1989 Yamaha VK540 Service and Repair Manual
Yamaha's LIT-12618-VK-50 is the service manual for the VK540, and the 1989 sled inside it is coded VK540EN.
Three model years share the volume, 1989 through 1991, with no other models mixed in. That makes it a straightforward book to use: what you read applies to your sled, subject only to the code differences noted between the three years.
The VK540 is a working machine and the manual treats it as one. Engine service is given with disassembly order, measurement points and wear limits. Carburetion and the oil system follow. The drive train chapter deals with the clutch, chaincase, track tension and alignment, and the suspension section covers both adjustment and repair. The electrical chapter includes wiring diagrams and the test values for coils, switches and charging components, so faults can be traced rather than guessed at.