This manual covers the Komatsu PC300-6, PC300LC-6, PC350-6, and PC350LC-6 Hydraulic Excavators. These machines are engineered for robust performance and reliability in demanding operational environments. This documentation provides comprehensive details to ensure effective, economical, and safe machine operation and maintenance, facilitating optimal performance throughout the equipment's service life. The scope of this Service Repair Manual and Operation & Maintenance Manual is extensive, encompassing detailed information on maintenance, assembly, disassembly, and servicing. It includes procedures for testing, adjusting, and troubleshooting, alongside essential technical specifications and safety guidelines. This manual is designed to assist owners, mechanics, and technicians in understanding, maintaining, and repairing these hydraulic excavators, ensuring their continued efficient and safe operation.