Original documentation produced by Yamaha. The service manual is highly recommended as a reference. In this PDF the text has been OCRed (so you can search it) but the photographs aren’t great.
Scans of the original Yamaha parts books.
Various sales brochures and publicity material produced by Yamaha to promote the bikes. Thanks again to XS Paul for providing the original artworks.
Technical Service Bulletins
Yamaha Technical Service Information bulletins were sent to official Yamaha dealers only. They contained details of problems, modifications and various warranty issues related to Yamaha bikes. These are UK-specific and contain lots of interesting period information. Thanks to XS750 Paul for making them available.