Recently got an shimano ultegra rd-6500
I'm finding that the pulleys are noisey, doesn't seem to be an adjustment issue, shifting is just fine. But the lower pulley (farthest from hub) makes ... kind of a rapid slapping noise as each link of the chain engages/disengages from it.
It's annoying as heck when riding.

Any advice on reducing noise?
Dissasembly and regreasing of the pulley bearing doesn't seem to be any help, chain is all oiled too...

As an experiment, I temporarially swapped the pulley with older ones from an Alivio derailer and the noise goes away, but thats not a working solution since the width is different... tho it does bring up an odd point, the rd-6500 has 11tooth pulleys and the old quiet one has only 10. I wonder if that is a factor...

Thanks