Leaking fuel from carb - '77 kz400 deluxe

Hi all, the latest of what seems like a never ending string of problems on my '77 KZ400 Deluxe has been that my left carb is leaking a significant amount of fuel through the overflow tubes. The engine still runs fine and idles normally while this is happening (although I shut it off as soon as I noticed the leak). I have also noticed significant fouling on the spark plugs.

Is this more than likely a float/needle issue?
I've never done any carb work. If someone has a good step by step walkthrough of how to troubleshoot this, that would be awesome

Thanks!

It sounds like it's probably the valve needle. That's what stops the fuel from flowing into the carb bowls when they fill up.