If your 1100I is like my 2004 EVT, the speedo has a "cup" with 2 allen screws to hold the cup on. If so...
The screw goes into a nut that is rubber mounted to the speedo. If the rubber has failed, the screw just turns.
To remove the cup, you need a very small 6mm?? wrench to hold the nut on the back. I use what I think are called ignition wrenches. You reach in through the speedo cable opening and hold the nut.
Even with good rubber, I still use a wrench to hold the nut when I need to take the cover off.
If you need a pic, I can take a few latter today.