If you manually move the right break over further away from the breaking point doesn't move the left brake out of the way? If it does in the PTO engagement needs to be adjusted.
While I truly appreciate your attempts to help me, PTO adjustment is not the answer. I don't know what is, but it's not that. When the PTO engages, the big spring at the end of the PTO cable pulls the left blade brake arm to move the brake away from the pulley, which also disengages the right brake by way of item #32 brake control rod. When the PTO is disengaged that big spring is relaxed, allowing the right brake to be pulled toward the pulley by its spring. The problem is that there's nothing to pull the left brake toward its pulley. Again I ask, what does the item #22 spring attach to? I can't identify that spring anywhere on my deck, which leads me to believe that it's missing and that may be what's wrong.

