjust the clearance to the specification with shims (a)

circumference and inner mast.

and (b) for middle roller and with shim (d) for the lower

Adjust the clearance with shims to the specification.

roller.

Clearance GI

0.1 to 0.5 mm (0.004 to 0.020 in.)

Clearance G

0.1 to 0.5 mm (0.004 to 0.020 in.)

MAST AND FORKS

(1) Choosing correct roller diameters

Unit : mm (in.)

Measure clearance for upper rollers 2, middle rollers 3

and lower rollers 4. If the measured clearances do not

conform to the standard values, replace with rollers of

correct diameters listed in the table to the right.

Note: For measuring procedures, refer to "Inspection and

Adjustment

The rollers installed should rotate smoothly.

(2) Adjusting clearance G between the middle roller and

Lift bracket middle roller

thrust plate

Note: The following adjustment is not required for the

upper roller.

Lift bracket

Measure clearance G between the middle roller and

thrust plate. If the measured clearance does not conform

to the standard value, adjust clearance G in the manner

Shim

described below.

Shim

Note: For measuring procedures, refer to "Inspection and

Adjustment

in.)

Adjustment

If clearance G is excessive, increase the thickness of shims

(a) as required. Increase the thickness of shims (b) by the

same amount that are added to shims (a).

Shim (a) is available in two sizes: 1 mm (0.04 in.) and 0.5

mm (0.020 in.). Shim (b) is available in only one size, 1

mm (0.04 in .).

If shims (a) are increased by 0.5 mm (0.020 in.), shims (b)

do not need to be increased by the equal amount.

Remarks: At the assembly plant, shims (a) are usually

adjusted to 1 mm (0.04 in.) and shims (b) to 2.0

mm (0.08 in.) for the shipment.

(3) Adjusting clearance G between lower rollers and inner

Lift bracket lower roller

mast

Measure clearance between the lower rollers and inner

mast

mast. If the measured clearance does not conform to the

standard value, adjust clearance

in the manner

0.1 to 0.5 mm

described below.

Note: For measuring procedures, refer to "Inspection and

Adjustment

If clearance G is excessive, increase the thickness of shims

as required.

Remarks: At the assembly plant, shims (c) are usually

adjusted to 1

(0.04 in.) for the shipment.

MAST AND FORKS

(4) Installing main rollers

To install main rollers on shafts, use a driving tool. Be

not to strike the outer roller surface with the driving

tool.

The side of the roller with larger chamfering must face

toward the outside.

Make sure the rollers rotate smoothly when installed.

(5) Adjusting clearance GI between the side roller and

inner mast

Lift bracket

Measure clearance GI between the side roller's rolling

mast

contact surface and inner mast. If the measured clearance

does not conform to the standard value, adjust clearance

GI in the manner described below.

roller

Note: For measuring procedures, refer to "Inspection and

Adjustment

bracket

If clearance G I is excessive, increase the thickness of

shims (d) as required.

Remarks: At the assembly plant, shims (d) are usually

adjusted to 1 mm (0.04 in.) for the shipment.

Cat Lift Trucks. For use with K21/K25 and S4S Engine Service Manuals (2007) - page 3