If a master cylinder or piston shows any damage, replace them.

If a cup is worn, damaged softened (rotted), or swollen, the piston assembly should be replaced to renew the cups.
If fluid leakage is noted at the brake lever, the piston assembly should be replaced to renew the cups.
If they are damaged, replace them.
If the springs are damaged, replace them.
If the relief port becomes plugged, the brake pads will drag on the disc. Blow the ports clean with compressed air.
Front Master Cylinder [I] Rear Master Cylinder [J]

Rear Master Cylinder Installation
Brake DiscTie-Rod and Rocker Arm Bearing Removal
Remove:
Tie-Rod (see Tie-Rod Removal)
Rocker Arms (see Rocker Arm Removal)
Swingarm (see Swingarm Removal)
Sleeves [A]
Oil Seals [B]
Remove the needle bearings [C], using the bearing remover
head and bearing remover shaft.
Special Tools - Bearing Remover Head,
15 ×
17: ...
Engine No. ZXT00JE003023
1. Heat Insulation Rubber Plate
2. For Air Switching Valve Hoses (Place the air switching valve above the
rubber plate.)
3. For Stick Coils
4. For Throttle Body Assy Holder #2 and #3
5. For Water Temperature Sensor
6. Insert the tab into the slot.
7. For Throttle Body Assy Holder #4
8. ...
Mode-switching
Depress the S-KTRC button on the left handlebar switch
to change the mode. The mode can be changed only when
the throttle grip is closed completely.
The S-KTRC OFF can be selected only when the motorcycle
is at a stop. Changing to mode 1 from S-KTRC OFF
is possible while riding.
NOTE
...