I've attempted to address this issue by placing car door edge rubber over the edge of the fan shroud. This is the stuff which has a soft, pliable side which seals the shroud to the radiator core and so blocks the space between the steel shroud ring and the radiator.
If one does a bit of smoke testing or even uses a ribbon or bit if tissue, one will discover that the fan's action in extracting air from the fan shroud results in a significant amount of air entering between the fan shroud and the radiator. Obviously this reduces the air flow through the radiator core by reducing the low pressure area in the shroud.
It might be well to remind that the fan causes air to flow through the radiator core by reducing the air pressure at the back of the radiator (inside the shroud). Atmospheric pressure forces air to flow through the radiator core into the low pressure area inside the shroud. The fan does not "pull" the air through the radiator.
One cannot do this for the Gen2, obviously, because the fan shroud is integral to the blades.
I'd thought about adding another fan or the possibility of usinrg a "box" system on the back of the radiator such as that used on Volkswagen Rabbits and other cars. This system has an enclosure over the back of the radiator which encloses the complete rear of the radiator so that the fan's action is applied to the whole of the radiator core rather than only to the ring shroud area as for the KLR.
This system was/is common to cars but the difference in the VW system is that there are additional vent holes in the rear of the shroud. Rubber flaps fall over the vents so that the fan's action does not result in air entering into the back of the shroud because the rubber flaps block the vents. When the radiator is moving through the air because the car is in motion, the air pressure in the shroud becomes higher than that behind/outside the shroud so the resulting air pressure inside the shroud opens the flaps and the full air flow through the radiator is unrestricted by the smaller fan outlet hole.
I may take another look at that possibility as it would be fairly simple to make a shroud from Lexan if only for testing. I do lack the precise instrumentation and the expertise to properly evaluate the effects so am trolling to see if Bill Watson might weigh in...?
Any chance you're reading this Wattman?
Perhaps I'll email this thread link and ask if he has time. Nothing better to save wasted effort and to learn that to ask someone who really knows.
Has anybody tried to install a better fan on the existing radiator? I wonder if you could make any gains that way? I guess you couldn't make it much larger, but perhaps one with more efficient blades spinning at a higher rate to draw more air through the radiator at low speeds?
I'm guessing it's not feasible or effective since I've never heard of anybody doing it.