Back from a 50 mile off road trip, included sand and there it was, a spinning fan! I can now confirm it works, when needed, and that's not very often.
Someone mentioned being able to hear it whenever it turns on, this is true.

 

Mine comes on, with the 351, on the trails. Temps here are much hotter than normal, and the fan comes on fairly regularly. Hard to tell it's on, tho, it's so quiet

 

I also added a manual switch to provide an additional option in certain situations. I have a Trail Tech Vapor instrument panel which has a very accurate digital temp gauge. I usually hit the fan button in certain situations when the temp crosses 200 degrees. I've noticed on a long, hard climb on a trail where you're wailing on the bike, for example, that heat soaking is harder to overcome when you wait for the fan temp to kick the fan in. I don't think you're going to encounter engine damage relying the high temp fan switch, but I like keeping temps controlled at a slightly lower point...just my preference.

On the discussion about hearing the fan, I can always feel the effects of the fan blowing hot air on my right leg, even through riding pants. The cooling system on the KLX is very effective. Thank you, Kawasaki.

 

Thanks for this thread. While adjusting my mixture screw today at idle in 88deg temps, my temp light came on but no fan. After reading this post, I inspected my fan closer to find a very slight bend in the mount causing the bottom of the fan to be slightly press against the radiator. A slight adjustment freed than fan which I anticipate will do the trick!

 

While adjusting the mix screw again today, temp light came on just as I was about to take a quick test ride. No fan?

 

I had (hope it's fixed) the same problem, temp light came on before the fan... I replaced the fan sensor, thermostat and coolant (with moto cool), and now it operates normally, fan comes on, and light never comes on..

 

The fan has not been operating at all, found a blown fuse for the coolant fan. Hopefully this will remedy situation time will tell.

Tested fan, comes on intermittently removing hot air effectively. Temperature light did not come on at all after lengthy idle. Problem solved.