I dont think this is the problem 81 kz550 ltd

I have a slow drip carb leak out of the first carb overflow tube. When i purchased the bike, this was the main problem along with it not starting. When i got the bike home i completely dissassembled the carbs cooked them in lemon juice and assembled and the bike started. But the number 1 carb still leaks. Others have told me it is dirt between the needle and seat and that is what my shop manual tells me but if it was leaking before i bought the bike, i did a through cleaning, and it still leaks, how could that one and only carb be leaking again??? This is just me procrastinating so i dont have to take the carbs off again really, im trying to sell it and i know that as soon as i take them off, someone is going to want to pick it up immediately and im going to hate myself

Consider swapping the float bowls between carbs and see if the leak moves with the float bowl.

Did you adjust the float levels per the factory service manual? How about new float needle and seats? It is also possible to have a float that leaks and therefore sinks causing fuel overflow/ flooding.

+1 to what motorhead said. I have the same carbs on my bike and the needles get a little scoring "ring" around them where they meet the seat and they begin to leak. I'd check Z1 enterprises, they might have just the needles, not the whole rebuild kit. That way you can minimize the hit to the billfold.

Sometimes an overflow tube is cracked.

One way to help diagnose a cracked overflow tube would be to swap with another float bowl, as suggested by kz750saskatoon, and see if the leak moves with the float bowl.

Good Fortune!

As mentioned a couple times above.....the bowls can leak due to issues with the overflow tubes. Remove the #1 bowl and carefully inspect it. You may be able to remove it while the carbs are on the bike if you have a 90 degree screwdriver.

I have several 550's with these carbs and I've had a few bowls that just leak

Float needle and seat are supposed to be paired together for life.
General rule is to re-new both at the same time.
In other words, don't re-new one without also re-newing the other.

When re-assembling the carbs incident cleaning, should be careful to fit the same needle with its same seat.

I believe new needles and seats are available from Z1E.

Sometimes polishing the seat orifice helps attain a better seal. A Q-tip soaked in carb cleaner and chucked in electric hand drill may be used to polish the seat orifice.

Good Fortune!

When you inspected the float needle, was there a wear ring around the tip? If so, it could just be worn too much to seal. Usually, though, if you run it for a few hundred miles the seat will re-lap the seal. Then it'll leak sometimes and sometimes it'll seal. From then you can just live with it (since i know money is tight and rebuild kits are $20 each).

I have one that leaks every once in awhile, but toward the middle of the season it leaks less and less. At the beginning of the season,especially the first day or two it leaks more. I know the needle and seat are really worn on that one, but I've been putting off replacing all four needle/seat on that bike.

The petcock must be working perfectly, though, or you risk losing a lot of gas. It's more important to have the petcock working right, so I'd spend the money on a rebuild kit for that if it's needed.