Cylinder Head Nut's Washer ...

[Mr.humbucker]

The four chrome cylinder head acorn (my term?) nuts have what appears to be a copper washer beneath it. Can someone tell me why it isn't a "standard" washer? Just Curious ...

[eil]

Oil flows up around those studs to get to the cylinder head, the copper washers are seals.

[Steve]

"Seal", "gasket", whatever you want to call it, yes, it keeps the oil inside the engine.

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[Mr.humbucker]

Well, my day is complete and now I know! Thanks for the quick replies!

[Steve]

And now for the REST of the story.

Oil comes up around the two rear studs. That is why you have an oval o-ring around them at the base gasket. Oil travels up around the stud through the cylinders. When it gets to the head, there is an angled passage that takes it to another passage that runs under the intake cam bearings. There is also a passage in the head that leads to a similar cam bearing feed for the exhaust cam bearings. All those passages also go around the two outer studs on each side, so they need the sealing of the copper washer. It's pretty much like the copper crush washers in the brake line banjo fittings.

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[Brendan W]

If you are putting old ones back, check they aren't too deformed.
It's copper but there are limits

[Mr.humbucker]

The old copper washers were in great shape, I cleaned them off and put them back in place. Thanks again to all. I have only done a partial teardown of one of my bike engines and learned a bit from that. I think I'll keep my eyes open for one that someone is getting rid of (cheap) and will take it completely apart to see what I can learn/understand from seeing inside.

On the subject of brake line banjo bolt copper washers, I've bought new break lines recently that came with new bolts and washers. I don't recall them being obvious copper coloured (Canadian spelling) washers. Could they be using something else? And (the bonus question) is there a difference between copper crush and copper washers or are they one in the same?

[Brendan W]

There are flat, rectangular section, solid washers like what you have on the bike and there are rolled round section I would call a crush washer.
Different people probably call them different things.
Unfortunately, like anything else these days, more and more parts are manufactured down to a price. They could be anything. Aluminium in particular is used a bit to replace the traditional copper.

[GregT]

Your silver coloured washers with the brake line components are aluminium crush washers. Aluminium because the tightening torques on line fittings are low.
They should only be used once - in theory.

[Grimly]

If you re-use copper washers, especially for brake lines, re-anneal them by heating them up in a gas flame and quenching them in water.

[Mr.humbucker]

If you re-use copper washers, especially for brake lines, re-anneal them by heating them up in a gas flame and quenching them in water.

This is very useful and informative. I am/was not familiar with the term anneal and so ... I did a bit of interneting 101 and went to this link to learn more: https://en.wikipedia.org/wiki/Annealing_(metallurgy)
I think I would have done better in school (not that I did bad) if we would have had practical projects to learn from like working on these old bikes. I've learned a lot here - thanks again!

I'll toss out another question here, I am having a bit of difficulty getting the oil plug/drain bolt to seal on one of my bikes. Is a copper washer or crush type a good option here or is there a rubber synthetic seal system/washer out there that is recommended?

[cowboyup3371]

This is what you need for the oil pan bolt - it's essentially a crush washer but called gasket:

From Parts Outlaw
GASKET
09168-14004
$1.05