Have a listen to the attached file, it usually does this when cold, or when left for a few days, i have just changed the oil and filter (and flushed) with 0W20. Still the same
Only occurs when the engine idles high briefly, on start up, though i have started it in icy cold mornings in 3 inches of snow, it didn't rev high, hence no rattle, which i found odd.
I can possibly get a better vid of the rattle sound if required, please help.
rattle.mp4