This workshop service manual provides comprehensive guidance for Twin Cylinder OHV engines, specifically the 405777 and 445777 series. These robust engines, featuring displacements of 656cc and 724cc, are engineered for reliability and performance across a wide range of applications. This manual covers all essential systems, including ignition, fuel, lubrication, and electrical components, ensuring optimal operation and longevity for your equipment. This English-language manual is designed to assist owners and technicians in maintaining and repairing their engines. It includes detailed step-by-step instructions for disassembly and reassembly, repair and inspection procedures for various components, and specifications for tightening torques and special service tools. With detailed illustrations, pictures, and diagrams, this manual serves as an invaluable resource for troubleshooting, routine maintenance, and complex repairs, ensuring your engine remains in peak condition.