The petcock can leak two ways, one is to the outside and the other is through the petcock.
If you take one apart you will see it is built like a bung. There is an o-ring that keeps it from leaking to the outside. That can be replaced to stop that problem.
I can't see how to fix the through leakage but someone might know more.
'02 KTM 640 Adventure-lowered
"On the road there are no special cases."
Cormack McCarthy-The Crossing
The faster it goes the faster it breaks.
And high performance=high maintenance.