They regulate the voltage that comes from your stator and lighting coil to make it low enough so it will not blow your light bulbs and melt your hand/thumb warmers right off. I let my buddy's FIII 600Triple warm up for like 20mins with the hand and thumb warmers on high I sat on in to take it from a drive and the voltage reg was screwed it melted my gloves to the handle bars..lol.
Grant.
Grant.
