8050658 Excavator Hydraulic Main Pump Parts Piston Assy for Hitachi ZX200-5A

Part number 8050658 is a genuine piston assembly produced by Hitachi Construction Machinery Co., Ltd. in Japan, which is the core moving component inside the hydraulic main pump. Its universal model mainly covers the Hitachi ZX200-5A model, and may also be applicable to 20-22 ton excavators on the same platform, such as ZX200-5G and ZX210-5A, which use the same series of main pumps (such as HPV series). As the core repair package component of the original pump, its ball head diameter, plunger outer diameter, and length are precisely matched with the pump cylinder bore. It is strictly prohibited to use pistons that are not original or do not match the size, in order to avoid internal leakage, insufficient pressure, or abnormal wear of the main pump.

This product is the piston and slide shoe assembly of a hydraulic main pump inclined disc plunger pump. The main body is a precision cylindrical body made of high-strength alloy steel, with one end being a high-precision spherical head, which is riveted or press fitted with a bronze or composite material slide shoe to form a piston slide shoe assembly; The other end is flat. The spherical head contacts the main pump's inclined plate, converting the rotational motion of the inclined plate into the linear reciprocating motion of the piston inside the cylinder. The outer diameter of the plunger is usually strictly divided into size groups (such as grouping tolerances within 0.002mm), and the surface is subjected to ultra precision grinding and special treatment to form a stable oil film lubrication in the cylinder bore, achieving high-pressure sealing. The typical working pressure can reach over 35MPa, and the material and heat treatment process ensure high compressive strength and wear resistance.

Installation specifications (requiring extremely high cleanliness): 1 Cleaning: Before installation, all related parts such as the piston assembly, pump casing, and cylinder body must be thoroughly cleaned in ultra clean hydraulic oil or specialized cleaning agents. 2. Inspection: Measure the outer diameter of the piston and the corresponding inner diameter of the cylinder bore using an air force gauge or precision micrometer to ensure that the fit clearance meets the maintenance manual standards (usually 0.01-0.03mm). 3. Lubrication and installation: Apply a sufficient amount of clean hydraulic oil on the surface of the piston and cylinder bore, and then manually insert the piston smoothly and unobstructed into the cylinder bore. It is strictly prohibited to strike.