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My 1978 kz650 is leaking fuel from the petcock. Its leaking out of the side from a notch that seems to be there. I took it apart and could not find any problems. It only leaks when it is running of course. I have seen rebuild kits for 1979 and 80s but none that say they are for the 1978. Is it ok to rebuild or is there a replacement out there that will work and look factory like. I might add I am new to this forum and new to the KZ650. Would appreciate any help on this petcock issue.

Does your petcock have a diaphragm that looks kind of like a top hat? If it does, I'm not sure if the later diaphragm can be used or not. I don't think so, but I'm not sure.

It was square with spring in the middle on one side and looks like a valve on the other side. there are two rubber gasket looking seals or diaphragms in there. I assume because its leaking that there is a hole I could not see. I found a kz400 petcock on e bay that looks just like the one on my 650. is there a difference?

Here is a list of bikes that use the same one

www.partzilla.com/product/kawasaki/51023...814857815d06df0e6378

Thanks. There is a guy on e bay who makes an adapter says it fits a lot of bikes including the kz650. Im going to try one. Right now I cant ride!!

Just an fyi. The bolt-hole spacing on your petcock should be 44mm. Also, an oem diaphragm assy may be available from the dealer at reasonable cost & Kawasaki may have the other rubber parts as well. Z1Enterprises has an aftermarket Suzuki vacuum petcock that is a direct bolt-on.

Would you happen to know which model suzuki the petcock was for?

What specific KZ650 do you have? It should be either a B model w wire spoked wheels, a 650C Custom or 650D SR. The C & D have cast alloy wheels.

Z1Enterprises lists two Suzuki vacuum petcock w 44mm bolt-hole spacing. In their item description one of them has a taller pickup tube, so you would have to switch to reserve sooner. Also, they indicate that others have reported that with a 650D SR, the petcock may interfere with the frame as the SR petcock is mounted further back on the fuel tank. I wasn't aware of that potential problem. Suzuki 44mm

Adapter plate. Z1Enterprises has Pingel adapter plates for mounting a thread-on petcock. When switching to that, you may have to ream out the fuel filter hole on the tank & when doing that there is the potential for explosion if a spark is created, so use caution.

I have a 650B. Ok thanks I will look. Will a non vacuum type petcock work ok on the kz650. THe one Im getting is not a vacuum type. It wont flood the carbs?

this is one I ordered off of ebay

If the bolt-hole spacing is correct, then that should be fine. The filter doesn't look too fat, so you probably won't have to ream the fuel tank, unless the fuel valve threads are too long for the adapter plate.

With a manual fuel valve you have to turn if OFF when the engine is stopped. Some guys prefer a manual fuel valve. I prefer a vacuum petcock --- I like the automatic shut-off feature. If you park your motorcycle in a garage that has a water heater & forget to turn off a manual fuel valve, there is that potential for fuel puddling on the garage floor & gasoline vapors forming then a possible explosion. A vacuum petcock could fail & do the same, though, so you have to be aware with either type.

I understand and agree with you!!!!! Appreciate your help your bike rocks!!!!! Hear is mine. Im still cleaning on it but its coming along. If I could just ride it now. lol