I have tried to follow ParkTool adjustment tips for the B-screw of the rear derailleur (other company's tips are similar) , but I fail to detect the condition "the upper pulley rubs the largest cog".
I have completely unscrew (removed) the B-screw, but even shifting from the second largest to the largest cog shows no interference.
I can, of course, make the upper pulley rub the cog, if I manually rotate the rear derailleur towards the cog. The problem is that the adjustment of the B-screw cannot reproduce this symptom.
Is that normal, or should I worry my rear derailleur was mal-installed?
For your information, the instructions I have followed for the B-screw adjustment are the following:
EDIT: I think it may be a chain length problem, as if the tension was reduced (longer chain), the upper pulley might touch the cog depending on B-screw adjustments. I will check the equations to calculate the chain length and compare against the existing chain.