A friend of me has a wr400f year 2000. Last time he used bike it started to rev with the throttle closed and very strange noise came from engine. When he got back home and checked the compression it was poor.... After removal of cylinder head he performed a leak test on the valves and they where leaking... At first no visual damage to valve, cylinder or piston. After inpection of carburator he saw that parts of "valve,neddle" were missing and what was left of it had cracks. (see yamahapart.com, exploded wiew of carb, part nr 11) The parts had been sucked into engine and damaged valve and seat. He has asked "yamaha people" about this issue but they had never heard of this before. Anyone here who has exp the same?