Re:'82 KZ1000 fuel pouring out of the air filter

Problem #1-First and foremost the carb float may be moving freely but the needle that the float is attached to sometimes can get debris between the needle and the seat, thus not shutting off the flow of fuel.  Most carb floats have a mechanical connection.  This would be a small wire clip that is clipped onto the top of the needle and the ends of the clip surround the lever on the float.  This clip mechanically  pulls the needle off the seat when the float bowl drops down.  Occasionally, these clips have been misplaced or not properly installed.  This can sometimes be the problem.  In your application the needle and seat are replaceable.  If your carbs still have rubber tipped needles you may consider the all brass needle and seat.  Theses are less sensitive to the new fuel additives. At no time should there be fuel running out of the air filter.  This an indication that your carb float bowl overflow tubes are clogged.  These must be clear and have proper length hose attached to where they allow the fuel if any to drain below any hot surfaces on the motorcyle; ie: mufflers, tailpipe, etc.  As far as fuel flowing from the carb vents while sitting on its side stand at idle, this could be due to excessive angle of heel.  You may have to adjust your kick stand to stand the bike more upright.  Personally, I would change out all of the needles and seats in all four carbs as per the manufacturer's settings.