Cylinder head oil leak; advice needed.

[nrml76]

I did an oil / oil filter change on my kawasaki zr7 about 250 miles back. As per castrol's and the manufacturers recommentations, I put in castrol GPS 10W-40 oil. The oil was filled to the correct level. I now notice a very slight oil smear on the right side of the engine, between the cylinder head and the engine block. I've checked the torque on the cylinder head nuts, and everthing is in order. The bike runs alright, and the oil level has not been decreasing. Having this checked out sounds very expensive to me. Any suggestions as to what can be the cause (the bike did 6000 miles before the oil change without any problems or leaks)? At the moment, I am just keeping an eye on the oil level. Any potential problems if I ignore this leak for the time being?

[Bezzer]

If the weep keeps appearing then it's the head gasket. You can still use it up to a point but let it get too bad and you might end up warping the head and other problems. It's air/oil cooled isn't it?, if so it's not as much of a problem as a water cooled engine but still needs sorting out as soon as you can.
Couple of hours labour and a head gasket at a shop, not too hard a job to do yourself as long as you can follow the manual and take your time.
More than likely just an unfortunate coincidence and nothing to do with your oil change.
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I used to be indecisive but now I'm not quite so sure.

[ZRX61]

Those engines are prone to this, it dates back to the '77 Z650. Where the oil feed goes up thru the block to the cams there is an O ring that fails.

You can't replace the head gasket without pulling the cylinder block....

Well, you *can*.. but the problem is this:
When you pull the head it releases the tension on the base gasket. If you simply replace the head gasket the base gasket will usually blow within about a month resulting in another tear down.

Most Kaw owners ignore the leak until it's time to replace the cam chain.

[Nath]

My cb550 does the same thing, for exactly the same reason. I don't really see what harm it can do by leaving it, and it is only a tiny amount of oil that weeps out.

It's actually my own fault that I have this problem, as after I'd finished messing about with the head and barrels, I refitted the old O-Rings even though they looked a bit worse for wear. At the time I didn't know that this was a problem on cb550s and since I didn't have any O rings of the right size I just went for the lazy option
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Hard livin', hard luck.