nelska,
I've got a KFL clone from FT, and had a couple problems with it leaking. First, the inside of the top cap is different than the real one, and the o-ring is finicky about seating onto the chimney. I found out the hard way what happens when this isn't seated properly. The other problem was the air channel wasn't drilled out cleanly and there was debris in where the it met the center channel. It was still passing air, but it was like a tight draw, so I was pulling hard and sucking too much juice and flooded the deck. Once I found the debris and cleaned it out, the leaking problems disappeared.
-C