stopping gasket leaks

The gaskets don't leak, but o-rings do. The KZ650/750 uses 1000 o-rings, and over time they all will eventually leak, so wherever it's leaking it will be an o-ring. One of the bad ideas in design vs the 900/1000 and probably the worst point of any KZ650/750.

So how much squish should an o-ring have? 
The last time I had the head off my bike, I measured the depth of the o-ring detents in the cylinder and the thickness of the head gasket, and it left little to no squish for the o-rings that came with rebuild gasket kit. I discarded those o-rings and used slightly thicker ones.

ckahleer wrote:

So how much squish should an o-ring have? 

For face seals O-ring manufactures recommend 20-30% compression of the original cross sectional diameter.

Thank you to everyone for all the tips and advise. I'm back from the holiday out of state so picking this up as I hope to get this fixed ASAP if at all possible. If it turns out to be a big job, it will wait for winter. If O-rings are the likely culprit, the tachometer output should be fairly easy to check. Since I'm not at the bike right now, where does the cable go in? Secondly, what is the best way to use talc to look for leaks? How do you get it on the engine without messing up too much? Thirdly, is there a list in the Clymer manual or somewhere where all the O-rings are located? Tachometer is not in the index..

dewy0823 wrote:

Thank you to everyone for all the tips and advise. I'm back from the holiday out of state so picking this up as I hope to get this fixed ASAP if at all possible. If it turns out to be a big job, it will wait for winter. If O-rings are the likely culprit, the tachometer output should be fairly easy to check. Since I'm not at the bike right now, where does the cable go in? Secondly, what is the best way to use talc to look for leaks? How do you get it on the engine without messing up too much? Thirdly, is there a list in the Clymer manual or somewhere where all the O-rings are located? Tachometer is not in the index..

Sprinkle it where you can, where access is difficult you can put it on a piece of card and blow it into the suspect area with your mouth. Don't worry about mess, it will wash off with a hose pipe. The reason for the powder is it won't run so will identify the spot that is leaking

You can find most of them by looking through the parts diagrams.

www.partzilla.com/catalog/kawasaki/motorcycle/1982/csr-kz650-h2

Note that the tachometer drive has an oring, a fiber washer and a seal.

www.partzilla.com/catalog/kawasaki/motor...ad-cover-81-82-h1-h2

I wouldnt be surprised if the half moon on the left side is leaking. They leaked on both my 1000 and 550. After sitting they would leak down the fins and then make me think my bike was on fire when I came back to it after warming up!

If you checked valve clearances and hit one of those rubber moons, it might not be sealing anymore. In my experience if you ever tamper with those 45 year old rubber, it'll never seal again.

Thx Bound. The engine has never been opened up so I've not checked head bolts, gasket or valve clearance. Exactly where are these half moons so I can apply talc to the area to test today and what is necessary to fix or replace them? I have the Clymer manual and don't know what to look for to see what's involved.

These are the half moons 
I would find the source of the leak first like what others recommend before replacing anything. If the half moons are the source of the leak you might be able to find them on z1enterprises.com 

The Elephant in the room but noted by the Guru of 650's, All Hail RonKZ650!! Here's the worst case scenario as mentioned previously. Sandwiched between Head and Cylinder lies a couple oil correction orifices and their sealing orings. Check for leaking oil from the center/outer on both sides. All the other stuff is a piece of cake to rectify. But..if it's blowing oil out within these areas as Ron mentioned, NO EASY fix. Picture to show You what to look for, have FuN! And NO you can't just slather some silicone or JB Weld on the leaking joint. It'll just pressurize around such behavior and start leaking somewhere adjacent. Have to realize these engines were Hi pressure, not like the more forgiving Hi Volume of the 900/1000/1100's.       

Thx everyone. I've got talc so Sunday afternoon, I hope to find the leak(s). Then I'll go with the info you guys provided, Pics are very helpful. Thx.

I assume I clean the oil off first with brake cleaner, then put the powder on before I ride for the test. yes? BTW talcum powder is pretty much NA since it's known to cause cancer. Will baby powder or talc free foot powder or body powder work? Thx.