1979 Yamaha XS400 Service and Repair Manual

The code to look for on a 1979 XS400 is XS400F, and the book Yamaha wrote for it carries part number LIT-11616-XS-42.

It is a broad manual by design. The factory used a single volume for model years 1976 through 1982, and the same text also serves the XS360 and the XS400 SPECIAL II. For anyone keeping one of these twins on the road, that means the specification tables show the whole family, so a part sourced from another year can be checked against the values for XS400F rather than guessed at.

Inside are the procedures a technician follows with the engine out or the forks on the bench: teardown order, measurement points, service limits, reassembly torque. Ignition and charging faults are approached through test values and wiring diagrams instead of parts swapping, and the troubleshooting sections start from the symptom an owner actually describes.