Special is a trim name, not a model, so start with the code: the 1980 bike here is XS850SG. Yamaha's service manual for it is LIT-11616-01-79, which also covers the standard XS850 for the same year.
That pairing is the reason to check carefully. An XS850 and an XS850SG share most of their engineering but not all of it, and the book distinguishes the two where it counts. Reading the wrong column is an easy mistake to make on a forty-year-old triple.
The material is factory issue throughout: torque figures, wear and clearance limits, engine and chassis procedures in the intended order, wiring diagrams, and troubleshooting written as a sequence of tests. Match XS850SG on your frame plate and LIT-11616-01-79 on the manual before buying.
