I replaced the stock belt on my zx50 with a Malossi kevlar. I got some fuzz like that after the first week or so. I'm assuming it was caused by the belt seating into the taper of the pulleys. It was not anything like yours though! I cleaned it out, I could blow most of mine out, and it has been fine since. Seems to perform better also, especially under acceleration. I would have to give it a thumbs up!