If the handlebar vibrates you may have slack or even that you have the steering tube outside the guide of the lower ball bearing. Between the tube and the ball bearing you have a plastic adapter system that could be dislodged from the place.
The solution is to disassemble the upper butterfly, the handlebar of the tube, the aluminum washers of altitude and to be able to remove the steering tube with the wheel to fix again the plastic adapter that brings back to the ball bearing, install again and make pressure, adjust everything to millimeter and put everything back in reverse order, the secret is the tightening of the handlebar, those 2 screws are what prevent the direction from moving from its place and take upper or lower clearance.
The ball bearing is a closed or semi closed system. The balls are not loose or lose. Without fear.
If you do not tighten those 2 screws of the handlebar firmly to the steering tube, the problem will arise again.
When you tighten the handlebar you can not have vertical clearance in the steering tube.
That plastic between ball bearing and well placed prevents the steering tube and the ball bearing from colliding mechanically .
