1969 / 1970 S type oil tank.

Hi All.
I have two type of oil tank with different oil breather tubes on the top.
One has two breather tubes, one to connect the engine breather and one that goes free in the air; there is a hole on the air filter mount that remain close in the air filter system.
The other is the same but do not has the second tube that goes free free in the air with an hose..
What are the differences between those tanks and how they work.
Thank you.
Piero

I only know of 2 kinds. Both have open hole in front of oil tank. Only where breather spigot attaches is different. One to 'top hat' one to top of main tank. In both the open hole goes to the 'top hat' with a tube inside the tank. If the hole is blocked, the oil tank will not breathe unless another hole is made.





The one in second picture is later one, I think they changed the breather spigot to keep oil from going in the air filter breather tube?

Hi Dave,
i thought there was only two kinds of 69/70 S/Roadster oil tank but after i have seen your two pictures i can say there is a third type.
1. in your first picture that has the breather spigot attaches to 'top hat' (with tube inside the tank that goes with an open hole into the air filter);
2. in your second picture that had the breather spigot attaches to top of main tank hat' (with tube inside the tank that goes with an open hole into the air filter);
3. that i have that has the breather spigot attaches to 'top hat' and also the breather spigot attaches to top of main tank hat (with tube inside the tank that goes with an open hole into the air filter).
In both pictures the spigots (top hat/top main) go to engine breather.
But the third oil tank type (double spigots) if the top hat spigot goes to the engine breather, where goes the top main one? free in the air with a hose? yes, but why there is also the open hole in front of the tank?.
I will post a picture of the third type later.
Ciao
Piero

DogT said:

I If the hole is blocked, the oil tank will not breathe unless another hole is made.

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I have this suspicion on my oil tank.
I have an extra reed valve attached to the rear side of the timing cover and
the normal breather through the camshaft on my 70 Commando.
The hoses are connected and lead into the top hat on the oil tank.
Opening the oil tank with the engine running a while there is a sound like opening a soda can.
So I guess there is some pressure building up in the tank.
Any chance to unblock the breather line in the tank?
Or is it too much pressure from both hoses to the tank?

Is the small diameter hose coming off of the oil return line fitting for a chain oiler?

Bob,

Yes that black line coming off the supply banjo is the chain oiler. I crimped mine off and soldered it shut. That tank is a spare I have. I was going to experiment with breathers at one point but never got to it. I always had a lot of oil coming out of that hole in the front of the tank so I tapped it, put a nipple in it and fed it to a catch bottle.

rivera,

That tube from the tank front (air filter area) should be open and curve like the red line inside the tank into the 'top hat'. Maybe some bees have gotten in it and filled it with mud? I'd try to open it up. A piece of stiff wire or long zip tie may be able to break through. You don't want pressure in the oil tank, it will prevent venting from the engine, at least that's what I think.

Piero,
I think I've seen a tank with 2 spigots on it, but I don't know where. Must have been on this forum, maybe it is a transition tank? It would be interesting to know. I'd like to see a picture of it. I've rarely seen tanks like mine with the spigot on the top hat. Most of them seem to be like the second picture so I tend to think mine is an early type but I've no proof.

Another subtle difference with the S models is the way the rear mudguard mounts. Like mine with a strap between the shock top bolts and the later ones that mount off a plate from the frame web. 2 different mudguards too.

rivera said:

Any chance to unblock the breather line in the tank?

Click to expand...

Did you check whether the exit "port" to the air filter is free in the first place?

Or is it too much pressure from both hoses to the tank?

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As their source is the same (crankcase pressure) they don't add up linearly. The old breather is timed and the new one has a reed but is actuated through a rather large "dampening device" in the form of the rather small passages from the crank- to the timing case plus the volume of the timing case itself. However in total that is nothing which a proberly working internal breather line in the oil tank couldn't handle.



Tim

Tintin said:

Did you check whether the exit "port" to the air filter is free in the first place?

Click to expand...

Yes I went up there with a stiff wire as DogT suggested. I think I reached the top with no obstacle in the tube.
What "secret device" is in that top hat?
Maybe it is better to let the tube from the reed valve end in a catch can or similar.

Anyway, we´re about to hijack this thread...

I've managed with lights and mirrors to look inside that top hat area and all that tube from the air filter does is go up into that area and end, maybe 1/2" from the top of so. It was my intention to take the top hat off one of the tanks (I think they're brazed on) and solder a U fitting on the tube so less oil could get into it, but it's probably wishful thinking. That was my intention to stop the oil coming out in the air filter. But no matter what's done, oil vapor is going to get into that tube. That's why I put a catch bottle on it.

I don't think we've hijacked it too much, it's still about the oil tanks.

Hi Dave,
These are the pictures.
Ciao
Piero

Piero,
I wonder if someone has modified a tank like mine. I doubt if the factory would make one that vents to the air. Plus the hole in the air filter is blocked? Do you think the factory did that? Can you see the tube inside from the blocked hole in the front that goes into the top hat, is it still there?

I bet that's someone's attempt to keep oil out of the air filter. It would work. How is the hole blocked? A 5/16" bolt will fit in it nicely.

rivera, if that hole in the air cleaner is open into the tank, I see no reason why you should get pressure or vacuum built up in the oil tank?

Any more Norton mysteries?

Hi Dave,
the tank is stock, i have another two same copy mounted on a 1970 S a 1970 Roadster.
But i have one too with only the spigot to the top hat.
All have the breather hole into the air cleaner that comes from top hate spigot (where starts the hose that goes to the engine breather pipe).
I fit into the hole in the air cleaner (with a hole into the filter and perforated cover ) a hose that goes under at the end of the cradle.
Ciao
Piero

I tried venting the hole to under the cradle and it splashed oil all over under side of bike, so I put it into catch bottle.

Hi ,when i first rode my s type replica i was dismayed at the oil leaking from the bottom of the air filter, i have the tank were the engine breather goes into the top hat, and an internal pipe goes into the air filter. the solution for me was to block the internal breather to the air filter and modify a oil tank cap with a union so i could run a pipe to a breather filter via a T piece to a small catch bottle in the left side cover, this works well and after 1000mls all that was in the catch bottle was 15mls of clean water, cheers pete