This workshop service repair manual covers the Caterpillar K15, K21, and K25 gasoline engines, designed for use in forklift trucks. These engines are built with Caterpillar's renowned engineering quality and reliability, offering robust performance for various material handling applications. The manual details engine displacements of 1.5 liters for the K15, 2.1 liters for the K21, and 2.5 liters for the K25, all utilizing gasoline fuel. These engines are integral to forklift models ranging from the GP15N and GPE15N, supporting capacities of 1500 kg, up to the GP35N and GPE35N, capable of handling 3500 kg. The purpose of this comprehensive manual is to provide essential information for the maintenance, repair, and servicing of these Caterpillar engines. It includes detailed procedures for scheduled maintenance, fluid capacities, and parts identification, ensuring optimal performance and longevity. Owners, mechanics, and technicians will find valuable guidance on troubleshooting, technical specifications, and safety protocols. This English-language resource, identified by manual code 99789-85110, is an indispensable tool for keeping your Caterpillar-powered forklift equipment operating efficiently and reliably.