first ,there should be no slack BETWEEN the pulley and the shaft( the shaft will wiggle a small amount) , if you have movement between the pulley and shaft you should remove the pulley and check that the teeth on the pulley and the main shaft are square ,and not worn to a point. If they show wear you have a problem ,if not the nut holding the pulley should be torqued to 100-130Nm or 73-94ft/lbs before bending over one side of the washer that keeps the nut from backing off.
 second, the key should never be turned on for any length of time without the bike running, If you used the kill switch to stop the bike and then turned the switch back on,  the key being on would send power to the ignition module which can overheat and destroy it  ,you could unplug the module and try a new fuse to check if that 's your (expensive to replace ) problem. If the fuse blows your problem is a dead short ,and elsewhere.(and you got lucky). In the future if you need to check anything electrical, with the key on, unplug the module to protect it from damage.

   It's behind the left side cover , the module is the small black box ,and the plug is a six wire, and directly  inserted into it .