This manual covers the UniCarries Engine K15, K21, and K25 series, specifically designed for Nissan Forklift models 1F1, 1F2, 1D1, and 1D2. It also includes comprehensive information for the Nissan Forklift Internal Combustion 1D1 and 1D2 series, along with details for the QD32 E engine. These forklifts are engineered for robust performance in demanding industrial environments, offering reliability and efficiency for a wide range of material handling applications. The focus on quality construction and dependable operation ensures these machines meet the rigorous standards expected in commercial and warehouse settings. The purpose of this manual is to provide detailed guidance for the maintenance, repair, and technical understanding of the specified Nissan Forklift models and their associated engines. It encompasses essential maintenance procedures, diagnostic troubleshooting steps, comprehensive technical specifications, and critical safety guidelines. Owners, service technicians, and mechanics will find this resource invaluable for ensuring the optimal performance, longevity, and safe operation of their equipment through accurate and thorough information.