petcock stuck on vacuum

Hi all, I know much has been written about petcocks here, but I can't find something on quite this issue.
I have a 1980 KZ650 F1, with the auto vacuum petcock. It has been leaking gas. I opened the back of it up, and the diaphragm was sucked in, letting the gas flow through, as though there was a vacuum being applied on the vacuum port, though there was not. I guess the vacuum inlet was clogged up, or the check-valve that is in the vacuum inlet was clogged. I cleaned out that vacuum inlet with carb cleaner, reassembled it and it seemed to work perfectly fine. A couple days later it was leaking again. Opened it up, didn't do anything, put it back together and it worked again. Does anyone have an idea of what is going on here? I can get a rebuild kit, sure, but I don't think that addresses what's going on here. Maybe I just need to clean out the vacuum inlet again? I thought I had sprayed the hell out of it with carb cleaner. I don't quite understand why there is a check valve in there anyway.

Your manual will show you if you have one.
Steve

Yep, definitely have a vacuum petcock, thanks. Thoughts as to why it's getting stuck in the sucked-in state?

There should be a spring in there. I was suggesting the manual would have a diagram of it.
Steve

Ah, right. Yes, mine has a spring. I stretched it out some, though even before that, it did seem to work fine after I relieved the vacuum by taking the diaphragm off and then reassembling it.

You shouldn't stretch a spring. The vacuum shouldn't be there with the engine off. You really do need to get a manual.
Steve

No eBay APP ID and/or Cert ID defined in Kunena configurationOver time the modern fuel with 10% alcohol eats away at the rubber parts in your petcock, the round part that has the 5 holes is the one that usually screws up on mine, it's the gasket that goes behind the selector lever.
My advise to you is buy the kit and be done with it .... for now.

:whistle:

Might be the small o-ring seal on the post in the middle of the diaphragm. If it has a rough spot or has softened due to contact with fuel, it can stick. Be careful about the cleaner you use, some of them attack rubber.

80 650 F1 - petcock parts

check to make sure the diaphragm and all other parts are in the correct orientation (check for gas hole to correspond with the other parts) - may just be staying open because it can't find air to snap back.



I rebuilt mine last year (slightly different than yours, but still vacuum style). These are the parts, alignment is necessary for the PC to function properly. Take note of the small plastic pins on the part to the right.

I've fought this a couple times over the years, and being a mechanical kind of guy, I was not going to let this simple system get the best of me, but it did. What I found was the diaphram, spring, oring ect. All of it may look fine, you can clean, lube and otherwise spend effort for hours, and all for nothing. Buy a new diaphram and be done with it. I found the original Kawasaki diaphram was like $13.00 last time I did one. I never, ever had problems after replace of the diaphram. Others have reported no luck replacing the diaphram though, so mileage may vary, but it has always worked for me.

They get hard and lose their elasticity. O ring should be replaced at the same time.
Steve