Dont give up on it yet it's gotta be something simple(it will be when you find it )especially since it happened suddenly. More thoughts: put the old aircleaner assy back on & see what happens. maybe the underside of the lid on the new one is too close to the vents but I wouldn't think it'd cause that kind of richness. I'm wondering if one of the wells in the phenolic body sprang a(slight) leak and when you had the top off neither of the floats were waterlogged? I would take the whole carb off & go over it w a fine tooth comb. You'll have a good laugh when you spot it.