Re: Must petcock be attached to tank?
also, having it on the tank means that (2 stroke) oil wont settle at the lowest part of the fuel system.
I had the petcock after the fuel filter. which meant that after about a month of not riding the bike, oil started to separate and collect in the fuel filter. this creates an uneven fuel mix in the fuel filter and this makes starting the engine very hard as there is too much oil in the fuel mix.