This service repair manual covers the UniCarries K15, K21, and K25 internal combustion engines, designed for forklift powertrains. These engines are compatible with Nissan Forklift 1F1, 1F2, 1D1, and 1D2 models. The K Series engines are engineered for reliability and efficiency, providing robust performance for demanding industrial applications. This manual details the comprehensive engineering behind these units, ensuring optimal operation and longevity. This manual provides essential information for the maintenance and repair of the UniCarries K Series engines. It covers a wide range of topics including engine general information, tune-up procedures, engine mechanical aspects, lubrication and cooling systems, fuel systems, engine control, and electrical systems. By following the routine and preventive maintenance guidance, owners and technicians can prevent premature failures and unnecessary repairs, saving time and money. This easy-to-read guide is recommended for frequent use to ensure correct procedures are followed.