As others have said there is no specific torque, it depends on too many other factors.when i got it the center bolt in the headstem was loose.
Thanks
Doesn't really matter if the centre bolt on the cap of the headset is loose - it's only used for preloading and its redundant once the stem is on and bolted up.
This can also happen if the gap between the top of the the steerer and the top of the stem (or spacer if you've got any above the stem) is too small or too large.but can't seem to get a happy medium