Did you look the bearing over in the big end? If the rollers aren’t discolored that color on the rod is from the heat treating.
the piston will score long before the crank gives up on straight gas
Huh? Look where the scarring is. It’s on the bottom. Bad bearings. Now what happened first is the million dollar question. Did the bearing fail first and cause the crank to overheat or did the lack of oil cause the crank to overheat and bearing to fail.The scaring in the crankcase maybe from the crank not being centered in the case, 660 cranks have to be centered, the bearings are not pressed to zero on crank, crank will rub and piston will not be lined up in cylinder.
See the heat line on the rod? If factory stihl rod don't have the bluing id replace the whole crank assembly. The metal properties have been changed and it is now unevenly hardened.View attachment 688831 View attachment 688832
Or maybe a better title would be "I found an MS 660 power head in a trash heap that needs new rotating assembly and bearings."
Piston looks unscathed but the rod was bound up on the crank. Straight gassed?
View attachment 688839 View attachment 688840
I have the rest of the big parts cleaned and drying. The saw is in great shape.
See the heat line on the rod? If factory stihl rod don't have the bluing id replace the whole crank assembly. The metal properties have been changed and it is now unevenly hardened.
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