This manual covers the UniCarries Engine K15, K21, and K25 series, specifically designed for Nissan Forklift models 1F1, 1F2, 1D1, and 1D2. These engines are engineered for robust performance and reliability in demanding industrial environments. The associated Nissan Forklift Internal Combustion 1F1 and 1F2 Series Service Repair Manual provides comprehensive information for these specific forklift models, ensuring efficient operation and longevity. The purpose of this collection is to serve as a definitive guide for the maintenance, repair, and technical understanding of the covered engines and forklift series. It includes detailed procedures, diagnostic information, technical specifications, and safety guidelines essential for owners, mechanics, and technicians. By utilizing the information contained within, users can effectively maintain peak operational efficiency and ensure the safe and proper functioning of their equipment.