2005 WR450F On the first ride, the engine is slow to "run down". i.e. if I'm reving and I pull in the clutch and close the throttle, it stays rev'd and just slowly.. over 5+ seconds works - works its way back down to idle. If I lug the engine a little with the rear brake or whatever, the idle goes right back down like it should. I keep turning the idle down and it gets better. After 10 or 20 minutes of riding the problem goes away (and I maybe have to turn the idle back up because I've turned it too low). Any ideas?