Float needle issues, 1980 KZ750 LTD

I decided to test the float needle by hooking up the gas with the bowl off, manually holding the float up, and it sealed perfectly. Turns out that the gasket was leaking. The gasket is brand new and in perfect shape, so I hit both surfaces with a polishing wheel on a drill to clean the area, applied some rtv and replaced the float bowl. This slowed the leak, and now it only drips while idling, and at a much slower rate. I think my float bowl might have a hairline crack or something at the top. It is definitely leaking from higher above the overflow spout. I'll try and switch the float bowls tomorrow and see if the problem persists. It's definitely not the float/needle/seat that is leaking though

Until you perform this test you cannot really know where the float is regulating the fuel level.


This positive fuel level will give you the symptoms you're experiencing. Choose the smallest diameter tubing for the downward trending section so that no air bubbles are trapped in the tube with the fuel else you will not get a true reading. Do you have a service manual? It will tell you just where the fuel level is supposed to be.

Bill

astark wrote: I decided to test the float needle by hooking up the gas with the bowl off, manually holding the float up, and it sealed perfectly. Turns out that the gasket was leaking. The gasket is brand new and in perfect shape, so I hit both surfaces with a polishing wheel on a drill to clean the area, applied some rtv and replaced the float bowl. This slowed the leak, and now it only drips while idling, and at a much slower rate. I think my float bowl might have a hairline crack or something at the top. It is definitely leaking from higher above the overflow spout. I'll try and switch the float bowls tomorrow and see if the problem persists. It's definitely not the float/needle/seat that is leaking though

You really need to perform the clear tube test to determine the fuel level in the carb bowls. If you have fuel leaking from the gasket between the bowls and carb bodies most likely the fuel level is set too high. When the bike is upright, the fuel level should remain a couple mm below that gasket, so you shouldn't have fuel leaking there at all. Also, it is important that you check your motor oil (sniff test, etc.) to see if fuel has contaminated it. With the fuel level as high as the leak suggests, fuel will run through the intake runners, past the piston rings, and flow down into the crankcase. This render the motor oil ineffective as a lubricant and can easily cause damage to the engine's internal parts. I would not start that engine again until I first corrected the fuel level problem and then changed the oil & filter. Ed

After going through and eliminating all the possible sources for the leak I've tracked it to the fuel rail between the 1st and 2nd carburetor on the left side. It seems as though its coming from the rail that delivers the fuel to all the carburetors. Has anyone else had issues with this? I'm going to get some clear tubing and test the float heights too, but its definitely leaking from above the float bowl.

I had the same sort of issue with cv34s leaking, turns out they are prone to the overflow pipe in the float bowl getting hairline cracks causing leaks check this after verifiyng float height is correct with the clear tube method.