This manual covers the Komatsu 125-1 Series Engine, including variants such as the 6D125-1, S6D125, and SA6D125. This diesel engine features a 6-cylinder inline configuration with a displacement of 7.5 liters. Designed for robust performance, it typically operates within a power range of 150-250 horsepower and utilizes a direct injection fuel system and water cooling. The engineering quality and reliability of the Komatsu 125-1 Series are well-established, making it a dependable component across various industrial and heavy-duty applications. This comprehensive Repair Workshop Manual / Service Manual provides essential information for the maintenance and repair of the Komatsu 125-1 Series Engine. It details critical procedures, technical specifications, and maintenance schedules, including guidance on lubrication with diesel engine oil, oil capacity, filter types, and coolant requirements. The manual also outlines service intervals for oil changes and air filter replacement. This resource is invaluable for owners, mechanics, and technicians seeking to ensure optimal performance, longevity, and proper functioning of their Komatsu engines.