JLG 4017 Operator Manual - Manual (Page 90)

Section 5 - Emergency Procedures
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Lowering Boom
6. Locate the valve (5) on the lift cylinder. Measure the height of the small bolt.
Remove the bolt. Remove the jam nut from the bolt. Reinstall the bolt until it
bottoms out.
7. Retrieve the handle located in the operator’s cab toolbox. Install the handle on
the lift/lower valve section of the main control valve in the engine compartment
(see “Valve Layout” on page 5-2). Using the handle slowly activate the valve to
lower the boom.
8. Once the boom is lowered, reinstall the jam nut onto the bolt and reinstall into
valve to previously measured height.
9. After machine is repaired and prior to first use, activate the joystick to ensure
the holding valves are working properly.
WARNING
TIP OVER HAZARD. Load check valves need checked for proper operation by
qualified service technician anytime after opening. Improperly adjusted load
check valves could cause tip over resulting in death or serious injury.