JLG 19BD Service Manual - Manual (Page 56)

SECTION 2 - SERVICE PROCEDURES
2-34 – JLG Lift – 3121154
Mast Chains Adjustment - 15BD
The intention of this procedure is to assure equal load dis-
tribution between the individual chains of a mast section
chain set. Also to step each front mast section up approxi-
mately 1/4 in. (6.5mm) from the section behind it to allow
clearance for the individual mast section covers.
Adjust using the following procedure;
1. With mast retracted, step into the platform and
bounce your weight up and down a few times to be
certain platform is at the bottom of travel. Be certain
all chain sets are seated in their sheaves properly at
the top of each mast section.
2. Then with no load in the platform check the side pro-
file of the top of the mast for the amount of adjust-
ment necessary to obtain the 1/4 in. (6.5mm) step
for mast sections-3 and up. (See Figure 2-9.)
NOTE: Mast section-1 is fixed to the base and mast section-
2 is attached to the lift cylinder, these sections
require no adjustment.
3. Adjust one mast section at a time starting from the
back (section-3, section-4, etc.) of the mast and
work forward. (i.e.. if three is OK, then jump to four,
etc.)
4. To adjust, elevate the platform until the chain anchor
adjust nuts are accessible at the front and bottom of
each mast section.
NEVER WORK UNDER AN ELEVATED PLATFORM UNTIL PLAT-
FORM HAS BEEN SAFELY RESTRAINED FROM ANY MOVEMENT
BY BLOCKING OR OVERHEAD SLING.
5. Start with the mast section which needs adjustment
and loosen the bottom (jam) nut on each chain.
6. Tighten (to raise mast section), or loosen (to lower
mast section) the adjusting nut against the anchor
plate on each chain. Adjust the nut the amount
required to raise or lower the top of the mast section
to match the side profile shown in Figure 2-9. when
the mast is retracted. Be certain each chain pair is
adjusted to equal tension. (The threaded end of the
chain will need to be restrained while tightening the
adjust nut to keep the chain from twisting.)
7. Retract the mast all the way and check if the top of
the mast sections appear as shown in Figure 2-9.
8. Repeat steps (1) through (7) for remaining mast sec-
tions. ENSURE THAT ALL CHAIN PAIRS HAVE
EQUAL TENSION.
9. Once mast section adjustment is completed, apply
loctite #242 to the threads under the (jam) nuts that
were loosened. Then re-tighten the loosened (jam)
nuts until tight against the top (adjust) nut. Chain
should have slight tension but should not be taut.