Leaking carb has me stumped!! Help!

Fired up my KZ1000 project and seems to run well but the carb on #2 cylinder refuses to quit leaking out of the overflow on the bowl. I've tried two different needles and seats, pulled the carbs probably eight times to check floats, change needles, seats and it still acts like the bowl is flooding. Odd thing is it drips from the bowl just a little then sort of shoots a stream of gas out, then drips, then shoots gas again. I've installed new rubber tipped needles, steel tipped needles, several seats and they all act the same way. The carb has the nitrile floats so I don't think the float is the issue. Any ideas? By the way thee carbs are vm26 mikunis 120 main jets with 17.5 pilots.

Fuel overflowing through the carb overflows must get into the carbs from the fuel tank. Normally this fuel comes from the tank through the float valves into the bowls. However, there is this one exception-

If you do NOT have a vacuum operated petcock, skip to CARB OVERFLOW POSSIBILITIES below. IF you have a vacuum operated petcock it is possible that fuel is coming into the #2 carb through the vacuum line from the petcock rather than through the float valve. So if you have a vacuum operated petcock that is attached to the #2 carb I would try this: Disconnect the vacuum line from the carbs and hold it over a catch can. Regardless of the position of the petcock handle, no fuel should flow through the vacuum line. If it does, rebuild or replace the petcock. If no fuel flows through the vacuum line then see below.

CARB OVERFLOW POSSIBILITIES

Remember - NO SMOKING or other activities that could ignite the fuel while working on carbs!

The float valve is not sealing. This may be (and probably is) just a matter of some minor dirt in the float valve and is very simple to remedy and can be done with the carbs still on the bike. Turn off fuel; drain carb by loosening big brass screw near bottom; and remove the 4 little screws on the bottom of the carb bowl. This will enable you to remove the carb bowl. You will then see the float. If you carefully remove the float you will see a stubby little needle that mates with a brass orifice; together, these two pieces are the float valve. Assuming there is no obvious damage to the needle or seat, use a Q-tip and some carb cleaner to clean the seat of the orifice and the needle. Be careful not to bend the tang that is attached to the float. This tang is the piece that the bottom of the float valve needle rests upon, and it determines the fuel level in the bowl, so bending it will change the fuel level. With the float valve cleaned it should no longer leak. To prevent a re-occurrence a quality inline fuel filter should be installed between the fuel tank and carbs. If there was damage the needle and seat should be replaced as a set; they are available.

The brass overflow tube inside the carb bowl is damaged. When you remove the carb bowl you will see a brass tube attached inside and rising toward the top of the bowl. This is the overflow tube and it leads directly to the overflow nipple on the bottom of the carb. Normally, the fuel level within the bowl rises somewhat close to the top of this tube. If the tube becomes cracked or separates from the bottom of the carb bowl fuel will flow through it and out through the overflow hose. Checking the condition of the tube is very easy after you have removed the carb bowl from the carb. Simply hold the bowl level and fill it up near the top of the tube with water or alcohol and see if it leaks. A slight crack in the brass overflow tube can be difficult to find. You can connect a rubber tube to the overflow nipple, fill the bowl with water, put finger over the open end of the brass overflow tube and blow in the rubber end and look for bubbles. If it does the best remedy is to replace it although some folks have found creative ways to repair them.

The fuel level is set too high. This condition occurs when someone has bent the float tang as mentioned above. This condition can be checked using what is referred to as the "clear tube test." The test involves attaching one end of a clear piece of flexible tubing to the carb drain hole and holding the other end of the tube above the bowl/carb joint. When the fuel is turned on it should rise in the tube to a level 2.5 - 4.5 mm below the bowl/carb joint. If the fuel rises higher than that level it may run into the cylinders or over the upper end of the brass overflow inside the carb bowl (mentioned above) in which case it will run out the overflow hose. This condition is corrected by removing the float and gently bending the tang to raise the float valve needle position. Doing this may take several tries before achieving the desired fuel level.

Correcting each of these three conditions involves removing the carb bowl. This task can be made easier if a short screwdriver bit is used, and depending on which carb you are fixing a mirror may help you locate the screws on the bottom of the carb bowl. Also, it is not a bad idea to have a new carb bowl gasket available in case the old gasket is damaged while removing the carb bowl. Ed

Disconnect the fuel line & route it to a container using a long section of tubing.
Then see if fuel leaks into the container. Manual fuel valve set to OFF. Vacuum petcock set to ON.

PS: my 81 650 leaked as you describe whenever the vac petcock diaphragm was bad.

Problem solved, removed bowl again and checked the brass overflow tube on your advice and found a hairline crack in it extending the length of the tube, replaced the bowl with a spare and I'm good to go. Thanks for the replies!!