I have been riding my klx250sf to summer class the past few days and couldnt help but notice my cooling fan is not turning on. I find this surprising because it was in the high 90's here in pittsburgh. Before I put in a kouba screw and got my jetting pretty good my cooling fan used to always turn on. Yesterday I actually saw it turn on and it seemed really sluggish. It used to blow a lot of air now it seems like a small computer fan.

With the bike off I checked for any rocks or obstructions to the fan that would cause it not to turn but I found nothing.

Do you guys think my bike is running at a good temp and simply doesnt need to kick the fan on or is the sensor or something broken?

Thanks for the help!

 

It's my understanding a lean engine runs much hotter than a properly jetted or rich engine.

 

Borg, I believe you my friend are correct about that! However my concern is that I ran this bike for 45 minutes straight mostly in the 7-8 rpm range and low stop and go traffic while it was almost a 100 degrees outside. I feel like that should be enough to make the fan kick on but it didn't.

If this is simply a result of good jetting then cheers! but I was hoping someone could provide insight as to how I can determine if the fan is broken or if my jetting is just spot on so the fan doesn't need to turn on.

 

Too lean of jetting can blow a hole in your piston.... due to the excess heat.

 

Mines only come on once...after spinning and revving the hell out of my bike trying to get up a very steep, muddy skidder track for 5 minutes...never on the road...the radiators are as big as the one on my EX500...excessively cooled for a 250 not riding hard in the dirt I'm guessing.
You could let it idle for a while and see if it comes on, it should at some point with no air flow. If it doesn't come on in 5-10 minutes, would be worth checking into your temp sensor. If it comes on but doesn't spin fast, that could be a dying fan (never seen that with a motorcycle) or an electrical problem. There my usefulness ends.

 

Get some jumpers and power the fan direct with 12V to see if there is a voltage drop or borderline grounding somewhere causing the "runs slow". It did come on so the sensor seems OK unless it's contacts are somehow contaminated.
Checking the '09 wiring (don't know which year yours is): Black/yellow from the fan goes to ground, fan blue is hot from the fan switch. Fan switch: Blue/black is power to the fan switch from the 10A fan fuse.

 

i have ridden through nevada in the summer time 110+F all off road and never really see the fan kick on if you are moving this bike stays cool the 11:1 comp just doesn't build a lot of heat, but i would run through the wiring just to be sure and just hook your fan up to the batt. and see if it spins up if it doesn't its the fan if it does its someting else in line

 

I had the fan come one once about 5 years ago, it was 100 degrees out, in first gear, on a really hard single track trail, it actually scared me a little since I didn't know what it was at first.

 

I never had the fan on the KLX come on.

I used the killswitch once on my DRZ when it was really hot, and the fan was on... I was surprised, not that loud.

 

I've had my fan come on a couple of times when i was idling for extended periods doing carb adjustments after my big bore install. Never had it come on while moving.