TOPIC:

I've been trying to troubleshoot some issues with some gas fumes in my garage. [kzrider.com/forum/13-bike-related/611198-gas-fumes/]

In the process I've discovered one of my float bowls is filling up with gas even when the petcock is in the off position.

This is a 1979 KZ750 twin. The petcock isn't like ones I'm used to on other bikes. It only appears to have one replaceable o-ring and it's the one that goes around the lever. [www.kawasaki.com/Parts/PartsDiagram/143402/1979/KZ750-B4] The actual part that does the switching from reserve to off to on doesn't appear serviceable. And note that the petcock has two outlets, one for each carb.

I replaced the o-ring that I can replace, but that hasn't fixed the problem.

The float valves were replaced three or four years ago. I guess I'm trying to figure out if my issue is likely in the petcock or the carb?

Are there parts inside this style of petcock that wear out?

I'm trying to

To your question about which is leaking, the likely answer is both. An easy way to test the petcock is to turn the petcock off, disconnect the fuel lines at the carbs and route them into a clean jar or can. Once the fuel in the lines has been drained, empty the container and place the lines in it again. Leave it alone for a while, then check to see if there is any fuel in the container.
The simple answer on the carb is, yes. If the float valve was sealing properly, and the fuel level has been set properly, there would be no overflow, even if there was no petcock at all.

My petcock is the graduated type. It would weep fuel when shut off. I bought a aftermarket one and it didn't last. I took a closer look at the stock one and found tiny scratches on the plastic valve from debris in the tank that got past the strainer screen in the bowl. I fitted a pencil to the valve end so I could spin it with my cordless drill. I used #400 paper on a flat stick to polish out the grooves then used the paper that I twisted so it would fit the taper in the body and polished out the scratches in the bore. It worked. I used the same method on the float needles to remove the shoulders. I know I need another petcock and would rather have a stock one over a aftermarket one. The stock ones last for decades where the aftermarket last 1-2 years. Been looking at the Pingles but unless I can keep my reserve I won't buy one.
Steve

I think I may need to look at an aftermarket petcock if there aren't any replaceable parts in the petcock.

Pic of what you have?
Steve

In the past, I had a couple of issues with overflow. First issue I had, after resurrecting the bike, was a hairline crack in the float bowl overflow tube. Fixed that. Later I had both the petcock and the float valves were leaking. Purchased a new petcock ,witch fixed that problem. I then lapped the float valves using polishing compound and a drill at low speed for a 15 seconds or so. Never had an issue for 5 years until recently. The petcock started leaking a bit when I close it after a ride. This leak is external and not internal to the carbs. Only does a few drips for a second or two. Plan on going back to a factory petcock witch I had purchased sometime ago.

Here's my petcock. When I disconnect the fuel line and set the petcock in the off position I don't see gas dripping but it must be slowly seeping by because overnight one carb will fill up.

So I guess my main question is, is there anything inside I can service or should I just get an aftermarket replacement?

I've tried pretty much everything to fix the leaky petcocks on my Z1's. Gas leaks around the little plastic valve behind the arm. Lately I've been running the bike with the petcock closed for the last minute or so before I pull into my yard. This provides enough space in the bowl for fuel that leaks past the petcock valve.

I'm like Steve...I like the original petcocks. But if you want to eliminate the leak you should purchase a new one. I hear Pingel are the best but I've never tried them. Before doing so I would suggest you look on Partzilla to see if the OEM ones are still available.

Topper wrote: Here's my petcock. When I disconnect the fuel line and set the petcock in the off position I don't see gas dripping but it must be slowly seeping by because overnight one carb will fill up.

So I guess my main question is, is there anything inside I can service or should I just get an aftermarket replacement?

That's the same type we have. You might try my method and if it doesn't work buy a new one. The problem I'm having now is the screw cuts into the slot it rides in making it hard to turn. If I buy a aftermarket one it will be from z1parts.net
The best return policy in the business. LIFETIME WARRANTY
Steve
OUT OF STOCK
z1parts.net/zinc-fuel-valve-z1-kz/
IN STOCK. I DON'T MIND THE BLACK
z1parts.net/1973-z1-black-fuel-valve/

So, mine has a rear outlet and a right outlet. These replacement ones with two dual outlets look like one of the outlets would run into the top of my carb. Has anyone converted from a rear/.right to a dual rear?

Also, if I'm shopping around, anyone know what size petcock I should be looking for?