Was out today riding for a ahort while and ran full speed in 4th gear on the street. At about half throttle in 4th gear I hear a unfamiliar sound coming from the engine area. Sounded like a loose washer rattling on a shaft? I have noticed this sound at the track last month in 3rd also. I've opened it up full throttle couple of times in 4th and pushed other gears to red line so I know the engine has been ridden a little. My 05, 450 has about 25 hours on it and I have not yet checked the valve clearances on it yet. Does this sound like a valve issue? I'm a little cautious about checking the valves since this is my first time doing this kind of procedure. Ya know; "don't fix it if it aint broke" Thanks!