Oil Tank Drain Valves and Plugs

Oil drain valves and plugs

Regular oil changes on Harley-Davidson motorcycles (force feed circular lubrication system from 1936/1937 on) required a drain plug. Of course one could drain the oil tank in a different manner, e.g. with an pump and a piece of tubing. But there's nothing simpler to use than good old gravity. Place a funnel or a PanAm Oil Slide underneath the drain plug, aim it for the PanAm oil change canister, slowly open the drain plug and there you go!

Up to the 1980es Harley-Davidson recommended regular flushing of the oil tank with kerosene. The reason for this was that the then used monograde oil did not have the same ability to keep debris particles floating. Instead this material sank to the oil tank bottom and had to be flushed out from time to time. Just to keep it from re-entering the oil circuit. The kerosene that had taken up the debris was drained through the oil tank plug just in the same manner as the oil.

Magnetic drain plugs

Since motor oil always contains a small amount of metal abrasion, magnetic oil drain plugs have become very popular. Steel flakes, and in the case of more extensive damage, larger splinters, stick to the magnets glued into the screws and sink to the bottom of the oil tank. Modern multigrade oils are very good at keeping metal particles in suspension, and the magnets are relatively weak, so most steel particles are not attracted at all. Aluminum and bronze cannot be magnetized. So if a piston or a plain bearing bush really surrenders, the resulting non-ferrous metal debris would not stick to the drain plug. In the general view, a fine filter is much better.

Drain Valves

Drain valves make it easier to aim into the waste oil container. The next time you change the oil anyway, replace the drain plug by a valve and from then on you just will have to attach the hose-equipped adapter to the valve and you will aim the hot oil spurt directly into the pan without burning your hands. Really a cute piece, such a Stahlbus drain valve.

I have neither a drain plug nor a drain valve on my oil tank. So how the h… do I get the oil out?

Keep calm. And don't run about looking for a pump. Most probably you own a Softail or a Sportster. Since 1986, these models have had something much cooler... If you look closely, you will find a piece of hose under the bike, somewhere in front of the rear wheel, connected to the oil tank but ending blindly. It is normally closed with a plug that is clipped to the frame. This piece of hose is the drain hose. Simply loosen the hose clamp, pull the hose off the plug and aim the engine oil into the tray placed underneath.