Hitachi NV 75AG Technical Data And Service Manual page 30

(b) Reassembly
Disassembly procedures should be followed in the reverse order. Note the following points:
Be extremely careful to prevent the entry of foreign particles into the control valve section.
Thoroughly apply grease to the O-Ring (I.D 1.8) [60] on Plunger (A) [59], O-Rings (I.D 11) [56], (S-18) [54]
and (S-4) [48] on Valve Piston (B) [57], and the shaft of Plunger (A) [59] as shown in Fig. 17.
As shown in Fig. 17, install Valve Bushing (A) [61] so that the roll pin groove in Valve Bushing (A) [61] will be
aligned with the roll pin hole in the Body [18]. First, insert a roll pin puller (3 mm (0.118") dia.) into the roll pin
hole. Then, upon confirming that the puller passes through the hole, drive in the Roll Pin D3 x 28 [38].
If an attempt is made to drive the roll pin with force when the roll pin groove in Valve Bushing (A) [61] is not
aligned with the roll pin hole in the Body [18], it will damage the periphery of Valve Bushing (A) [61] and
prevent disassembly or reassembly.
Body [18]
Roll pin
groove
After assembling, check that Plunger (A) [59] moves smoothly.
Roll pin hole
Roll Pin D3 x 28 [38]
Valve Bushing (A) [61]
Apply grease to the stem.
Valve Bushing (A) [61]
Fig. 17
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Coat the O-ring
groove's shaft
with grease.
Plunger (A) [59]