Need some help with number plates

I've got some sticky stuff from the numbers on my 125, I've tried alcohol, windex, just rubbing it, and nothing is working really well. Also there is some black spots or specs on the front one. Any idea how to get rid of this? Thanks!

(Here is a pic of the black spots. They are in the middle of the 0 and around where the numbers were)
7A2008A5-0EBE-498A-BF2A-D6AFEE23F385-22584-00000594C197532B_zpsa4f1572b.jpg
 
Top