I got this toasted 461 awhile ago and I'm getting ready to rebuild it but I've run into a problem. Based off of Madsen's piston failure analysis chart and my personal knowledge of the saw's past life I'm guessing either dirt incursion or bearing failure caused the pictured marks on the piston, but I'm not sure which and was hoping one of you might know. If it is a bearing failure, how do I tell which one it is?