Zero Turn Mowers

Z254F only 4 hours on it.  Bought this to save me time but seems the handles are not alligned properly.  I see the nut / bolt on the base of the handles to adjust for reach but its not that.  When I push the left handle all the way forward and bring the right handle to the same even position it drives straight and cuts great.  Only thing is I can tell its not driving full speed.  The right handle will move about an inch farther forward and then the mower takes off and moves much quicker,  Issue being im not mowing in a circle so with the right handle being farther forward i drive with a slight left turn when moving fast.    Whats the easiest way to have this corrected without hauling it an hour back to the store.