Heat, Radiator Fan Switch?

Hi All, read lots of threads on the heat issue and possible fixes. (my ST is a scorcher and I almost never hear the fan come on) One mod that I haven't heard yet is to put a switch on the bike, where you could manually turn on (override the thermostat switch) for the radiator fan when you want to, and/or install a bigger fan. I realize the other mods, proper riding gear etc would help, but I was curious about this particular question. Reason being, I had a friend riding Deals Gap with me last weekend and he had a heavily modded GSXR 600 where he had installed bigger fans and a switch that he turned on at low speeds and stop lights. He said the bike was unbearably hot before, but now, he can keep the bike much cooler, proof of which is that his engine temp gauge on his bike actually gives degrees, not bars like the ST. Any thoughts?
2. I've read some threads on replacing the stock thermostat with an aftermarket one, is that set to a lower temp? Would the lower setting thermostat and manual fan keep the engine cooler, resulting in less heat being generated in the first place? I realize that even that heat has to be vented somehow, so the other mods are still viable, just asking.

If your bike holds three bars on the temp gauge it is running at the proper coolant temperature. Unless the bike is idling for extended periods the fans just don't come on very much. If the gauge reads 1 or 2 bars the ECU gives the engine a much richer mixture and gas mileage plummets. It might feel cooler though.

Not sure if running the fans more at a stop would make it feel cooler, or just blow more hot air onto your legs. Would be easy enough to try, though.

want to run cooler take the thermostat out , will run real cool, fan will come on when you idle it for a a bit if you stop after you ride it for a while, ill even leave the key on for a bit to let the fan run when the motor is not running to take some of the heat out .

The only problem with that idea is when you get on a long high speed run the water will run through the engine too fast to absorb the heat, the engine will overheat and WILL NOT cool back down until you put some cold water on the radiator. This is why race cars don't run thermostats, They run water restricters which are nothing more than a SS washer with the proper sized hole.

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Sorry Mike, the laws of thermodynamics are not interrupted by the presence or absence of a thermostat. If the coolant [water] remains liquid, it still absorbs and carries away the heat--the faster it flows, the more heat it can remove.

Perhaps the issue you mention is one of boiling--in the case of too slow or stalled fluid [water], it boils and due to physical properties of the gas [steam], it does carry less heat away, deepening the problem. But to get to that to occur, the system either lost pressure and the fluid turns into gas or did not flow enough. Too little flow, not too much (such as too small of a SS washer or too much radiator area covered).

The only problem with that idea is when you get on a long high speed run the water will run through the engine too fast to absorb the heat, the engine will overheat and WILL NOT cool back down until you put some cold water on the radiator. This is why race cars don't run thermostats, They run water restricters which are nothing more than a SS washer with the proper sized hole.

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As what was explained to me some time ago, the problem is that without a thermostat, the coolant passes through the radiator to fast and does not transfer the heat well. You then have hot water returning to the block where it picks up additonal heat that it can't get rid of in the radiator. It all becomes a cycle until the engine gets so hot that things start breaking.

The problem I see with running a manual switch is this. Have you read any of the posts about people with a failed thermostat in cold temps. In this situation the bike never makes 3 bars. Well in this case their MPG goes in the tank. Will it hurt anything? Not the engine but it will hurt the pocket book when it comes to gas expenses.

Going with what the OP said. The guy that mentioned this idea wasn't running a stop GSXR but rather one that was highly modified. Well being it was highly modified, it may have been getting hotter based on the modifications. Now manually running the fans help cool the bike but down to what? Normal temps that the bike would see if unmodified? I don't know. While this is something that could be done easy enough, I don't think it will resolve the issue but only introduce new issues. That is my speculation based on what we see when the thermostat fails. By the way it fails open so removing the thermostat wont help the issue.

If this were a non-FI bike like the 1100 I would say you have a better chance of success. There are lots of people with manual switches to the fans on the 1100. I just don't see it being a help on the 1300. Now if you fans don't kick in that may be a sign to an issue but mine kick in here in MN so I would imagine they will kick in down in FL.

The guys on the hot rod crotch rockets seem to run fan switches.....they turn them on in town....
Makes sense to me....

I don't think anyone's tried it but it gets pretty darn hot when the fans kick on in a traffic snarl.

iirc the t-stat is c. 180? and so is the aftermarket one and keeps the engine where the ECM want's it.

Proper gear helps and some have reported a noticeabal difference drilling out or removing the inner fairings.

My temp sensor failed and I didn't know the fan wasn't working until I noticed the temp gauge climbing. I installed a simple switch to turn the fan on manually. Just tap into the wire that goes to the temp sensor (lower left side of radiator), through a switch, and then to ground.
I would like to have a light that shows when the fan is on. I'm not sure how to since there is no relay. (the temp sensor switch is on the ground side of the fan) Any ideas on that?

J. Hawkins said:

My temp sensor failed and I didn't know the fan wasn't working until I noticed the temp gauge climbing.

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Things on the 1300 work differently than the 1100. The fans are under the control of the ECM, which reads the coolant temperature sensor and decides when they should be run. If the temperature sensor fails, the ECM will squawk about it.

--Mark

doerbird02 said:

Hi All, read lots of threads on the heat issue and possible fixes. (my ST is a scorcher and I almost never hear the fan come on) One mod that I haven't heard yet is to put a switch on the bike, where you could manually turn on (override the thermostat switch) for the radiator fan when you want to, and/or install a bigger fan. I realize the other mods, proper riding gear etc would help, but I was curious about this particular question. Reason being, I had a friend riding Deals Gap with me last weekend and he had a heavily modded GSXR 600 where he had installed bigger fans and a switch that he turned on at low speeds and stop lights. He said the bike was unbearably hot before, but now, he can keep the bike much cooler, proof of which is that his engine temp gauge on his bike actually gives degrees, not bars like the ST. Any thoughts?
2. I've read some threads on replacing the stock thermostat with an aftermarket one, is that set to a lower temp? Would the lower setting thermostat and manual fan keep the engine cooler, resulting in less heat being generated in the first place? I realize that even that heat has to be vented somehow, so the other mods are still viable, just asking.

Click to expand...

many of us sport bike guys put switches on because we read it in a forum and therefore believe it must work
as a mechanic i still have know idea why ? My modified ZX12R has seen the heat of death valley and ran quiet well :
on a recent 3300KM on my 05 ST in May to northern British Columbia I found the heat to completely ridiculous even at near freezing I could feel the heat. So after some thermal imaging I did two things. Removed the cats and insulated the bottom of the tank with "not cheap" heat insulator, and after another 4000KM I can say it is not a problem any more, far less than the ZX12R

on the thermostat concept ... this bike is closed loop FI so messing with its operating temp means you may open the loop causeing it to burn more fuel or run crappy