Copper oil sealing shim

 Here I'm again with the leaky sieve that I sometimes call "motorcycle
engine", from my air cooled DOHC 24hp 250cc Honda X-something.

Atop of the left side (clutch) engine cover, there is the typical oil
banjo bolt, just like the ones that are widely used for brake lines,
just that this one is what carries oil from bottom end, directly from
oil pump, to engine head.

After I did a top end rebuild, I ended up with oil leaking from a few
parts - I've posted about that here - and one leak persists, from that
banjo bolt. JFTR, before doing the top end, I had zero oil leaks (*),
this was the second (**) top end of this engine and I did both.
Yesterday I decided to remove the banjo bolt and inspect it. I found
that the shims were crushed, so, even though they were crushed before
and not leaking, I decided to take'em to the #360 sandpaper and make
then flat again. The leak persists. Do I have to change the shims?
Never heard that those copper shims were "wear items", as though
everything in my bike are wear items because I really really really
abuse it. It's not loose, one quart of turn more the banjo bolt either
breaks or the threads strip. Not leaking a lot, just "sweating" oil,
this oil is staining the entire engine, due to air flow, I guess. The
engineering of the air flow must be very good, because it managed to
spread oil over several cylinder fins, making me almost nuts searching
for the source of the leak.

Any hints I could use? :-)

-- Tiago
(*) there is one very small leak on a magneto cover screw, but I don't
want to replace the entire cover ($$), it leaks so little it doesn't
worth the trouble and expense.
(**) the first time was rings only, this second time I had to go 1
step oversize with a new piston. I should have gone 2 steps, because 1
step over didn't clear all the marks on sleeve.

 On Mon, 29 Jun 2009 10:55:07 -0700 (PDT), Tiago


Hey Tiago,

Those washer you are talking about ar commonly called "crush washers"
due to the fact that they seal when crushed.  Sometimes you can reuse
them, and sometimes you cannot.  My streetbike will get a new one on
the oil drain bolt every oil change for safety reasons.  

I would purchase replacements.  If the leaking got worse when you
tightened the banjo bolt, carefully inspect the banjo fitting for
cracks.

Mike Baxter

 
Thanks Mike!
I'll check the repair manual, but when manual says "replace", I almost
never do, they are way too... let's say "overkill"... Lots of stuff
are reusable. Do you know what? The oil drain bolt on my bike: I had a
worn out 12mm "L" and long time ago, when bike was still "new", I
managed to destroy the head of it. In the proccess of installing the
replacement, I lost the copper shim of it and it is, since (I guess,
iirc) 2003 without that shim and it doesn't leak and nowadays I don't
get that bolt tight, it's hand tight + 1/3 turn. Re: the banjo bolt in
question (which is on the **right** side engine cover, sorry, not
left), the shims are the same when Honda built the bike in 2002 and
I've had the clutch apart lots of times, never replaced those. But
seems that indeed have to be replaced sometime... I already guessed
that they had to be replaced, but wonder why they lasted 7 years and
several install / uninstall without leaking...

I hate oil leaks, I really do... Besides every brand of hi temp
silicon and every type of liquid gasket available, I tried alluminum
powder with two-part epoxy glue (araldite is my favorite) on the
magneto cover leak, no work, still leaks. If it wasn't so much work
(no, I'm not *that* lazy), I'd have that screw hole welded shut and I
would redrill it...

-- T

 On Mon, 29 Jun 2009 12:39:51 -0700 (PDT), Tiago

<snip>

http://www.motorcycle.co.uk/Reference-material/Annealling-Copper---Aluminium-washers.aspx

<quote>
Or, making your oil-tight washers oil-tight again.

So you've dropped the oil from your engine / gearbox / forks / bevel
drive, and you realise you should have bought a new washer for the
drain plug cause the old one looks a bit squashed. Will it seal again?
Will you over-tighten (and strip!) the drain plug getting it to seal?

Better to re-anneal the washer if you are going to re-use it.

Why? - When you 'work' copper or aluminium, it goes hard. Tightening
an oil-drain plug against a washer 'works' the metal. 'Annealing'
means 'making it soft so it deforms again'.

Here's how....

Grab 2 pairs of pointy-nose pliers. Wipe any oil/grit off the washer
and take it into the kitchen. Erm, you do have a gas cooker, don't you
?
(Alternatively, gas welding kit; blowtorch; or some other source of
safe flame. A cigarette lighter isn't enough heat, a hot air gun won't
do it either. A gas cooker is the thing you want. A camping stove will
do.)

You need to get it hot enough, but obviously not melt it:

Copper: which you recognise because it is copper-coloured.

You need to get copper 'dull red'. Dull Red is one of those technical
terms engineers use. It just means roast it until it glows a dull red.
In order, as you heat metal, it goes:

    *    slightly reddish tinge - this isn't hot enough to do anything
    *    dull red
    *    cherry red - properly 'red', but somewhere less than orange
    *    orangey-yellow - way further than you need to go
    *    white-hot - its about to melt, stop it.
</quote>

 

http://www.motorcycle.co.uk/Reference-material/Annealling-Copper---Aluminium-washers.aspx

you forgot the part about quenching it in water

The British bikes like Norton have those I believe they also have a copper
head gasket.  you can go aluminum but that doesn't anneal the same.  I know
from experience you can break the banjo bolt before getting the leak to
stop.  New is probably best.

Fran