1989 Yamaha SRV Service and Repair Manual
A 1989 SRV wears the code SR540N, and the manual Yamaha wrote for it is LIT-12618-SR-07.
One volume handled the model from 1984 to 1991. For an owner that means the year-to-year differences are documented side by side rather than split between books, which helps when a machine has been kept running with parts from whatever was available.
The procedures are written for measurement. Engine sections give torque sequences and wear limits, fuel and ignition work is set out with adjustment figures, and the electrical chapter carries wiring diagrams you can actually trace a circuit through. Clutch, track, suspension and steering each have their own coverage, as does the periodic maintenance schedule.
Confirm SR540N on the sled before you buy, then read the tables by that code and the 1989 specifications come out unambiguous.