2011 FE390 cooling question

mikej55 · Jun 19, 2013

I installed a fan kit when I first got my bike so it has never really run hot on me, fan just comes on when I get on tight single track. Recently I put new hoses on that are a little bigger and eliminated the thermostat. It seems like now my fan comes on more often and not just when I am on single track. It was pretty hot temperature wise the other day while riding (upper 80's) and that may have contributed to the fan running more but we were not riding much single track mostly just fast fire trails that day. One of the guys riding with me mentioned that the water may be circulating through the system too fast without the thermostat to allow for the motor to be cooled properly. Should I be concerned! I do live in Florida and the temps here while riding are usually between 40 and 90 degs. F. so I am not concerned with it freezing. Should I put the thermostat back in or am I better off without it for cooling purposes! I do have the competition map installed and also an FMF pipe.

kipper · Jun 19, 2013

I have the same config on my 2010 390 and have no problems. My fan only comes on at about 95 I think and takes it down to 90 degrees. As I have no thermostat on the radiator I have a ktm two stroke fan that has an inline thermo switch to turn the fan on/off.

Not sure where your temperature pick up is or if you over it?

DaleEO · Mar 22, 2014

mikej55 said:
I installed a fan kit when I first got my bike so it has never really run hot on me, fan just comes on when I get on tight single track. Recently I put new hoses on that are a little bigger and eliminated the thermostat. It seems like now my fan comes on more often and not just when I am on single track. It was pretty hot temperature wise the other day while riding (upper 80's) and that may have contributed to the fan running more but we were not riding much single track mostly just fast fire trails that day. One of the guys riding with me mentioned that the water may be circulating through the system too fast without the thermostat to allow for the motor to be cooled properly. Should I be concerned! I do live in Florida and the temps here while riding are usually between 40 and 90 degs. F. so I am not concerned with it freezing. Should I put the thermostat back in or am I better off without it for cooling purposes! I do have the competition map installed and also an FMF pipe.

Was looking around for another thread when I came across yours............

The system was designed to have a thermostat in it. The main purpose the way I see it, is to make sure you have at least 185F on the water jacket around the piston. If it is too cool the rings aren't sealing properly. Also, you risk thermal shock. Let's say you are riding single track and everything is hot, and you jump on a dirt road and start moving right along, the coolant is going to cool down very quickly along with the cylinder, and the piston is still hot. So the cylinder shrinks and the piston starts to scuff, or maybe seize. Cold seizures were a huge problem when water cooled bikes first came out.

For you bike to perform as designed it needs a certain amount of heat. Running a motor below its operating temp is going to decrease performance.

If your fan is coming on more often, that means your coolant is hotter right? Or at least to the 100C that the switch senses. If the coolant is flowing too quickly the coolant isn't there long enough to dump the heat.

What kind of coolant are you running?

akshun · Mar 22, 2014

It always amuses me when somebody tells me they removed the thermostat to "help" cool their machine!

2011 FE390 cooling question

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