Hmm...it sure sounds like you did it properly. You replaced the float needle you said? And is just one carb overflowing or both?
My KZ550 had the ol' honda cb900/1000 Custom problem...which might plague you as well. Make sure that your brass overflow tube doesn't have a hairline crack in it. I polished the float valves, got new needles , changed float heights and it STILL leaked gas. I found the crack, and soldered it up, no more leak! Might be your issue too.
... Make sure that your brass overflow tube doesn't have a hairline crack in it. ... I found the crack, and soldered it up, no more leak! Might be your issue too.
NO to JB weld.VERY simple. Make sure you have flux, even the stuff used on copper pipe in your house (if you have ever had to fix plumbing) will work. Get it good and hot with the solder gun before you put any solder on it. Then quickly get solder on the gun and go back to it (keep as much heat as possible on it) and it should flow really easily to the whole length of the crack. Good luck, it's worked every time for me, but that's a pretty large crack, make sure you get enough solder on it!