Left side carb over flowing after shutting bike off.

Please help! My 1982 kz440 started leaking a small amount of fuel out of the left side overflow tube when I shut it off. It only happens when the bike is off and not while it's running. I have the floats adjusted to spec. No cracks in overflow tube. I'm lost. 

Check your float valve to see if it closes and seals properly.

Sounds like the petcock isn't shutting off fuel like it should when the engine is off.  Also, the fuel level is too high in the leaking carb, most likely from a sticking/dirty float valve.  Checking float level isn't good enough, you need to check fuel level in the bowl.

As others have stated, it's most likely a sticking float valve.
Modern fuel gum or crud can often cause it.
Before you go ripping the carbs apart;
Check petcock filter and ensure it's clean.
Be sure you have good fresh fuel in the tank.
Consider fitting a fuel filter in the fuel line, depending on the room you have under there, but get a quality one.
Should be quite an easy job.
For a while when you finish riding, turn the fuel off and let it run a short time, then shut it off. This will reduce fuel in the system and minimize the overflow.
If you have a vacuum pet cock, you may be limited to one system's worth of fuel that will flow out.
You may well find this problem will clear in time and fitting a filter may stop it from happening again (or until it's gum, then they'll need to come off for a clean)
Also park as upright as possible and side stand lean may not help.
Good luck and hope it passes.