2 leaking carburetors

I just cleaned and put a rebuild kit in the carbs of my 82 KZ550. The two left carbs are leaking and I've taken them apart and set/checked the float levels multiple times but they still keep leaking gas out of the bowl overflows. I've tried knocking on the carburetors, as other people had suggested, to loosen them but it had no effect. They also seem to leak from the air filters as well. I installed a K&N pod filter setup and put in a dynojet 98 size jet in the carbs. For the brief moment I run it, the bike runs fantastic. Has the best throttle response of any bike I've ever owned. But for some reason those two left carbs keep leaking, and not just a drip here, a drip there. Pouring straight out of the overflow shortly after I turn the fuel tap to Prime. Any ideas or suggestions?

What method did you use to set the float height? The clear tube is the ONLY way to set that height. Just search the site and you can find a ton of info on the technique. You tube also has videos on this, and if you look at the most recent posts on my thread "kz900 semi restoration" I detailed the process for another member. Long story short...you either have a bad needle valve, improperly set float heights, or floats that don't float. My guess is the middle, and a clear tube is the only way to tell for sure. Or a clear bowl...why wont somebody make those...

eddiekilowatt wrote: ... keep leaking gas out of the bowl overflows. ... also seem to leak from the air filters as well.....

Would sniff-test and examine the oil for possible fuel contamination.

Would suspect that at least one carb overflow circuit is malfunctioning (probably blocked) as gasoline is rising up past height of the the overflow tube and into the carb bore.

Blockage in the overflow circuit might be in the brass tube or perhaps the overflow hose is kinked or collapsed.

Good Fortune!

Regarding the carb overflow -

Assuming you did not install the floats upside-down -
Fuel coming out of the overflow hose (the little hose on the bottom of the carb) is the common symptom of the 3 possible problems described below. 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

I used to do this every six months: take the brass seats and needles out and polish them. The needle can go in a low speed hand drill and polish the tapered part with 600 paper on a popsicle stick until shiny smooth. They sometimes get rusty or pitted. If you can't get it smooth, you need a new needle.

I also would wrap the brass seat threads with tape and put it in the drill and polish the inside where the needle mates with a Q tip and chrome polish until dead shiny.

Once done, you will get a perfect seal.

BUT: as stated above, you must do a clear tube measurement and set the fuel levels after.

Thank you for all your suggestions, I hope to have some time to tackle again tonight and (hopefully) have good news to respond with after.

A friend of mine took a look and realized the floats were bent inward and the inside of them was bumping against the jet towers. He tweaked them back and problem solved. This bike runs so nicely. Best throttle response of any bike I've ever owned. Picked it up for $460 titled and sorely needing a carb clean to run but not really knowing what it would need after that. So far plugs, oil/filter, a carb kit, K&N pod filters, and a dynojet 98 size jet kit and it sounds wonderful. Riding to work tomorrow morning for the first time in 4 years. :woohoo: