If the disc has worn past the service limit, replace it.
Measuring Area [B]
Brake Disc Thickness Standard:
Front 5.3 
5.7 mm (0.21
0.22 in.)
Rear 4.8 
5.2 mm (0.19
0.20 in.)
Service Limit:
Front 5.0 mm (0.20 in.)
Rear 4.5 mm (0.18 in.)
Brake Disc Installation
Brake Disc Warp InspectionBrake Line Bleeding
The brake fluid has a very low compression coefficient so
that almost all the movement of the brake lever or pedal
is transmitted directly to the caliper for braking action. Air,
however, is easily compressed. When air enters the brake
lines, brake lever or pedal movement will be partially used
...
Rear Frame Front Removal
Remove:
Rear Frame Rear (see Rear Frame Rear Removal)
Rear Fender Front (see Rear Fender Front Removal)
Rear Footpeg Bracket Bolts [A]
Rear Footpeg Bracket [B]
Rear Frame Front Bolts [C]
Left Rear Frame Front [D]
Remove:
Rear Footpeg Bracket Bolts [A]
Rear Footpeg Bracke ...
Check 3-5: Warning Indicator Light (Red LED) (Oil Pressure Warning)
Inspection
Connect the leads in the same circuit as Check 3-2.
Connect the terminal [10] to the battery (–) terminal.
Check that the oil pressure warning symbol [A] and the
warning indicator light (Red LED) [B] go on.
If the indicator light does not go on, replace the meter unit.
...