This manual covers the Komatsu PC100-6 and PC120-6 excavators, part of the -6 Series. These diesel-powered machines are engineered for robust performance and reliability in various construction and excavation applications. The PC100-6 features a 4.20 L engine producing 72 kW (97 HP), with an operating weight of approximately 9,900 kg. The larger PC120-6 is equipped with a 5.57 L engine delivering 78 kW (105 HP) and has an operating weight of around 11,800 kg. Both models utilize a hydrostatic transmission, offering variable gear control for efficient operation. Their durable construction and advanced hydraulic systems, including impressive digging depths and reach capabilities, make them versatile tools for demanding job sites. The purpose of this Service and Repair Manual is to provide comprehensive guidance for the maintenance and repair of the Komatsu PC100-6 and PC120-6 excavators. It details essential information, including engine specifications, transmission operation, and detailed technical data on dimensions and hydraulic capacities. The manual outlines critical service intervals for engine and hydraulic oil changes, along with specific oil capacities for each model. This resource is designed to assist owners, technicians, and mechanics in ensuring the optimal performance, longevity, and safe operation of these machines through accurate procedures and technical insights.