I just pulled my 400 apart yesterday. Its sounded horable. The big end bearing is fine, the piston looks good (being changed anyways) the valves look straight. The timing chain is stretched bad (its an 01 with no maintance ever) but I am worried that the auto decompressor is bad. The bike had little compression while kicking, which made me think I had a bent valve. It ran fine but sounded bad and smoked. The decommpressor cam just flops back and forth on the cam. I am going to press the deal apart and make sure the little spring is there. Is that what the pin and spring in the head are for as well? I have a manual but it doesn't discuss how the actuator works with the one way clutch. Anyone? Is most of my noise from the spent cam chain?