Petcock questions

Fuel petcock question
(NOTE: I don't want a Pingel petcock; I want to use a vacuum operated unit.)
I do have two KZ1000J here with OEM petcock that works perfectly so I know those vacuum operated units can fulfill their goal.

I'm currently restoring a 1983 KZ750L that have a leaking OEM petcock ("reserve" and "on"). "Prime" works as it should. I first tried to replace it with a complete (eBay chinese) one but it also leaked as described above. I took the OEM unit apart (rubbers were worn out) and installed the chinese's inners inside the OEM one (after a deep cleaning). Same leaking. I even shimmed the vacuum spring for a stronger closing force but it leaked up to the point it could not open anymore under vacuum…

Then, I ordered a petcock repair kit (still eBay chinese) that I received today. I installed it and same leaking. After a few (well, more than a few) curse words, I don't know what to do next.

I do have another spare OEM off a 1982 1000J that I could try to use (possibly with that repair kit I received today) but I'm not optimistic…

Are Chinese really unable to make leakproof petcock or repair kit? Does only OEM parts that works? I could order OEM's 43028-1015 diaphragm but will it work?

This 750 is a bike I intend to sell so I don't want to spend a ton of money on it.

Thanks!

Kawasaki 43028-1015 - TAP DIAPHRAGM | Partzilla.com

My first choice is always OEM parts if I can get them. Lately, I've been purchasing rubber parts from  Sumo Rubber  They seem to have a good reputation. 
Also, rebuilding petcocks is more than just replacing the rubber bits. This tutorial is for Yamaha petcocks but lessons apply to Kawasaki as well  Rebuilding vacuum operated petcocks

By MY experience, ALL eBay petcocks leak. 
 

I had the same problem as you do, Claude, for my KZ750 LTD H2.
Petcock leaking despite a replacement kit for the rubbers and diaphragm and several cleanings of the inside of the petcock.
I then decided to buy a suzuki petcock that somebody recommended on the forum. It worked well but I was a bit annoyed at not being able to rescue the original petcock.
Recently, I let the old petcock with new rubber parts seating in a bowl of fuel for a night and tested it the next day.
I guess that the rubber swelled because the petcock now works perfectly ! I put it back on my tank and it has not been leaking a drop since.
Maybe give it a try
And do follow the tutorial posted by ThatGpzGuy, I did exactly that, cleaning as best you can all the parts to make sure it seals properly.

ThatGPzGuy wrote:

My first choice is always OEM parts if I can get them. Lately, I've been purchasing rubber parts from  Sumo Rubber  They seem to have a good reputation. 
Also, rebuilding petcocks is more than just replacing the rubber bits. This tutorial is for Yamaha petcocks but lessons apply to Kawasaki as well  Rebuilding vacuum operated petcocks

Good reading! I did some of the steps but not all. I will redo the rebuild including those steps. Thanks!

blipco wrote:

By MY experience, ALL eBay petcocks leak. 

 

So sad that the chinese can't reproduce a good design... If they were half the price with good design instead of one quarter the price with a bad design, they would be a much better option.

Michel3007 wrote:

I had the same problem as you do, Claude, for my KZ750 LTD H2.
Petcock leaking despite a replacement kit for the rubbers and diaphragm and several cleanings of the inside of the petcock.
I then decided to buy a suzuki petcock that somebody recommended on the forum. It worked well but I was a bit annoyed at not being able to rescue the original petcock.
Recently, I let the old petcock with new rubber parts seating in a bowl of fuel for a night and tested it the next day.
I guess that the rubber swelled because the petcock now works perfectly ! I put it back on my tank and it has not been leaking a drop since.
Maybe give it a try
And do follow the tutorial posted by ThatGpzGuy, I did exactly that, cleaning as best you can all the parts to make sure it seals properly.

Rubber swelling... Didn't thought at this! Will try it for sure before putting it back on the fuel tank. Thanks for sharing!
Now I'm wondering if the eBay units could seal after a one day "fuel bath"... Hmmm...

I rebuilt the petcock for my 750E, using OEM Kawasaki parts, and it works perfectly.  Kawasaki doesn't sell a "kit", you have to order the parts separately, but everything seems to be available.  Obviously, each petcock is different, and I'm sure the parts support is spotty at best across different models.  

P1010520 by nessism , on Flickr

Nessism wrote:

...Obviously, each petcock is different, and I'm sure the parts support is spotty at best across different models.  

P1010520 by nessism , on Flickr

I'm always wondering why they are different from one model to another. As an example, p/n is different between my KZ750 and my 1000J. But by looking at them, they are virtually identical. I assume the height of "reserve" built in the plastic "filter" could be different but everything else looks to be interchangeable. I also think, that event if both have different p/n for the diaphragm, both seem to have the same dimensions and, theoretically, should work the same exact way. So, why make the diaphragm different??

I can think of a couple of reasons for differences in parts. First has to do with supply of the parts in question and the cost of said parts.  Secondly it may of been that a change in design had to so with some type of improvement or at least preceived improvement.  But I would think it had more to do with cost and supply.  But what do I know?

Just finished rebuilding "again" the petcock.
As written in the link posted by ThatGPzGuy (thanks again!), I polished the o-ring seats sanded (with 600 grit) some mating surfaces and shooted silicone spray on the rubbers.
The assembled part is now soaking in a jar filled with gas. Will install it back later, hopefully this week.

Only thing I noted is that the "vent" built in the plastic plate (over which the diaphragm but be installed) can not be installed on the lower edge. Because of small pins molded on the plate and small holes present in the casting, the only way the vent can be installed is on the lower half of the read edge. My other spare petcock (that I believe being from a 1000J) is also assembled that way.

Thanks again for every comment!

You can order a OEM replacement direct from any Kawasaki dealer - see below for the PN (this example is a online reseller) :

www.cmsnl.com/kawasaki-kz1000p24-police-...assy-fuel_510231375/

Or another example from a online reseller :

www.z1enterprises.com/petcock-kz1000k44-...0-kz650h-kz750h.html

They are a bit expensive but they are made in Japan, and you can get the repair parts from Kawasaki Canada going forward.

Stay away from made in "China" petcocks because you can't reliably get replacement parts.

Kawasaki used a lot of different style petcocks over the years, they look similar but there are internal differences so these "rebuild" kits out there are hit or miss - mostly miss