JLG 19AMI (3120758) Service Manual - Manual (Page 44)

SECTION 2 - SERVICE PROCEDURES
2-30 – JLG Lift – 3120758
2.12 MAST TO BASE FRAME INSTALLATION
1. Using an overhead crane or suitable lifting device
capable of supporting the weight of base frame,
attach a sling strap or chain to the front crossmem-
ber of the base frame, raise base frame.
2. Extend hydraulic cylinder out from bottom of mast
assembly approximately one (1) foot. (Caps on
extend and return ports will need to be removed to
extend cylinder. Catch any hydraulic fluid expelled
from return port in a container to prevent spillage
onto work area).
3. Bring base frame into position in front of mast
assembly, (base frame and mast assembly must be
held at 90° angle to each other).
4. Slide port end of hydraulic cylinder through hole in
base frame cylinder mounting channel. (Return port
(tube side) of cylinder must be on right side facing
bottom of base and mast).
5. Align threaded hole in side of hydraulic cylinder
head with hole in tab on bottom side of cylinder
mounting channel. Secure hydraulic cylinder to cyl-
inder mounting channel tab using a 5/16"-18UNC x
5/8" long hex head bolt and flat washer.
6. Carefully push mast assembly and base assembly
together until the four (4) holes on bottom rear of
mast align with holes in the base frame mast support
crossmember.
7. Attach mast to base using four (4) 3/8"-16UNC x 1"
long hex head bolts, locknuts and flatwashers,
(place a flatwasher under bolt head and nut and
mount with nuts on inside of frame).
8. Locate the two (2) mast support braces, attach to
sides of base frame using a 3/8"-16UNC x 1" long
hex head bolt, nut and flatwashers each brace,
(place a flatwasher under bolt head and nut and
mount with nuts on inside of frame. Use access hole
in bottom of frame to attach nut inside frame).
9. Before setting machine upright on base, install a
short 90° elbow fitting, flow control valve and
another short 90° elbow fitting on the end of the flow
control valve in the extend (left) port on bottom of
hydraulic cylinder. Install a long 90° elbow fitting on
return (right) port. Use sealant tape on fitting
threads. Cap ports until hydraulic lines are installed.
10. Carefully set machine in an upright position on its
base frame wheels.
11. Locate the mast support bracket. Attach mast sup-
port bracket to mounting holes halfway up back of
mast using four (4) 3/8"-16UNC x 2-3/4" long hex
head bolts, locknuts and flatwashers. (Place a flat-
washer under bolt head and nut and mount with nuts
on inside of frame).
12. Using a 4 ft. level, ensure mast is set to vertical
(plumb) on the base frame.
13. When mast is vertical (plumb), attach support
braces, (bolted to base), to the mast support
bracket, (bolted to mast), using 3/8"-16UNC x 2-3/4"
long hex head bolts, nuts and flatwashers. (Place a
flatwasher under bolt head and nut and mount with
nuts on inside of bracket).
14. After securing mast to base frame, using 4 ft. level
again check that mast is vertical (plumb) on base
frame.
Mast installation should now be complete.