03 and up have a diferent starter, starter clutch,and related parts. The gears connected to the starter were beefed up, and a back torque limiting device was added.
My 02 developed a problem with the starter clutch slipping, then catching, which would place a huge load on the gears connecting the starter to the starter clutch, and make a very loud pop. I changed the starter clutch with a new one, problem solved. IMHO, the 03 redesign is nice overkill, Suzuki just had a bad run of soft starter clutches. There is a sticky thread about this issue in the Busa problems section titled "A word to the wise".
Good hunting.
Karl