Our 97 500 has 7500 miles on it and the valves were only adjusted once and that was 7 years ago. Are you sure the rattling is not from recoil, the rewind and bendix drive rattle all the time.
600 miles is about 60 hr for my type of riding.
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2001 Yellow SP 500
No ECM
No Plastic roller cage
5.25 gal tank.
