Ducati Diavel Carbon Owner's Manual page 172

Rear brake pedal
7
Loosen counter nut (7).
Turn pedal stroke adjusting screw (6) until pedal is in
the desired position.
Tighten the counter nut (7).
6
Operate the pedal by hand to check that there is
0.12÷0.24 in (3÷6 mm) of free play before the brake
bites.
If not, adjust the length of the master cylinder
pushrod as follows.
Slacken the counter nut (10) on the pushrod.
Screw the pushrod (8) into the front fork (9) to
increase the freeplay, or screw it out to reduce it.
Tighten the counter nut (10) and recheck the pedal
freeplay.
10 9
8
Fig 116
170