The Thunderbolt S3 and S3T, produced for the 1999 through 2002 model years, represent a distinct era in performance motorcycle engineering. These motorcycles are characterized by their air-cooled, 45-degree V-twin engines, displacing 1203 cc, and a design philosophy that integrated sportbike performance with the robust torque of a V-twin. Notable innovations, such as the frame serving as an oil reservoir, contributed to their agile handling and unique aesthetic. The S3T variant further enhanced aerodynamics and rider comfort with the addition of a fairing. These machines were engineered for enthusiasts seeking a blend of power, precise handling, and distinctive American performance. This comprehensive workshop service manual provides essential information for the maintenance, repair, and troubleshooting of the Thunderbolt S3 and S3T models from 1999 to 2002. It covers all major systems, including the engine, fuel, ignition, lubrication, exhaust, electrical, transmission, chassis, brakes, wheels, tires, and bodywork. Detailed procedures for routine maintenance, diagnostic analysis, component disassembly and assembly, and performance tuning are thoroughly explained. This manual is an indispensable resource for owners, mechanics, and technicians aiming to preserve the integrity and performance of their motorcycles, offering step-by-step guidance for a wide range of service needs.