Loader Bobcat 773. Instruction - page 42

HYDROSTATIC DRIVE MOTOR (Cont’d)

Disassembly And Assembly (S/N 509639898 & Below
& S/N 509616504 & Below ) (Cont’d)

Remove the O–rings inside the bore of the mounting
flange [A].

The bushing is a guide to center the motor on the
gearcase. If the bushing needs replacing, use the
following procedure:

Drill several holes in the bushing [B].

Use a chisel and hammer, remove the bushing from the
mounting flange [C].

Use a hydraulic press to install the new bushing.

Assembly: When installing the balance plate in the end
housing, put your finger through the hole and hold it in
position until the housing and balance plate is in position
[D].

NOTE: Always use new O–rings, gaskets and seals

when assembling the hydrostatic motor.

D

B–08690

A

B–04636

C

B–09470

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Service Manual

B

B–09469

HYDROSTATIC DRIVE MOTOR (Cont’d)

Inspection (S/N 509639898 & Below & S/N 509616504
& Below)

Clean all the parts in solvent and use air pressure to dry
them. DO NOT use cloth or paper because small pieces
of material can get into the system and cause damage.

Before the motor is assembled, check the following items:

Check the geroler rollers and rotor for wear and scratches
[A].

NOTE: Put all the rollers back in their original

position.

Check the valve plate for scratches [B].

Check the balance plate for scratches [C].

Check the valve drive and the main drive for wear.

Check the end plate surface for scratches [D].

A

B–06394

B–06392

C

B–06389

D

B–06388

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Service Manual

B

B–06391

B–06390

HYDROSTATIC DRIVE MOTOR (Cont’d)

Timing the Hydrostatic Motor (S/N 509639898 &
Below & S/N 509616504 & Below)

The timing of the motor controls the direction of rotation
of the drive shaft of the motor. The timing parts are as
follows:

1. Geroler (Item 1) [A].

2. Valve Drive (Item 2) [A].

3. Valve Plate (Item 3) [A].

4. Valve (Item 4) [A].

Find the largest opening between the geroler star and the
geroler ring and mark the outside of the geroler ring at that
point [A].

Align the two drain holes and the three pressure holes in
the geroler ring with the same holes in the mounting
flange and install the geroler assembly.

Install new O–rings.

Install the valve drive [A].

Align the drain hole in the valve plate with the drain hole
in the geroler. Install the valve plate with the O–ring
toward the geroler. Make sure the slot opening of the
valve plate is in alignment with the largest opening of the
geroler.

Install the valve plate.

Install the valve on the valve plate. Make alignment with
one of the side openings with the mark on the geroler.
Turn the valve clockwise a small amount until the teeth on
the valve drive engage.

Continue with the rest of the assembly procedure.

A

C–02384

4

2

3

1

Largest Opening

Pressure

Relief Hole (3)

Geroler

Ring

Geroler

Star

Valve Drive

Valve Plate

Case Drain

Hole (2)

Valve

Anyone of 6 Ports

Open to Outside of Valve

Rotate Valve Clockwise

1/2 Tooth to Engage Spline

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773 BICS Loader

Service Manual

Ref.

Description

Ref.

Description

1.

HOUSING

15.

SHAFT, drive

2.

O–RING

16.

BOLT

3

SEAL, square

17.

SPRING

4.

VALVE, plate

18.

PISTON

5.

GEROLER

19.

POPPET

6.

BALL

20.

SLEEVE

7.

PLATE, balance

21.

PLUG

8.

RING, back–up

22.

O–RING

9.

SEAL

23.

O–RING

10.

RING, back–up

24.

SPRING

11.

O–RING

25.

SHIM

12.

PLUG

26.

POPPET

13.

FLANGE, mounting

14.

SEAL, face

D–03431

HYDROSTATIC MOTOR 30 SERIES

Parts Identification – (S/N 509639899 & Above & S/N 509616505 & Above)

3

14

10

11

9

8

13

4

3

5

15

43

7

21

22

20

17

19

18

19

17 20

3

16

12

23

25

26

2

24

1

6

6

3

773 BICS Loader

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Service Manual

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