Following the lead of someone who posted that the EX500 fan assembly could be adapted to the KLR650 (forget who this was but please let me know so I can thank the person directly). It does look as though the EX fan with shroud and mounting could be adapted to the KLR but in my case, having an intact fan, motor and shroud, I saw no need to do this.
I removed my stock cooling fan assembly:
You will notice from the photo that I use some automotive door edging to seal between the fan shroud and the radiator core. This is done for two reasons: to prevent air from entering between the radiator and the shroud which reduces the amount of air being drawn through the radiator. This is not a minor effect because the radiator core offers significant restriction to flow so it is easier for air to enter the large gap between the shroud and radiator.
The second reason is to protect the radiator in the event of the shroud or mounting developing a crack. The edging is pulled back to make it more obvious. Find some at a self serve auto wrecker. It's that soft rubber cushion which seals the door to the door frame when door is closed.
I used an old hand held wind speed gauge to try to compare flow as below. You will notice that the EX500's motor is quite a bit smaller as it only draws 3 amps even with the more effective fan.
KLR fan has 6 blades, 5-1/2" diameter fan, 0.925" wide blade, 25 degree angle. 3.7 amps at 12 volts, 25 mph wind.
EX500 8 blade, 5-3/8" diameter, 7/16" wide blade, 55 degree angle, 3 amps @ 12 volts, 28 mph wind.
I next swapped the EX500 fan onto the KLR motor in KLR shroud, 30 mph wind, 4 amp draw.
Fan assembled 14.6 volts, 30 mph+, 5.0 amps tested on bench. Much more total air flow!
With fan installed onto bike with stock wiring, 14.6 volts at battery, 12.8 volts at fan, 4.6 amps. From this one can see that the fan already moves more air but can use help by improving the wiring.
Further testing revealed the following:
Vd in the positive side battery to fan relay white wire 0.310 volts. I soldered a shunt wire from the output of the (previously installed) Main Power Relay to White wire at Fan relay plug.
Vd fan relay Blue wire to fan plug Blue wire 0.385 volts. will deal with that later.
Fan ground circuit Vd 0.48 volts- will deal with that later.
Fan now 5.1 amps with battery at 14.6 volts.
Bent back the fan motor frame sheet metal and steel basket shroud to increase rear opening size. You can see that in the earlier photo. I was tempted to snip the excess sheet metal but decided it would be safer to retain it by bending it out of the air stream.
Much more air flow! There is a real roar under there with much more air flow.
I will improve the wiring between the fan relay and fan motor, as well as the fan motor ground circuit tomorrow but already see a very significant improvement. Likely it is closer to a Gen2's larger fan but may be better, given that one cannot seal the self ducted Gen2 fan to the radiator core.
The EX500's fan blade assembly fits directly to the KLR's motor. The photos I took seemed to have disappeared onto the internet between my camera and computer.
I didn't check to see if the EX500's fan can be purchased separately.
I'm up to 87 modifications on this bike. ;-)