Zero Turns

Just got the Z254 zero turn and this thing worked great for the first hour. My mower now has 1.1 hrs on the meter. The issue I am having is when I pull the PTO up to engage the blades the mower bogs down like its about to die. If I sit there for a min you can hear the blades start to speed up but then soon as I hit new grass you can hear the blades sputter out and the mower just about dies. What could be the problem and how can I get to a solution.