Ducati MONSTER Owner's Manual page 26

To change the preload of the spring inside each fork leg,
turn the adjusting nut (2) with a 22-mm/0.87-in. hexagon
wrench.
Preload setting range (A) is from 25 to 10 mm/0.99 to
0.39 in.
Factory setting is 18 mm/0.7 in.
Important
Adjust both fork legs to same settings.
E
26
1
3
2
A
fig. 18.1
fig. 18.2