Originally Posted by
milchad
From Park Tool website:
B-Screw Adjustment
After setting the L-screw, check the "B-screw" for an adequate setting. The B-screw controls the derailleur body angle, hence the name, B-screw. Shift to the innermost rear cog, which is the largest cog. View the upper pulley relative to the largest cog. If the pulley is rubbing against this cog, tighten the B-screw to increase upper pivot spring tension, which pulls the pulley back and away from the cog. If there is a large gap between the upper pulley and cog, loosen the screw. To find a good setting, loosen the B-screw until the upper pulley begins to rub, then tighten the screw to get clearance.
Oops, I forgot to mention that I had set up the B-screw properly as well. The pulley is not contacting the cog.
Speaking of the pulleys, though---does it matter which pulley goes on the bottom of the cage and which goes on top? I've noticed that the two pulley wheels are different (different bearing types).