Even though you cleaned the needles and seats, they could still leak. It doesn't take much to lose the seal and when it's gone, it's gone. Black and wet is fuel, so it's a spark, compression or fuel problem. You didn't say, but you might want to run a compression test. If you run out of options get a couple carb kits. Or just the needles and seats if possible.
Check carb synchronization too.
