JLG sky trak mmv Service Manual page 401

b. Main Control Valve Disassembly
This section covers disassembly of one half (1) of the
main control valve, including the frame sway (2), attach-
ment tilt (3) and end cap (4) sections of the main control
valve.
1. To disassemble the frame sway, attachment tilt and
end cap sections of the main control valve (1),
remove the nuts (5 and 6) from the end of the tie
rods (7 and 8). The tie rods can remain in place in
the sections.
2. Disassemble each section assembly as required.
Some sections include a pre-adjusted relief valve that
regulates pressure in a specific circuit.
IMPORTANT: DO NOT adjust any of the relief valve
assemblies! Tampering with a relief valve will irrevocably
alter pressure in the affected circuit, requiring re-calibration
or a new relief valve.
Disassemble the End Cap Section
1. Carefully separate the end cap section (4) from the
attachment tilt section (3). Avoid dislodging or losing the
spring (9) and poppet (10).
2. Remove the o-ring (11) from between the two
sections.
3. Remove the shut-off plug (12) and o-ring (13) from
the end cap section (4).
Disassemble the Attachment Tilt Section
1. Carefully separate the attachment tilt section (3) from
the frame sway section (2). Avoid dislodging or losing
the shuttle (14), spring (15) and poppet (16).
2. Remove the o-ring (17) from between the two
sections.
3. Remove the spring (9) and poppet (10) from the
attachment tilt section (3).
4. Remove both socket head capscrews (18) securing
the end mechanism (19) to the attachment tilt
section (3).
5. Remove the retainer (20), spool cap (21) and
o-ring (22) from the end mechanism (19).
6. Remove both socket head capscrews (23) securing
the other end mechanism (24) to the attachment tilt
section (3).
7. Remove the retainer (25) and spool cap (26).
8. Hold the spool from turning while removing the spool
end (27) from the spool.
Model MMV Rev. 12/04
9. Remove the spring seat (28), spring (29), another
spring seat (28), small o-ring (30), large o-ring (31),
spool cap retainer (32) and o-ring (33) from this end
mechanism (24).
Disassemble the Relief Valve
The relief valve assemblies (34) are part of the attach-
ment tilt section. The valves are preset at 4000 ±50 psi
(276 ±3,5 bar).
Note: The internal parts of the relief valve can be disas-
sembled without removing the relief valve body ( 36 ) from
the valve section. Skip to step 2 to start disassembly of
the relief valve.
1. Remove the relief valve (34) and o-ring (35) from the
attachment tilt section assembly (3).
2. Grip the relief valve body (36) with a suitable tool
and use another tool to remove the nut (37),
revealing an o-ring (38) and the adjustment
screw (39).
3. Carefully remove the plug (40), spring (41) and pilot
poppet (42).
4. Remove the large o-ring (43), back-up ring (44),
small o-ring (45), large spring (46), small spring (47),
piston (48), o-ring (49), back-up ring (50) and relief
valve poppets (51 and 52).
Disassemble the Frame Sway Section
1. Carefully separate the frame sway section (2) from
the mid-inlet section (53). Remove the o-ring (54)
from between the two sections. Remove the shuttle
(14), spring (15) and poppet (16) from the frame
sway section (2).
2. Remove both socket head capscrews (18) securing
the end mechanism (19) to the frame sway section
(2).
3. Remove the retainer (20), spool cap (21) and
o-ring (22) from the end mechanism (19).
4. Remove both socket head capscrews (23) securing
the other end mechanism (24) to the frame sway
section (2).
5. Remove the retainer (25) and spool cap (26)
6. Hold the spool from turning while removing the spool
end (27) from the spool.
7. Remove the spring seat (28), spring (29), another
spring seat (28), small o-ring (30), large o-ring (31),
spool cap retainer (32) and o-ring (33) from this end
mechanism (24).
Hydraulic System
9.103