AMG, i just took apart a 21 with over 2 gallons in it for some major cleaning and havent noticed anything like this. Ive taken apart several engines in the past and havent seen this before. by the way, if something like dirt or shavings exists in your crankcase it doesnt have to neccessarly enter the with the fuel flow to your piston conmustion area but just hang around below your piston and thus you dont see scaring on the piston/sleve. just brainstorming. interesting indeed.