I PURCHASED A OLDER KDX 80 FOR MY SON. ITS A 1984. I REBUILT just about everything. new piston, pipe, clutches and steels, re gasketed the whole motor, painted the plastics, new set cover. basicly the whole bike. when i got it togeather, the vent on the carb keep leaking fuel. i figured it was a float or needle and seat problem but couldnt find replacement parts. i bought a oem brand carb and everything was great for a couple of weeks the the vents started leaking again. i took it apart but couldnt find anything that would cause it to leak. put it back togeather and it still leaked, so i called the company and they sent me another carb. i installed it and that was good for a couple months but now that one is leaking. is there somthing i am missing that could be causing these issues. i had put a in line filter between the tank and carb when i rebuilt the bike. the bowl of the carb looks clean as a whistle. what could be causing these to have a overflow problem?