Tecumseh carbs are prone to flooding (or leaking) because they are gravity fed. If the float valve seat or float goes bad, they'll start leaking gas on your garage floor. This can also be caused by a gummed up carb, but look carefully at the float and valve seats when you disassemble the carb. Newer "float bowl" type B&S carbs are using the same Viton valve seat, so this can be applicable there, too. A bad seat can also cause fuel starvation. ONE of the signs of a bad seat is the needle action being spongy or sticky.
Here's an unusually clean Tecumseh carb stripped and ready for a float
valve seat replace. The Tecumseh needle and seat part number
is 631021. But before you do this, check the float. If the
float rattles when shook, it means that the float has sunk and will need
to be replaced or repaired. When I say "sunk" I mean that it has
sprung a leak and is letting gas (or water) inside it, which makes it float
less or not at all.
The Viton seat is down set at the bottom of the fuel inlet. I
use a small wood screw to pull them out.
Here's the new seat ready to be pushed in by "an appropriately sized
drift" (in this case a bolt). The side with the ring should face
into the gas flow. Usually they're white, but this aftermarket seat
Push it down and seat it.
Rule of thumb says the float should be level after assembly.