Mast To Base Frame Installation - JLG 25AM Service And Maintenance Manual

2.11 MAST TO BASE FRAME INSTALLATION

1. Using an overhead crane or suitable lifting device capa-
ble of supporting the weight of base frame, attach a sling
strap or chain to the front crossmember 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 con-
tainer 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 cylinder mounting
channel tab using a 5/16 in. x 5/8 in. 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 cross-
member.
7. Attach mast to base using four (4) 3/8 in. x 1 in. long hex
head bolts, flatwashers, and nuts. (place a flatwasher
under bolt head, mount with nuts on inside of frame). Apply
Medium Strength Threadlocking Compound to bolt
threads before final tightening of nuts.
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SECTION 2 - SERVICE PROCEDURES
8. 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.
9. Carefully set machine in an upright position on its base
frame wheels.
10. Locate the mast support bracket. Attach mast support
bracket to mounting holes halfway up back of mast using
four (4) 3/8 in. x 2-3/4 in. long hex head bolts, locknuts
and flatwashers. (Place a flatwasher under bolt head and
nut and mount with nuts on inside of frame).
11. Using a 4 ft. level, ensure mast is set to vertical (plumb)
on the base frame.
12. When mast is vertical (plumb), attach mast support
braces, (bolted to base and mast support bracket) using 3/
8 in. x 1 in. long hex head bolts and lock nuts.
13. 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.
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