The Komatsu PC300-6, PC300LC-6, PC350-6, and PC350LC-6 series excavators represent robust construction equipment engineered for demanding tasks. These machines, powered by the Komatsu SAA6D107E-1 Diesel Engine, offer reliable performance with a net power output of 177 kW (237 HP) at 2000 rpm. Their design emphasizes durability and efficiency, featuring a hydrostatic, electronically controlled transmission and a water-cooled engine. With operating weights ranging from 30,400 kg for the PC300-6 to 34,600 kg for the PC350-6, these excavators are suited for a variety of heavy-duty applications in construction and earthmoving. This Shop Manual provides comprehensive guidance for the maintenance and repair of the Komatsu PC300-6, PC300LC-6, PC350-6, and PC350LC-6 excavators. It covers essential information including detailed technical specifications, lubrication requirements, and recommended service intervals for engine oil, filters, and hydraulic systems. The manual also includes procedures for troubleshooting and repair, ensuring that owners, mechanics, and technicians can effectively maintain the operational integrity and longevity of their equipment. This 747-page document is an indispensable resource for understanding and servicing these powerful machines.