RS125 Rev counter flips

[Mikail]

Hi,

I have an aprilia rs125 11kw restricted version (but the cdi bridge is cut)

The rev counter bounces up and down when I throttle, and indicates 0 rpm when i don't throttle.

I'm convinced that the needle of the rev counter isn't perfectly fitted in it's spot. So i want to open de rev counter but I don't know how. I've already unscrewed three bolts en removed a protective foam of the dashboard. But I can't remove the "glass" of the revcounter. Can someone help me out?

Greets

P.S. The cables should be fine so no problem there