JLG 680S, Service And Maintenance Manual

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SECTION 3 - CHASSIS & TURNTABLE
3121234 3-65
26. Remove pistons (44) and slipper retainer (45) from the
cylinder block (46).
NOTE: The pistons are not selectively fitted, however units with
high hourly usage may develop wear patterns. Number the
pistons and bores for reassembly if they are to be reused.
27. Remove the ball guide (47), hold-down pins (48) and
retaining ring (49) from the cylinder block.
NOTE: Most repairs do not require block spring removal. Perform
this procedure only if you suspect problems with the block
spring.
RISK OF PERSONAL INJURY: COMPRESSING THE BLOCK SPRING REQUIRES
FORCE OF ABOUT 80 TO 90 LBF (350 TO 400 N). USE A PRESS SUFFICIENT TO
MAINTAIN THIS FORCE WITH REASONABLE EFFORT. ENSURE THE SPRING IS
SECURE BEFORE ATTEMPTING TO REMOVE THE SPIRAL RETAINING RING.
RELEASE THE PRESSURE SLOWLY AFTER THE RETAINING RING IS REMOVED.
28. Turn the block over. Using a press, apply pressure on the
block spring washer (50) to compress the block spring.
Compress the spring enough to safely remove the spiral
retaining ring (51). While maintaining pressure, unwind
the spiral retaining ring (51). Carefully release the pres-
sure and remove the outer block spring washer (50),
block spring (52) and inner block spring washer (53)
from the cylinder block.
Inspection
After disassembly, wash all parts (including the end-cap and
housing) thoroughly with clean solvent and allow to air dry.
Blow out oil passages in the housing and end cap with com-
pressed air. Conduct inspection in a clean area and keep all
parts free from contamination. Clean and dry parts again after
any rework or resurfacing.
PISTON
Inspect the pistons for damage and discoloration. Discolored
pistons may indicate excessive heat; do not reuse.
SLIPPERS
Inspect the running surface of the slippers. Replace any piston
assemblies with scored or excessively rounded slipper edges.
Measure the slipper foot thickness. Replace any piston assem-
blies with excessively worn slippers. Check the slipper axial
end-play. Replace any piston assemblies with excessive end-
play.
Minimum slipper foot thickness and maximum axial end-play
are given in the table below.
51
50
52
53
46
49
48
47
45
44
44. Piston
45. Slipper Retainer
46. Cylinder Block
47. Ball Guide
48. Holddown Pins 49. Retaining Ring
50. Block Spring Washer
51. Spiral Retaining Ring
52. Block Spring
53. Inner Block Spring Washer
Figure 3-47. Cylinder Kit Disassembly
Table 3-3. Slipper Foot Thickness & End Play
Measurement
L Frame
mm (in.)
K Frame
mm (in.)
Slipper Foot Thickness 2.71
(0.11)
4.07
(0.16)
Piston/Slipper End Play
0.15
(0.006)
Slipper
Maximum end play
M inimum
slipper fo ot
thick ness