JLG 4394RT Service Manual - Manual (Page 88)

SECTION 3 - CHASSIS, PLATFORM & SCISSOR ARMS
3-52 – JLG Lift – 3121249
SERVO PISTON AND MINIMUM ANGLE STOP
Inspect the minimum angle stop, servo piston head, and
servo piston ball-socket for damage or excessive wear.
Replace if necessary.
LOOP FLUSHING SPOOL
Inspect the loop flushing spool. Check for cracks or dam-
age. Replace if necessary.
Assembly
1. Install new O-ring (1) and piston seal (2) to the servo
piston (3). Install the piston seal over the O-ring.
Installing the piston seal stretches it, making it diffi-
cult to install the servo piston in its bore. Allow 30
minutes for the seal to relax after installation. To
speed up seal relaxation, compress the seal by
installing the piston head into the servo cavity in the
end-cap and let it stand for at least five minutes.
2. After piston seal has relaxed, lubricate and install
servo piston into the housing bore. Align the piston
with the ball socket facing the inside of the housing.
RISK OF PERSONAL INJURY: COMPRESSING THE BLOCK
SPRING REQUIRES ABOUT 80 TO 90 LBF (350 TO 400 N) OF
FORCE. USE A PRESS SUFFICIENT TO MAINTAIN THIS FORCE
WITH REASONABLE EFFORT. ENSURE THE SPRING IS SECURE
BEFORE ATTEMPTING TO INSTALL THE SPIRAL RETAINING
RING. RELEASE THE PRESSURE SLOWLY AFTER THE RETAIN-
ING RING IS INSTALLED.
3
2
1
3
1. O-ring
2. Piston Seal
3. Servo Piston
Figure 3-21. Servo Piston