1978 KZ650C2 petcock woes

Vacuum Petcock = Junk

An interesting read.I had no idea that Kawasaki vacuum taps were so divisive.I just fitted a rebuild kit in mine. So far it seems to be holding.
I found this page very helpful;
xjbikes.com/forums/threads/rebuilding-th...-valve-w-pics.25058/

Clearly, somebody needs to carry the flag for big K.

I have been riding off and on for almost 50 years, regularly for the last 25. I have owned more than a dozen bikes, all but two have been Kawasakis. In all that, I can recall only four vacuum petcock failures.

One was totally my fault for leaving the bike unstarted for nearly a year.
Another was my fault for using a cheap aftermarket kit.
One failed after only 50,000 miles.
The other was so long ago that I don't remember the circumstances.

I wish the factory shocks were that good.

davido wrote: An interesting read.I had no idea that Kawasaki vacuum taps were so divisive.I just fitted a rebuild kit in mine. So far it seems to be holding.
I found this page very helpful;
xjbikes.com/forums/threads/rebuilding-th...-valve-w-pics.25058/

Scrap that.I just went down to work on the bike and found a petrol lake under it AGAIN! Im now stinking of petrol as I tried to pull the tank and the fuel pissed out of the tap all over the place. I am Not Happy. WTF!!!!!!!!!!!!!!!!!!!!!!
One step forward two steps back.This bike is doing my head in.

davido wrote: .........I just went down to work on the bike and found a petrol lake under it AGAIN! Im now stinking of petrol as I tried to pull the tank and the fuel pissed out of the tap all over the place. I am Not Happy. WTF!!!!!!!!!!!!!!!!!!!!!!
One step forward two steps back.This bike is doing my head in.

One more example of why I really like my manual petcock. When you turn it off fuel will not flow. There are no diaphragms in it, so they cannot fail. Ed

Yup,Thats what I have on my 500/4. Never had any problems with it. Then again,my CBX750 has a vacuum tap and Ive never had trouble with that either.

Of course a puddle of gas under the bike means the needle/seats in the carbs need replaced in addition to petcock failure, unless the diaphram failed in a rare way allowing gas to flow down the vacuum line. I don't think this is possible because of the check ball in the vacuum port of the petcock.
Yes, the petcock sticking on is an aggravating problem. It has happened to me a couple times for sure, but the simple replacement of the diaphram for $13.00 is a simple job. Petcock doesn't even have to be removed from the tank.
The manual petcock problems for me was probably that I rode 3 miles to work, shut it off, go to lunch, turn it on, then off again, then on again and off to go home, so every single day I was turning on/off at least 3 or 4 times. Probably a guy that rides on a Sunday that turns it on/off less frequently it is fine. On mine, even if greased about every 2 weeks, the lever would wear the bore from constant turning, gas would start to leak, then grease would be needed every few days. Don't grease, and the lever gets stiff and snaps off. I snapped off like 5 levers on different petcocks. For me, the once in a while sticking vacuum diaphram was much easier to keep working. This is all KZ650, on my KZ1000MKII, I have 80,000 miles on it with the vacuum petcock and it has never given a problem.

There is this thing called maintenance. Try it sometime. Your bike will thank you. Things like replacing the rubber parts inside your petcock are not typically on most people's radar screen but they must be done regardless Just like replacing the rubber O-rings inside the carbs. You can't expect rubber parts exposed to gasoline to last indefinitely. After 30 years they need some attention.

Thanks All.
I had called a few Kawasaki dealers in Canada who told me no petcocks or rebuild kits/diaphams available - I have sine learned that I can order a $13 diaphragm online - thanks to this discussion - which I will do and keep an eye out for a manual replacement if available...thanks

Do you know of a manual petcock that will fit the 1978 KZ650 C2 ?
I'd love to get one!
Jake

Here's a picture showing the spacing for the mounting bolts on the 1977 K650 manual petcock. If the spacing is the same as your 1978 petcock spacing a petcock from a 1977 KZ650 will work, but finding an unmolested or new one might take time. There was a place in Germany making exact replicas, but I haven't seen them offer one recently. Ed

Put a 77 manual on my bike back in 81 after failure upon failure of the stock vacuum one, on the recommendation of the local Kawasaki guru
It's still the same one in my tank today. Nothing has ever wore out :huh: Yes there are a few rubber parts that need to be replaced here and there, as someone mentioned maintenance :ohmy: Over the years I've probably averaged 10 or more times a day turning it off/on
Just the look of a diaphragm from a vacuum one is sketchy AF and that is how they work. or don't work I guess would be more accurate

When my son bought a 78 650SR like mine the 1st thing I did was buy a 77 petcock off of ebay, tore it apart cleaned all moving parts with fine Scotchbrite, replaced all the soft parts and installed it. It is still working fine after 6 yrs.even the soft parts have yet to be replaced. That is a miracle in my eyes considering the sorry state of what is sold for gasoline nowadays

Old time real gasoline used to destroy those diaphragm, can't imagine how they survive today
To me if you are so lazy that you can't turn off a petcock when you park, you should seriously consider sticking to 4 wheels

EZ