i am at work, can't listen to the sound.. will do that once i am home...

If you can not clearly pinpoint the sound to an external source, the last thing left is internal location in the engine... once the chain start slapping around, the aluminum casing of the engine will break, as these engines are designed to crumble in case of an impact, as a safety feature in an accident... ask me how I know... well, don't ask me, it is still a sore subject!!! lol...

I sure hope I am wrong about your case...