My buddy came riding with us on a left over 05WR450 he just picked up. It had 6 miles on it at the start of the day and 26 miles at the end of the day. For the entire day it behaved like a two-stroke with a lean pilot jet. When ever you let off the throttle, the engine wouldn't return to idle speed right away. You had to wait a good 30 seconds for it to drop down to a reasonable idle rpm. I'd guess when you let off the throttle, the engine tried to hold a 2500rpm for 30 seconds before dropping down. This bike had only 6 miles on it and is totally bone stock without a scratch on it. Any advice is appreciated!