Hi, i have an older exmark metro 5 speed (around 2005, i think).  I''m having an issue where the right side drive sheave is slipping/spinning on hills.  I've tried replacing the drive belts on both sides but the problem persists. i would like to replace the smaller sheave that is attached to the transmission (part number  	103-6511) and i can't get it off.  I have removed the set screw but the sheave won't budge.  Any help would be greatly appreciated.    Thanks.