carburetor sweating fuel ??

This is the carburetor bowl off my KE100. I filled it with gas to near the top of the shorter overflow tube. The pic was taken about 30 minutes after filling. The fuel level is lower than origionaly filled. It is not leaking around or through the over flow tubes, but seams to be seeping through the pot metal, as if it were sweating. Also, if I dry the top lip of the bowl, it is wet again in a few miniutes. Capillary action?

Are you sure it's not evaporating and condensing onto the top surface. If it's warm fuel doesn't take long to evaporate. Bit of clingfilm once filled will stop evaporation. 
Try dusting the outside of the bowl with talcum powder. You'll soon see if the bowl is porous or leaking and where from. 

I tried the talcom powder trick. It appears fuel vapor is condensing on the top of the bowl and working its way down the sides. It seems odd, fuel and carb both spent the night on my work bench in the garage.
The problem I was looking into was a slow drip of gas on garage floor (about 1 drop every 10 seconds). It will stop in a few hours once the fuel has drained out of the fuel line, provided I remember to turn the petcock off.
The float needle in this carburetor is all metal, has no rubber tip. Are these known to leak?
 

If there is a visible ring worn in the needle cone then it would be best to replace both the needle and seat as a matched pair. 
If the cone has no visible wear marks then clean the seat face with toothpaste and a cotton bud to ensure there's no foreign matter build up preventing clean needle seating.
When in good nick the all metal needles seal well.