Re: (Monstaman)
For what it's worth, I've been running an "upside down" (that is, with the fittings on the bottom) oil cooler under the horizontal cylinder all year with no problems. I'll post a pic later, but the cooler was an eBay purchase (I now have 3!) designed for mounting above the cylinder. (I actually like the looks of the cooler in the lower position, and it makes me feel better about airflow to the rear cylinder.)
However, 1) it probably makes no real difference, and 2) like you said, with the pods you have a lot more open area now.
I have had no issues with trapped air, false oil level readings, or anything like that. The fact is, there's a whole bunch of air above the oil in the crankcase, so it's kind of a moot point. At worst, once the engine is running, whatever air there may be in the cooler ends up in the crankcase, which is vented to the atmosphere via the breather in the first place. I don't think you'd be pumping a big air bubble through the oiling system over and over... it's not like the closed-system coolant in a liquid cooled engine, where a traveling air pocket can create hotspots and can cause failure of water pumps, head gaskets, etc. It's also not like a hydraulic system, dependant on lack of air for correct operation. If that earlier post about ideal mounting positions for oil coolers is correct, and a vertical mount with one fitting above the other is good, then you'd still have the same hypothetical oil draining out of the cooler, right?
The only possible downside I can think of is that an oil cooler with the fittings at the top will "fill" with oil, thus exposing more of it to the cooling area between the reservoirs on each side, thereby increasing the actual amount of cooling. With the fittings on the bottom, the oil pump has to pump the oil cooler full of oil, in order to get the level of oil to the top and expose the same amount of oil at any given time to cooling. I'm not sure this happens; it may be that you only get oil across the bottom few runs. Then again, the oil cooler itself could hypothetically be colder in the first place, since there's less hot oil in it, there by increasing the cooling of whatever oil actually makes it through.
I don't think it matters. All I do know is that I have thought about this waaaaay too much myself.
Maybe Shazaam will chime in...
Modified by DesmoBob at 11:31 AM 8/10/2005