Casting Flaw?
The point I guess I am trying to make is that the hole in the piston crown is right below the Decomp valve--dead center below. If anything, the fact that the owner and operator rarely used the decomp valve when starting makes this an even greater mystery.
BTW, do you or anyone else know what metallic alloy that Stihl is using to make these pistons?
I doubt that because the same owner has another MS 650 running flawlessly with the same number of hours. He also told me today that he rarely uses the Decomp valve. He has very strong arms and can drop start the saw even when cold.Could it be as simple as a casting flaw in the piston, resulting in an area that was slightly thinner than its surroundings? Might not ever show on a normal saw, but showed on this high-hour saw?
The point I guess I am trying to make is that the hole in the piston crown is right below the Decomp valve--dead center below. If anything, the fact that the owner and operator rarely used the decomp valve when starting makes this an even greater mystery.
BTW, do you or anyone else know what metallic alloy that Stihl is using to make these pistons?