I bought a die ( or is that a tap?) and cleaned my threads. I used the petcocks off of a moped that have reserve, I was worried that they would be too small to feed a 850cc motor, but no issues there.
My only beef is that the one petcock hit the Cyl head on my Moto Guzzi and I need to use something like a screwdriver to turn it off when the motor is hot.