KZ650 SR Mikuni Carb#1 flooding

So as the title says, Carb #1 is puking fuel out of the overflow line. I pulled the carbs and to my dismay, looks like the previous owner was a gorilla and stripped the crap out of the float bowl screws. amazingly enough, i got them out (not sure what i'm gonna do to get it back on), but i want to avoid re-tuning them. They were re-jetted but i dont know what size jets. I fear the ethanol in the fuel is probably causing varnish to build up. i've given it a good soaking with carb cleaner, but i'm sure thats not likely to be enough. Any suggestions on what i can do to try to clear it up without a full tear down?

Regarding the carb overflow -

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 of 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

Thanks for the informative response, Ed! The bowl itself is in good shape and the overflow valve appears to be fine. The float needle does seem to be the likely culprit, though i'll pull the float this morning and clean it up to be sure.

Couple of questions: 1) i'm noticing most carb bowls should have a rubber gasket, mine do not... they dont leak or anything, so is this a problem? (perhaps thats why the previous owner stripped the heads off the screws putting the bowls on?) 2) the hoses that connect the float bowls to each other, what do they do? just maintain consistent levels between all 4 carbs?

No eBay APP ID and/or Cert ID defined in Kunena configurationThe carb bowls should have paper gaskets (not rubber) that look like the one in the eBay listing below.

Please post a picture of the carb bowl hoses you mentioned. There should be no hoses connecting the carb bowls to each other. The bottom of the carb bowls should have hoses that run down toward the ground between the swingarm and the back of the engine. These are overflow tubes and it is very important that they be unobstructed, otherwise is fuel overflows it can run into the engine. They should be tyhe only hoses attached to the carb bowls. If yours were not running out to open air, I strongly suggest you snif your engine oil to see if it has been contaminated with fuel. If it has, change it and the filter before running the engine and after fixing the carb overflow problem. Ed

Ok, so to clarify a couple things, looks like the hoses i mentioned are attached to the float bowls but dont actually go *into* them. Also, looks like the paper gasket is intact, i just didnt realize it was there See picture below

I assume these are part of some EGR thing?

I don't know for sure because my carbs don't have the accelerator pump, but I suspect those hoses connect the pump to the carbs. Notice the part of the bowl casting they attach to appears to line up with the little orifice I circled in red. That may be where the carbs gets a little squirt of fuel from the pump. Maybe someone with more carb experience will chime in if they have seen them. Ed

So... after cleaning that up, and slapping it back together, i get a new piece to the puzzle. When i switch the petcock to PRI carb #1 just starts dumping fuel. i thought it was only when i was turning it over, but it seems like something is just stuck wide open... not sure what it could mean though.

It's most likely one of the 3 things I listed in the posting above, or the float was installed upside down or there was some other assembly problem. Ed