8071391 Original Excavator Hydraulic Pump Piston Assy for ZX110

The original hydraulic pump piston assembly of Hitachi excavator, with part number 8071391 (also commonly known as plunger kit or HPK055), is the core maintenance component of the hydraulic main pump. This assembly is mainly suitable for Hitachi ZX120 and other ZX series small and medium-sized excavators. As a genuine original accessory, its precise size and material ensure a perfect match with the internal mechanism of the hydraulic pump. It is a key spare part for pump body overhaul, restoring pump volumetric efficiency and working pressure, and can effectively ensure the stability and reliability of the hydraulic system after maintenance.
 

The piston assembly 8071391 is the core moving component of the inclined disc axial piston variable displacement pump, typically consisting of a set of precision paired pistons, sliding shoes, return discs, and other parts. Its core function is to perform reciprocating motion within the pump cylinder (pump chamber), suction and discharge hydraulic oil through volume changes, thereby converting mechanical energy into hydraulic energy. The parts are made of high-strength alloy steel and have undergone precision machining and heat treatment, resulting in extremely high dimensional accuracy, surface hardness, and wear resistance.
 

The piston assembly is an internal precision component of the hydraulic pump, and its lifespan is directly related to the maintenance level of the entire hydraulic system. The primary maintenance key is to maintain absolute cleanliness of the hydraulic oil, and it is necessary to regularly replace compliant hydraulic oil and filter elements to prevent pollutants from entering the pump body and causing abnormal wear of the plunger and cylinder body. During operation, it is necessary to monitor whether the system pressure and flow rate are stable. If there is slow, weak or abnormal noise from the pump body, the performance of the pump should be checked.