Yamaha YFM660RN Service Manual page 58

PERIODIC MAINTENANCE/LUBRICATION INTERVALS
NOTE:
Recommended brake fluid: DOT 4
Brake fluid replacement:
1.When disassembling the master cylinder or caliper cylinder, replace the brake fluid.
Normally check the brake fluid level and add fluid as required.
2.On the inner parts of the master cylinder and caliper cylinder, replace the oil seals every two
years.
3.Replace the brake hoses every four years, or if cracked or damaged.
WARNING
Indicates a potential hazard that could result in serious injury or death.
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CHK
ADJ