Oil Cooler

kommando said:

The colder the oil the higher the water content as less water is driven off. High water content ages the oil via oxidation and reduces the oils potential oil film thickness.

Click to expand...

We are in luck having motors with "hot heads" then. The amount of oil going up there (25-40% of the oil circulating at any time) should ensure the water content stays at an acceptable level. Oxidation of oil occurs primarily in the presence of air (oxygen) and heat, so will happen to any of our engines. Debating this topic any further requires hard facts. Oil analysis, anyone?

- Knut

On my Trident at the end of the riding season I do oil drain and remove the oil tank and wash it out. There is always a tiny rust area at the bottom of the tank seam where water sinks down to. Good reason to not have a seam down there eh? Good reason to wash out the tank.
Note: Tridents came stock with a oil cooler with no thermostat.

Measuring the temps around the engine these days is pretty simple, the hottest parts are the area around the plugs and the tappet tunnel which some may find surprising, and thus why I have said it is best to have decent supply of oil to pass over the tappets to remove the heat. Even on one of the hottest days here in the UK, the best I measured at the oil tank is low to mid 80's Centigrade. I choose the oil tank as this is a constant - no ones modifies the oil tank and it does not wear, unlike engine parts that maybe tighter or loose depending on wear. Once fully up to temperature the oil tank will reflect what is happening in the engine providing the oil systems is working correctly, if the oil in tank gets very hot then you can safely say the oil in the engine is having a hard time.
Sadly, the human body is not much help when burning your legs against the oil filled tubes, if could be anything from 50 - 100 C your body just knows that it is hot.

Onder said:

On my Trident at the end of the riding season I do oil drain and remove the oil tank and wash it out. There is always a tiny rust area at the bottom of the tank seam where water sinks down to. Good reason to not have a seam down there eh? Good reason to wash out the tank.
Note: Tridents came stock with a oil cooler with no thermostat.

Click to expand...

Wash and Clean with soapy water and dry it good , and put some rust converter on it .

Phosphoric acid.

Do heads sitting on top of composite gaskets get hotter that those on copper versions?

mdt-son said:

We are in luck having motors with "hot heads" then. The amount of oil going up there (25-40% of the oil circulating at any time) should ensure the water content stays at an acceptable level. Oxidation of oil occurs primarily in the presence of air (oxygen) and heat, so will happen to any of our engines. Debating this topic any further requires hard facts. Oil analysis, anyone?

- Knut

Click to expand...

Search.

I've posted my oil analysis here for years.

concours said:

Search.

I've posted my oil analysis here for years.

Click to expand...

I found two reports taken at 3000 miles after an oil change (mileage of bike around 35 000 miles). Zero water content recorded, which surprises me.

- Knut

Onder said:

There is always a tiny rust area at the bottom of the tank seam where water sinks down to.

Click to expand...

Please note that water by itself doesn't cause corrosion. Water is a transport medium only. The corrosion process requires the presence of a "mud layer" where iron iones are formed, and a depolarizer acting at the Catode somewhere else, but usually close by. Examples of depolarizers are free oxygen, acids, and cations of less active metals. There are always acids forming from combustion blowby products as well as oxidation of hydrocarbon chains. Here, I suspect acids to be the main culprit, but free Oxygen will contribute also. Oxygen becomes more reactive in the presence of acids.
In saline waters, the main depolarizers are oxygen and sour acids such as carbon dioxide and nitric acids.
The corrosion rate can be 10x higher in saline water vs. fresh water.

Your rust problem can be attacked by
* a protective layer (paint),
* removing the Cathode (another exposed spot higher up in your tank),
* passivation of the surface (by exposing the steel to Phosphoric acid),
* replacing the corrosion-prone steel by a stainless steel, such as Inconel,
* providing a sacrificial anode made of Zink or Magnesium.

- Knut

mdt-son said:

.. "hot heads" .. The amount of oil going up there (25-40% of the oil circulating at any time)..

Click to expand...

Where did you get that from ?

There has been research published that motorcycle oil measured at the tank needs to reach a temperature of at least 180f(82C) to burn off moisture and associated contaminants.

I don't doubt and have no way to confirm or deny any of the water discussion. However, the oil tank and feed to the pump are the coolest parts of the oil system and I assume that the oil draining down through the pushrod tunnel is the hottest.

Since it appears that most agree that the Commando oil tank temperature is about 80C and water boils at 100C, then the oil tank has nothing to do with the discussion. Any report that uses the oil tank temperature would have to provide a LOT more info (make, model, ambient temperature, speed while testing, etc.)

Also, since a Commando oil feed to the pump is way above the bottom of the tank, there is a lot of oil that barely, if ever, circulates. This is very different from a Triumph where the feed is from the bottom of the tank and almost all of it circulates.