These are the gold standard for technical accuracy, containing every torque spec and wiring diagram. They are widely available as PDFs on enthusiast forums and document-sharing sites:
: Specifically for the 300cc variants.
For those just looking for basic service data without a full 300-page manual: Vespa Scooter Service & Repair Manuals Vespa Gts Repair Manual
: Newer versions (2019+) require specific HPE manuals due to engine changes. These are the gold standard for technical accuracy,
: Covers the 250cc fuel-injected models, including detailed maintenance rules and system overhauls. Vespa Gts Repair Manual
Finding a reliable depends on whether you want the official "Workshop Service Station Manual" used by dealers or a more user-friendly DIY guide. 1. Official Piaggio Workshop Manuals