This manual covers the Komatsu WA120-1LC Wheel Loader, a robust machine engineered for demanding operational environments. Designed with reliability and efficiency in mind, this model features the Komatsu S6D102E-1 diesel engine, a 4-cycle, water-cooled unit displacing 5.88 liters and producing 78.4 kW (105 HP) at 2200 rpm. Its advanced transmission, equipped with a lock-up torque converter and four forward and four reverse gears, ensures optimal power delivery for various tasks. With an operating weight of approximately 9,900 kg and a length of 6,685 mm with the bucket, the WA120-1LC is a versatile workhorse suited for construction, material handling, and other heavy-duty applications. The purpose of this Factory Service Repair Manual is to provide comprehensive guidance for the maintenance, repair, and technical understanding of the Komatsu WA120-1LC Wheel Loader. It details general information, structure and function, testing and adjusting procedures, disassembly and assembly, maintenance standards, and repair and replacement of parts. Specific sections cover the engine, power train, steering and suspension system, air system, work equipment, and electrical and electronic systems. This manual serves as an essential resource for owners, mechanics, and technicians to ensure the continued optimal performance and longevity of the equipment.