Technically you can adjust the jetting of the Victa.
Its the first rule in the basic principal of a Carburettor, the fuel height effects everything.
So techincally by adjusting the float height in a victa (either by swapping needles or turning the primer face) you can adjust the jetting.
I would say that if your fuel economy has worsened since you did something on the machine you need to go over what you did again.
