Yamaha XZ550RJ 1982 Owner's Manual page 173

Inspecting the brake fluid level
Insufficient brake fluid may allow air to enter
the brake system, possibly causing the brakes
to become ineffective.
Before riding, check the brake fluid level and
replenish when necessary, and observe these
precautions:
- 161 -
1. Use only the designated quality brake
fluid; otherwise, the rubber seals may
deteriorate, causing leakage and poor
brake performance.
Recommended brake fluid: DOT # 3
2. Refill with the same type of brake fluid;
mixing fluids may result in a harmful
chemical reaction and lead to poor per-
formance.