Oster Regency kitchen center question

Question

 I got a deal on a lightly used Oster Regency kitchen center. I had it apart and back together, but now I want to use it and I cannot get the mixer part to tilt back so I can remove the beaters and bowl in order to attach the meat grinder attachment. I'm using the lever system on the back of the mixer unit but it seems to be not working because the beaters are on, but I can't get them off.....see what I mean? I do not have the manual so I can't double check how it is supposed to work.Can you help me?