I was out riding this weekend, and noticed that my Sportster is making an audible "whirring" or "whining" noise while riding. I only notice it at decel, but I probably just cant hear it at speed. It doesn't make the noise while sitting still and running, and doesn't start right away after taking off from a light. It's constant with the clutch in or out, and it stops abruptly once I slow to about 10 mph. I have read a number of treads on a number of websites, and heard everything from "no big deal" to "you're about to grenade your transmission" and I wonder if anyone has insight. I believe I read somewhere that Evos have shitty failure-prone main shaft bearings, but I can't seem to find it now. Oh, and its a 5-speed, with 25k on the clock (a little over 20 of that in the last 2 years) and hasn't had anything done to the tranny, or the case apart. Anyone?