6.1 General description
The hydraulic system mainly consists of main pump, control valve, high & low
pressure oil pipes and joints. The main pump is a gear type and installed on the side of
the transmission. As the engine runs, the main pump is driven to draw up oil from the
tank and send it to the control valve. The control valve, provided with a relief valve to
keep the circuit pressure within the specified one, controls the cylinders by changing
over the oil passages inside the valve body with the spools.
6.2 Main pump
The main pump consists primarily of a drive gear, driven gear and pump body
which contain the two gears and other components. The drive gear is in mesh with the
driven gear.
6.3 Control valve (See Fig.6.1)
The control valve is a sectional type consisting of the inlet section, plunger section
and outlet section which are assembled with three bolts.
At the inlet section there is a cartridge type relief valve to set the oil pressure in the
circuit. The steering relief valve is used for adjusting the oil pressure in the steering oil
circuit. Twist them clockwise, raise the oil pressure, on the contrary, reduce the oil
pressure. The plunger section controls the hydraulic cylinders by changing over the flow
of oil from the relief valve with plungers. The tilt cylinder plunger section is equipped
with a tilt lock valve. Oil returned from the cylinders is returned to the tank through the
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