I have a problem with my 2006 WR450F. The idle speed varies quite a bit. Even when the bike is resting on the kick stand with no one around, the engine will speed up and slow down on its own. While riding, if you close the throttle you don't know whether you're going to slow down or if the high idle speed is going to keep pushing you. Yesterday, I went over a little jump and the engine stalled in mid-air. That was fun. The bike is completely stock -- no mods whatsoever. Any suggestions?