mine makes this noise as well. i've driven/ridden other vehicles with a similar noise, i'm quite sure it's the clutch.
i don't have any special knowledge about the Z - i've only owned mine for a few months - but if you look at an automotive-style clutch assembly you'll see lots of opportunity for noise when not engaged. probably it goes away when it warms up simply because when everything tightens up a bit when it gets warm.
my moto guzzi makes quite a racket when cold. i'm far more familiar with motorbikes which is why i'm saying things like 'automotive-style'.
i strongly suspect that every car does this, or would, had the engineers not spent the time to mask it. likely in a sports car like the Z the engineers were less concerned with mechanical noise.
also, i'm in burnaby so hi neighbour.
