Originally Posted by maddog34

wrap your hand around the top of the headset, covering the upper and lower threaded parts' joint, as you test-rock it... you can then feel a tiny bit of slop that can't otherwise be felt as a "clunk".
whether it's a brake clunk, or headset clunk, or even WHEEL clunk, can then be determined.

sometimes all it takes is a 1/16 turn of the adjustment to get it perfect... or less.
minor issues with seal placement can cause a false drag on the headset, and the plastic seal won't clunk during a "bench test".. BUT your hand CAN feel the motion...