YB40000207 Excavator Hydraulic Main Pump Valve Plate for Hitachi ZX350-3

The part number is YB40000207, which is the original hydraulic main pump valve plate specially designed by Hitachi for the ZX350-3 medium-sized hydraulic excavator. This component is the core valve body for controlling oil circuit distribution and pressure regulation in the hydraulic main pump. Its universal model usually covers ZX350-3 and other models with the same series and main pump configuration, and may also be applicable to 5B series excavators with similar tonnage such as ZX330-5B and ZX370-5B.

This product is a square valve plate made of high-strength cast iron precision machining. The main body is in the shape of a thick plate, with several key oil passage holes distributed on the surface: two transverse long elliptical holes are the inlet and outlet of the main pump high-pressure/low-pressure oil chamber; The circular hole in the middle is mostly a process hole or a return oil channel; The longitudinal large elliptical hole is usually the working chamber or pilot pressure oil passage of the variable control piston. The valve plate is internally cast with complex intersecting oil channels, connecting various hole positions to achieve the distribution, unloading, and directional control of high-pressure oil. Its working surface (the surface in contact with the port plate) needs to achieve extremely high flatness and smoothness.

Inspection and handling: After disassembly, if rust is found as shown in your picture, professional handling must be carried out: 1 Cleaning: Use specialized cleaning agents and ultrasonic cleaning machines to remove oil sludge. 2. Rust removal: Remove rust from non precision mating surfaces, but it is strictly prohibited to damage the edges of oil passage holes and critical sealing surfaces. 3. Measurement: Use a knife edge ruler and a feeler gauge to check the flatness of the valve plate (usually required to be ≤ 0.01mm). If it exceeds the tolerance, it needs to be ground and repaired by a professional manufacturer.