I had a similar thing one day on my XT600 after parking up at my mates house his wife said there was fuel dripping, theres a discharge tube from carb above the float chamber somewhere, if the needle jet gets stuck it
discharges the surplus fuel. On the XT there's also a tube from the bottom
of the float chamber where there's a small screw set just above it, the problem in my case was some dirt had fouled the needle jet, luckily giving the float chamber a couple of sharp taps with the plastic end of a screwdriver then unscrewing the small screw flushed the dirt out, remember to catch the fuel in a clean container to see any resultant foreign matter.
