[Rich in Tucson]

Try to "stake" it first - place seat on anvil and tap needle with ball pein hammer face (don't hit hard, or soft, just let hammer fall on to it by relaxing your wrist), hit it once square (or twice if you reflexively held back!).

I have lapped with toothpaste as a lapping medium or with valve grinding compound by turning the needle on the seat by hand, but I find that staking never fails. I always stake new needle and seats (even NOS) and bench test carburetors in various ways and it is obvious when an old in service valve needs staking...