CARB 1 OVERFLOW

1983 KZ750 LTD- pods, jetted 140-70, MAC 4-1 loud as shit

Seriously getting to the point where I may take bike to a shop. After cylinder 3 was not firing, cold header, I took my time and rebuilt carbs (had been sitting while I was at school, stored dry but since had the tank relined due to rust, thought maybe something had clogged up the carb after trying to start)

Rebuilt petcock, installed new gas line, installed carbs, went through ignition wires, cleaned spark plugs, took a breath, put the tank on, filled with gas, put petcock to on.

While I was hooking up battery to charger to start (another post to come for that one), gas appeared on the floor. A steady ball-point-pen sized stream was going on to the floor from the overflow tube on the left side of carbs. Awesome. Walked over to that side and BAM saw this:




Carb 1 is flooded, understand that my floats aren't working. May work up the nerve to go back out and check, just need to come down off this gas-high.

Spare some wisdom ye who know best.

Your CV carbs may be a little different, but here's some advice for overflow problems....

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 reoccurrence 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

awesome thank you 650ed

Malfunctioning overflow circuit is allowing raw gasoline to puddle in #1 carb throat.

Raw gasoline in carb throat may find its way into the crankcase, whereby the oil becomes diluted and contaminated by gasoline.

Would sniff-test the crankcase oil and physically examine the oil.

If the crankcase has become contaminated with gasoline, should drain the crankcase, and change both the oil and filter.

Meanwhile, don't allow any gasoline to enter the carbs until the overflow circuit is restored to function.

And, of course, don't run the engine with gasoline-contaminated oil.

Good Fortune!

Thanks Patton.

Turned out it was my petcock. Had retainer washer on the wrong side of the lever. put it in the correct position and worked like a charm. Rebuild carbs, again too.