I have never liked the tread pattern on the Dunlop D207 or D208 tires.
When those tires start to wear a bit they develop a side to side vibration.
I had a Buell XB9R that came stock with D207.
I always had to keep one hand on the bars to keep them from developing a high frequency wiggle in the bars. If I didn't, it would start to develop a head shake.
I thought the tire or wheel was out of balance, or the steering head bearings were worn.
However I tried replacing the tires with Pirelli Diablos and the problem went away.
I would try replacing the D208 with a tire using a different tread pattern.