[mr. softie]

There is a bit of oil flow from the camshaft galley as the oil lubricates the valve rockers and camshaft and then moves to the sump. The oil that lubricates the cylinder walls also has a cooling effect on the cylinders and piston. I just have a "gut" feeling that if the oil was cooler it may have a small cooling effect on the whole motor. I realize that the GZ motor was not specifically designed to be oil cooled, so the effects might be less than hoped for. I never thought the GZ motor ran all that hot till I saw Patrick_777's pic. I have read by the way that the oil should not be cooled to less than 190 degrees or so, not sure why, flow maybe?

As far as the oil level goes, without an anti back flow valve in the oil cooler supply line you are correct, the oil level in the sump would be way high at start up, which could lead to blown seals, and at the least making it impossible to check oil level. Another complication.

One of the nice things about the GZ being so simple is that it is well designed and very usable in stock form. If it ain't broke don't fix it. This is probably not such a great mod.