I just had the top of a piston come off in a Wisconsin AEN engine. No damage other than the top of the piston. Looks like it cracked/separated around the bottom oil ring. I can find a piston on fleece-bay, NOS but it list them as DB-209-5 S10, S20, etc. The parts manual calls it a DB-209-5. What is the S10 or 20, etc?
Engine ran great until this, was rebuilt before I received it 8 yrs back, have ran probably 40-50 hours a year on a log splitter.