4330909 Original Excavator Piston Pin for EX120-5

The original piston pin part number 4330909 is a key connecting component in the Hitachi EX120-5 series excavator engine. It is mainly compatible with EX-5 series medium-sized excavators such as EX120-5, EX100-5, EX130-5, and may also be compatible with similar models of Hitachi excavators such as EX120-3C and EX120. The piston pin is installed between the piston pin seat and the connecting rod small head, used to transmit the gas explosion pressure borne by the piston to the connecting rod, driving the crankshaft to rotate. When placing an order, the engine model (such as Isuzu 4LE2, etc.) and serial number must be provided to ensure that its outer diameter, length, and inner hole shape fully match the original engine assembly.

This product belongs to the fully floating hollow piston pin, usually made of high-quality low-carbon alloy steel (such as 20Cr, 15CrMo), and treated with carburizing and quenching. The surface hardness can reach HRC58-62, and the core maintains the toughness of HRC30-35 to achieve mechanical properties of external hardness and internal toughness. Its structure is a thick walled hollow cylinder, and the inner hole may be in the shape of two truncated cones to reduce weight and approach the design of an equal strength beam. As an original component, its dimensional accuracy, roundness, and surface smoothness are strictly matched with Hitachi's original engine, ensuring sufficient rigidity, strength, and wear resistance under high temperature (200-300 ℃), high pressure (instantaneous over 100MPa), and poor lubrication conditions, avoiding abnormal wear, noise, and even fracture caused by precision or material issues of secondary components.

It is recommended to check the engine oil quality and pressure every 1000 working hours, and monitor for any abnormal knocking sounds (caused by excessive clearance between the piston pin and the pin seat). Disassembly and measurement: During major repairs, it is necessary to measure the outer diameter of the piston pin and the inner diameter of the pin hole, and calculate the fit clearance (usually 0.002-0.005 mm); Check the surface for scratches, peeling, or excessive wear. Installation specifications: Before installation, the piston pin needs to be frozen or the piston needs to be heated for easy installation; Ensure that the retaining ring is installed in place to prevent axial movement. Lubrication and replacement: The piston pin relies on splash lubrication to ensure the cleanliness of the engine oil; If the gap exceeds the tolerance or there are longitudinal scratches or discoloration (overheating) on the surface, it must be replaced immediately. Replacement suggestion: The piston pin belongs to the core motion pair of the engine. It is recommended to replace it together with the piston and connecting rod liner, and use original parts to ensure size matching and heat treatment performance consistency, avoiding early wear or cylinder pulling caused by improper fitting.