Another guy I knew had a 99 CBR900RR and he told me his CBR runs best at about 74 degrees C (165'F). My 1993 runs at a constant 80C (176'F) on hot highway days or slow traffic when my radiator fan is switched on. However when its a cold morning it runs cooler thanks to the cooler air but all what it does is take its time to ket there (like 20 minutes or something) to 176F and stays there. It gets there sooner at highway riding when the revs are high.

How cold was there air when you checked your temp and how long did you ride for? If you have been riding for a long time then I would suggest having a look at your thermostat. If it is faulty you might be riding somewhere thinking your engine is fine while all the while it was red hot.

Nothing to lose by having a checkout,

 

Well, I let it get up to 215 degrees last night while sitting via the gauge. Fans never came on. I don't know if that means the gauge is bad, or the sensor is bad, or what. I'm going to replace the thermostat soon, but I'm still upset the fans didn't come on. 215 I was told was where the engine should be shut off at. I rode out of the parking lot, down the road 1/2 mile and it dropped to 180 degrees in that short distance.

 

Damn man! That is hot! The fan should have definately come on long before that. Try hooking up your fan directly to the battery to see if you fan is shot first. If thats the case then you can simply replace a cheap fan than a expensive sensor. Maybe it could also be the wiring of your fan. Try checking the simplest problems (actual fan and wiring), before messing with the big electronics. If there is enough space to work with, heat up your bike and then check your wires. Maybe there might be a small break in the wire or a misconnection preventing the fan from being switched on.

Sorry I forgot to ask if your fan was working on my previous post

I have a manual switch connected to my fan which I flip on during hot days and leave off on cold days, so I bypass sensor and problems.

 

Well, the gauge is accurate. I let it warm up to 132 degrees, and then popped the radiator open and got splashed a tiny bit, but proceeded to check the temp. I used a laser heat gun, and shot straight down into the radiator for the hottest temperature. I got 117 degrees as highest. I take into account the radiator will be a bit cooler than the lines preceeding it, so i figure that is about right, if not safe. It will get a new thermostat.

As for the fan, I might hardwire as you have. Since I know the gauge and sensor are working, and the fan and thermostat aren't correctly atleast, I will run it a small bit.

 

Wire the fan to a switch so you can control it is the way to go. Who needs a thermostat. Mine runs cool (thanks to engine ice) so not that big a deal but if I ever have problems I'm going manual.

 

on these hot texas days and nights my bike is in the 200's when sitting and 180 on highway. fan does not kick on til 218. its hot. i am thinking about running water or something and i love the idea about the fan. but otherwise the temp is the norm from what i hear about these 98-99.

 

Well, that puts my mind at ease. I'm going to hardwire the fan as mentioned above for piece of mind. Is there a way to put it in-line with the auto-switch as well? That way in case I forget while riding 2 up or something. I do like that it runs cool though, since the engine has some work done to it and I've no idea how it effects the heat production from the engine.

 

You can just run a wire from the hot fan lead to the battery and put the switch on it. that way the original wiring will keep the auto and the switch can manually turn it on. OR You can wire it to a switched hot lead and that way you don't have to worry about leaving the fan on when you turn the bike off.

 

i saw a switch the other day that when it was in the on position it had a light come on at the end of the switch. that would help to see it if someone forgets.

 

where do you live i am in long beach, ca i would let you use my shop manual for 1998. pretty much covers it all