This manual covers the Ducati Monster 400 and Monster 620 models from 2004 onward, offering comprehensive guidance for their service, repair, and maintenance. These iconic naked sportbikes, known for their distinctive trellis frame and potent L-Twin engines, represent a significant part of Ducati's heritage. The 400cc variant was designed to meet engine displacement restrictions in certain markets, while the 620cc model provided a more accessible entry into the renowned Monster lineup. Both models feature advanced engineering for their time, including Desmodromic valve actuation and fuel injection systems, contributing to their performance and rider engagement. This service repair workshop manual provides in-depth, A-Z coverage essential for owners, DIY enthusiasts, and professional mechanics. It details all diagnostic and repair procedures, from routine maintenance tasks like oil changes and chain adjustments to complete engine rebuilds and component restoration. Key areas covered include the engine, fuel and ignition systems, transmission, drivetrain, brakes, suspension, and electrical systems, complete with detailed torque specifications and comprehensive wiring diagrams. The manual is designed for ease of use, offering professional-level information to ensure the optimal performance and longevity of your Ducati Monster.