I had one where I had to install 3 seats before it stopped leaking. Otherwise, you could have had dirt in the tank that prevented the needle from seating. Maybe you still do.

Carbs shouldn't need to be rebuilt after two years, unless the proper storage techniques weren't used. And even at that, there's a couple of things I always do after not using a unit for a prolonged period of time.

Sounds like the 2nd cleaning solved your problem.

You didn't mention the make and model of your motor, does it have a fuel filter ?
thanks,