My bike's always had a bit of a rattle from presumeably the head re: valves and things, but just recently it's gotten a fair bit more constant and louder and above 9000rpm (redline is 11k) the engine's suddenly losing most of it's power (feels like valve bounce) quite suddenly like the valves aren't tracking properly or something. Maybe it's something else. Any ideas on what might most likely be the cause and repair costs of such a problem? I'm hoping it's just an alignment thing or the timing chain/belt/whatever a GS500 uses is on it's last legs. Unless anyone knows of more serious problems common to these motors.