Sorry to bump my boring thread again, but I want to since I just saw that the answer came in:
I asked what's unique about the death rattle of an Echo. I gathered that it's not unlike the death rattle of any other small saw engine, from what you dudes posted here (thanks). I gather that maybe some Echos die at a higher rate than some other saws, because they are shipped with overly lean carb settings (mine were anyway).
But THEN, the international expert on the uniqueness of this rattle finally weighed in, and had nothing to say about it, other than that Echos suck, and that I and others are greenhorn morons. It turns out that the latter isn't true. Also, the expert's report constitutes a pattern for me that clearly evidences something special: southern hemisphere air must be so dense that a saw can't be adjusted to survive it. Surely these adjustments were attempted.
So, case closed for me. If the champion of breaking these saws can't characterize their widely-mentioned swan song, I figure it's nothing special. I've proved to myself at least that the saws can be used hard without dying. Maybe my cutting technique is wrong? I like to run cutters pretty high over rakers, the saw turns medium RPMs and makes long chips, as a result H jet is usually richer for me than it would need to be to hit factory-nominal max RPM, which I don't care about.