First I need someone to explain how the pto engages the belts. My 169 seemed to almost stop the blades in a little deeper grass. Today I see the pto is what's not turning. Now today when I went back a few hour later the pto will not engage at all. Not sure where to start. I hope it something simple. I just got done getting all new belts on the deck, figured out and rebuild the Mule drive. Now the pto quit. Please help me understand how this device works.