This service repair manual provides comprehensive information for the David Brown AD4 25 and CAD4 30 engines. These engines are known for their robust construction and reliable performance, making them suitable for a variety of demanding applications. This manual is designed to assist owners and technicians in understanding the intricacies of these power units, ensuring their continued operation and longevity. The scope of this manual covers essential maintenance procedures, detailed troubleshooting guides, and critical technical specifications necessary for effective upkeep and repair. By following the instructions and guidelines within this document, users can perform routine servicing, diagnose issues, and undertake necessary repairs with confidence, thereby maximizing the efficiency and lifespan of their David Brown engines.