Want to pep up wizard rider but still function

[jzebrook]

I have a 6 speed wizard riding mower 42" cut ( model: ayp7147a39) with a 14hp twin B&S (model: 400707) what I'm looking to do is speed this thing up but still function. More or less a 10-15mph top speed which from what I seen is still capabile of cutting. Reason is on the longer straight parts of my lawn it takes forever and even at full throttle the motor is working hard but not enough speed for me. I know a motor this size should be capiable to do this speed a lower rpms. Which would put. Less strain overall on the motor. I'm assuming it because of gearing and pulleys which would. Make since because of what these are designed to do but I have normal grass no high or thick stuff so I don't need nearly the tourqe this thing has. Now I don't think the governer would do what I want because it has the power at lower rpms but maybe not I'm more trying to find out where to find and what kind of pullleys do I need? Are all pulleys generic so I can measure the size and buy by belt and mounting specs? Should I go smaller in the front (big pulley? ) and larger in the back (small?) Lol really any info even basic on the gearing of lawn tractors or this one specificly would be great thanks in advance!!