My fan on my bike seems to run constantly after the bike warms up. I know on my bruin the fan next to never came on. Didn't know if this was normal or something i should take and have warranty work done on.

 

I don't have a 650 but it doesn't sound normal to me. It could be something as simple as a sensor, or maybe the wire came disconnected from the sensor.
I would at least contact the dealer and ask.

 

My 05 V2 has done that since day one. Once the fan kicks on during a ride (assuming summer temperatures), it usually doesn't quit unless I go through some water or until I shut the bike down. It usually takes about 1 1/2 minute for the fan to quit after I shut down the motor. Last summer, after doing some mudding, the fan was staying on almost 3 minutes after shutting down, so I finally pulled the fan off and found quite a bit of mud in the radiator that was being trapped by the fan shroud. A good cleaning of the radiator got it back to "normal".
Although the fan runs almost all the time, I have never had a problem with overheating, so I have never worried about it. I have also read a number of posts saying the same thing, that the fan runs a lot but the bike never overheats, so I assume for some bikes it's normal. Just make sure that your radiator is clean. Also, some people use different coolants other than AC's, and report that it does seem to help it run cooler.

 

I have read a couple of times about the 650's running a little hot, didn't realize that the fan ran so much. I don't understand it. The 650's have lower compression than the 500's and the 500's have lower compression than the 400's and with my 400 the fan may come on once or twice a year for a minute or so.

Do you suppose AC didn't make the radiator big enough?

Here is a thought, (I thought about doing it with my 400 air/oil cooled), a car transmission cooler placed inline with the regular radiator for extra cooling. You could basically mount it anyplace even out back of the machine in place of the useless storage box (just a matter of rounting some hoses). I believe if I had a 650, or for that matter any engine, and the fan ran that much I would be 'jerry-rigging' a car transmission cooler or something. Probably get them all day long at a junk yard for only a few bucks.

 

I have wondered why on some bikes the fan runs so much, but I'm just not sure. I do think on the AC's the airflow may be a little restricted do to the plastic splash guards and by the winch location. Also, it may be partly the Kawi motor. It seems I've read about some of the Kawasaki guys having some overheating at times. The radiator being a little small is also possible. Could the temp sensors vary to some degree? But regardless, as long as the motor doesn't actually overheat, I can live with the fan running a lot.
Thanks for the suggestion.

 

Depending how I ride, my fan can run a lot. If I'm in thick woods with lots of start/stops then it usually runs pretty steady. Just make sure that your radiator is clean and you will be fine.

 

Try and change your coolant. My brother and i both experienced that problem so we talked to the dealer and they told us to change our coolant to a better one. I believe it's called liquid ice and the hot/cold temps are much better than the stock coolant. Our bikes run fine, we got 750's.