The Hitachi ZAXIS 650LC-3 and 670LCH-3 represent the third generation of ZAXIS hydraulic excavators, designed for robust performance and reliability in demanding construction and earthmoving applications. These machines are engineered with advanced hydraulic systems and powerful diesel engines to deliver exceptional digging force and operational efficiency. Their substantial operating weight, ranging from approximately 63,500 to 67,700 kg, underscores their capability for heavy-duty tasks, while the hydrostatic transmission ensures precise control and smooth power delivery. This service manual provides comprehensive guidance for the maintenance, repair, and technical understanding of the Hitachi ZAXIS 650LC-3 and 670LCH-3 excavators. It covers essential areas including detailed maintenance procedures, troubleshooting common issues, and critical technical specifications. The information contained within is intended to assist owners, operators, and service technicians in ensuring the longevity, optimal performance, and safe operation of these powerful machines through proper upkeep and informed repair practices.