Help me find the problem here. (fuel leak)

This is my first KZ, so bear with me as I learn the ropes (and quirks) of these legendary bikes...

1983 KZ750 LTD K1. Twin.

My bike has been running well for the past month. Been riding it to work etc. Apart from an oil leak on the flywheel cover there have been no problems whatsoever.

Well I come home from work one night and park the bike in the garage. The next morning when I come into the garage the entire thing reeks of gas. There is a small pool under the bike and when I look for the leak, I find that the no. 2 air filter is soaked with gas and dripping.

At first I assume this means the no.2 float level is stuck, so I take the carbs apart. But everything looks fine to me.

Then I notice another anomaly. While I have the carbs off, the exposed vacuum hose leading to the petcock is freely dripping gas. Now, I have had the carbs off countless times in the past, and with the petcock set to "ON" I have never recalled seeing this hose drip any gas, other than what was already in it when I took it off. I even tried shoving the hose up under the gas tank, sticking straight up, and the gas still comes out the top and drips down the hose.

At this point I'm guessing the petcock is trashed. However before I shell out however much cash for a new one, I have three questions:

1) Is it a bad petcock? Or am I missing something else? Carb? Fuel line?

2) Assuming it is the petcock. Is it necessary for me to buy a new one, or can I repair the old one?

3) What is a good place to find a new petcock for this bike?

sounds like its time for a petcock rebuild

can rebuild the petcock go to z1 enterprise should have what you need

Understood.

I disassembled the petcock today and took a look at it. The diaphragms look a little beat up but they seem intact. Not so sure about the plastic buffer though. There might be a chunk missing out of it.

At any rate I cleaned out all the debris and lubed all the parts and sure enough, when I hooked it up to the tank it was still dripping at the "ON" position. Shucks...

Would it be cheaper to rebuild the existing petcock or just get a new one altogether? I was thinking about putting on one of the chopper universal petcocks anyway, and they cost under $30...

A stock type vacuum petcock is your friend, you don't want to empty the tank into the engine when the float valve sticks open when the bike is parked. Nobody always remembers to shut the fuel off.

You can't always tell if a diaphragm is good by looking at it. The one on my 81 650 looked perfect but was defective.
Something you can try is to disconnect the fuel line from the carbs to see if it leaks (petcock set to ON or RES). Connect longer tubing & route it to a container to collect the fuel. A plastic juice container w a small opening will cut down on fumes.
KZR topic - Manual fuel valve option

I RECENTLY TOOK MY CARBS APART AND FOUND OUT THAT MY FLOAT BOAT WAS LEAKING BECAUSE OF A STOCK NEEDLE. TRYING LOOKING THERE AND MAKE A GASKET TO PUT BETWEEN FLOAT BOWL AND CARBS. KEEP RUBBER GASKET ON THOUGH

Hatchet wrote: Understood.

I disassembled the petcock today and took a look at it. The diaphragms look a little beat up but they seem intact. Not so sure about the plastic buffer though. There might be a chunk missing out of it.

At any rate I cleaned out all the debris and lubed all the parts and sure enough, when I hooked it up to the tank it was still dripping at the "ON" position. Shucks...

Would it be cheaper to rebuild the existing petcock or just get a new one altogether? I was thinking about putting on one of the chopper universal petcocks anyway, and they cost under $30...

Do check for pin-hole leak in petrol tank, you will see it with tank off!
Also check for leaks in petrol cock itself, just where the brass tubes are pressed into the alloy.
However, the fact that your air cleaner was soaked would indicate it's probably neither of the above.
Good luck... RegardZ.