JLG Lull 1044C-54 II Series Service Manual page 289

Cleaning and Inspection, Frame Tilt Control Valve
31200079
(Ref. Fig. 7-4) The following procedures are for the disassembly, cleaning,
and assembly of the frame tilt control valve. Follow the guidelines for
cleanliness as stated in Section 3 of this manual.
1. Thoroughly clean all parts, except for the lever assembly, in clean
solvent and dry with compressed air. Do not immerse the lever
assembly in solvent. Solvent can become trapped in the assembly and
will be difficult to remove.
2. Pay particular attention to the porting in the valve body. Flush valve
body with clean solvent and use compressed air to dry.
3. Inspect each spool for scratches and damage. Scoring on the spool
may also indicate damage to the ported guides . If damage is evident,
replace with new parts. Check fit of spools in ported guides. The
spools must fit snugly with no sticking. A stuck spool can cause
unintentional operation of a hydraulic circuit. Excessive play or sticking
means that the spool and its ported guide must be replaced.
4. Check surface of each plunger and guide for wear and damage. Check
fit of plunger in guide to make sure no sticking occurs. Like the spools,
a stuck plunger can cause unintentional operation of a hydraulic circuit.
5. Inspect each spool cavity in the valve body for scratches.
6. Check condition of lever assembly, cam, pivot pin, springs, and flange .
Replace as necessary.
7. Replace O-rings and seals as necessary. Lubricate O-rings and seals
with clean hydraulic oil before installing them.
Frame Tilt and Oscillation
7-7