You can measure the thickness of the working surface of the disk using a caliper without removing the wheel from the motorcycle.
Replacing the brake disc with the wheel removed (see «Front wheel - removal and installation»).
1. With a 6 mm hex wrench, unscrew the six disc mounting bolts.
Before installing the disc, treat all mounting bolts with an anaerobic thread locker. The tightening torque of the bolts is 8-10 Nm.