No wiggles or wobbles here, try these tips-
The adjustment is just spring or damping related, probably preload. It has only a small effect on steering geometry which is your likely problem. Not enough trail in the steering, causing "tank slappers"
First check the headset for loose, tight, pitted or worn bearings- most common cause. Is the steering action smooth?
Then the front wheel:- check for rim runout and bearing play, run max air pressure on a slick tyre to eliminate a possible cause, a low pressure knobby on pavement could cause cause a wobble.
Get the seat lower and the bars higher, this will improve your center of gravity and put more weight on the rear end.
If the above checks don't eliminate the problem then its time to start measuring the frame alignment and frontend geometry.
I think you don't have enough trail, (blue line) but its hard to tell by the pic.
More trail is slower steering, less is faster.
Bicycle Steering Geometry
Bicycle and motorcycle geometry - Wikipedia, the free encyclopedia