Ducati Monster 796 Workshop Manual page 577

Cylinder/piston assemblies
Check that the walls of the cylinder bore are perfectly smooth. Measure the cylinder bore diameter (D) at three different
heights and in two directions offset by 90°, thereby determining the assembly clearance, taper, and ovality (see specified
values in Section 3 - 1.1, Cylinder/Piston).
In the event of damage or excessive wear the barrel must be renewed as it has a silicon carbide coating (which provides
the cylinder walls with excellent anti-friction and anti-wear properties) and therefore cannot be rebored.
The cylinders are marked by a letter (punched into the specific surface on the cylinder side) showing the size class to
which they belong.
Always match cylinders with pistons from the same size class.
Overhaul of the piston