Common Carb Issue? Any solutions?

This is for the older flat head carbs 10-12 hp 1pc carb im pretty damn fimailar with them as i had my fingers in them for over 5years lol
recently on mine when i first got tractor i switched carb cause i all ready had one cleaned up with it on it runs great but it when done riding and it sits for a day or so it will flood with gas i've checked float and thats good i know the older carbs had the all metal valve and had a rubber ring like thing that it sat into to shut fuel off when bowl is full and the newer carbs had the valve with the rubber tip. Im sure when i checked mine was good but is it maby with age the rubber shrinks causeing it not to seal good?
i hate having to shut my fuel line shut off all the time. But dont want to flood my oil again. any one know where they sell cheap kits? ive been seeing them for $25 and up?

I do a lot of business with www.tewarehouse.com $9 shipping but they carry a lot of generic brands for cheaper.

by old 1 piece, do you mean the flojets?
the seat is prbly leaking. cheap fix.
make sure you put the rubber float seat in the right way (rings in)

some times this is caused by the emultion tube not seated properly.
just my experience, once they start leaking anything you do to fix it will make it worse.
shut off valves are cheaper than rebuilding the engine.
gas thins the oil and washes the oil off of the cylinder wearing out the rings quicker. This will also wear out the rod bearing quicker
( not really a bearing. but it will open up the journal clearances by eating out the aluminum rod)

The shut off valves are a pain in the ass at first, but you get trained over time and you will open/ close it with out even thinking about it

its the 1pc long carb with the needle having the rubber tip