Originally Posted by
dabac
What you refer to as the "body" is commonly known as the "head tube".
If it was me, I'd pull that apart to see if there are two crown races on top of each other.
That would explain the gap nicely.
This^^^.
I would pull the fork out and make sure
1- The crown race is fully seated.
2- There is only one crown race.
3- The crown race, bearing, and headset cup (the part in the frame) all fit together well. Being a used bike/fork, there is always a chance that someone put in a new fork with the wrong crown race for the headset.