I took mine off and cleaned it and put in a new O-ring.
It leaked just the same. It is a bad design, take it apart, you will see.
Better to cut an old piece of fuel line with a plugged end and stick that on the petcock outlet when the tank is off.
'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.