Oil leaking from cylinder head chrome nut!

Hi there, I'm a new member to your forum & have a strange problem.
I have an oil leak from the front left hand cylinder head chrome nut on my kz650. Oil seems to be coming up from the cylinder head stud & then dripping down to the exhaust after running for a few minutes.
Have done a hot compression test with perfect readings on all 4 cylinders. (12 bar)
It's definitely not leaking from the head gasket but coming from the nut in my photo.
Any pointers please. I've got a new gasket set ready.

Under the nut is a copper washer, try to smoothing the surface with a fine sandpaper to remove scratches.

I've already removed the nut to see what was underneath. There is just a plain steel washer.
Took another one off on the other side & is the same washer. No copper ones.

Shouldn't need a new head gasket.
The four outer studs act as oil galleries to the head/cams and the nuts sit on copper washers which seal against the head.
Remove the nut on the leaking stud and anneal (soften) the copper washer ( heat to cherry red and quench in clean water).
Re fit the washer the opposite way up to which it came off to give it the best chance of sealing.
If that fails to cure the weep fit a new copper washer but be sure to anneal new ones before fitment as they are work hardened from the stamping process.

No eBay APP ID and/or Cert ID defined in Kunena configurationAre the washers plated such that they do not look like copper, or is it that the KZ650 engines did not use copper washers?

I ask because they do not look like copper. They are part number 411AA1000 (see link below), and when one looks at the ones in the eBay listings (shown below) they are silver colored rather than copper colored. Given that one cannot tell if they are steel or plated copper. Ed

www.powersportswarehouse.com/p/Kawasaki#...50-C1-1977/070052B-4

Mine are copper in color.
After annealing I clean them up with scotchbrite and they appear copper again . ( Same thing with copper head gaskets )
Dave

The copper washers are a different part number and only go on the 4 outer studs. Maybe an EBay screwup using all steel washers. Or you put the copper on an inner stud by mistake.

It should be copper washers.
Copper is soft enough to balance and seal some surface defects.
It´s like a banjo bolt washer on a break line to caliper fitting.

Michael

I compare it to the aluminum crush washer used on every Honda (car) drain plug known to man.

The four outer studs act as oil galleries to the head/cams and the nuts sit on copper washers which seal against the head.

Not on these No. Smaller 550 / 750 secondary shaft series have their own oil feeds one on each end. They are designed to be oil tight -not to flow oil.

Problem is oil forced up a stud, this is covered in the UK Haynes Manual for the 550 Page 90 para 2-4. The procedure is to remove all studs, wire brush and solvent clean then refit with loctite or part number k61079-001. Maybe someone n the trade can find a dealer service bulletin covering this.

Seems a lot of work for a very minor oil leak, I prefer the copper washer anneal and retourque idea.

Thanks for all your helpful replies.
I'm away camping this weekend but will get straight out to the garage when I get home tomorrow & check the washers are actually copper.
Cheers again

Ok, just got back & first thing I did was to look at the leaking nut / washer.
The washer is steel 100% even put a magnet on to check.
I can't see anything about copper washers in my manual ( but then again, it's a Haynes !!)