Heiden/Mikes or Hugh hasn't given any data to confirm the so called oil cooler actually cools the oil and reduces the heat overall.
Mikes and Heiden call theirs an oil filter/cooler kit, and State.
"Fits: All 650's 1970-84 Kit is complete with Gaskets, Mounting Hardware and internal housing parts (Not shown) plus a filter element. No mods to install - improved filtration > Improved Cooling = Longer Engine Life.
Heiden/Mikes don't claim it cools the engine or oil as such but their claim is the better filtration coupled with the extra cooling abilities prolong engine life.
looking at Mikes/Heiden unit it has the solid alloy insert so extends the filter into the unit where the cooling fins could do their job. The outer grove is deeper than the inner 2 and goes deep enough to be cooling the face of the unit where the outer end of the filter sits against. There will be a certain amount of oil movement around the outside of the filter between the inside of the unit to cool the oil.
My thinking is, the solid alloy insert the oil surrounds, (before it gets to the external part of the unit), would be as hot as the engine oil and when the oil goes back in the filter and down through the middle of the insert the heat retention of the insert would reheat the oil as it is going back into the engine.
Hugh's handbuilt calls his a "Bolt-On Oil Cooler" and states.
"We have the largest surface area of any Bolt-On oil cooler on the market, while increasing oil capacity by 120cc’s. More oil and more cooling surface = Cooler Running XS650 Engine!"
Hugh claims his is an actual engine oil cooler.
Please correct me if i have missed something.
looking at his unit on his site It looks like the original filter stays in its original place. If that is so how is the oil in the outer part of the unit getting pushed around enough to be effective as a true oil cooler. Oil is directed on to the filter not into the outer part of the unit