Water Temp Rising high at traffic lights

**FEINT** · 13th March 2005, 17:10

I have a 94 CBR250RR and if I sit at the lights too long the water temp rises to nearly "HIGH". Do you all encounter this problem?

I am assuming that this is a common problem on bikes and the solution is to put a fan in?

Anybody here done an installation of the fan and wiring? Any ideas on size of fan and where to get one?

Thanks.

**John** · 13th March 2005, 17:14

There should be a fan on your bike.. check behind the radiator.

**FEINT** · 13th March 2005, 17:25

there is a small fan on one side of the radiator, I just had a look. I don't know if it is working, I will have to check. The wiring for the fan would be just to the battery and back wouldn't it? Is it connected to a thermostat?

Thanks for your reply john. :spudwave:

**saiko** · 13th March 2005, 17:47

Yup, so it gives a reading. You should be able to hear the fan come on. If you park up when it's hot, you should hear it running. If not, I'd check your fuses, & make sure the wiring connector is properly seated. Wouldn't like to run a bike too hot for too long.

Maybe when cool also check the radiator level, it may have overflowed when hot, & a low level could be causing the overheating.

**John** · 13th March 2005, 21:18

There is a way to check that the thermostat is functioning correctly if you checked the wiring and are still abit concerned.

Take out the thermstat, and hang it in a pot of boiling water (with a thermometer in the pot), measure the resistance on a multimeter and if it changes around 90-100 deg then everything is ok, also might be an idea to change the radiator fluid and put a new clean mix in, It lowered my temperatures considerably, but make sure you get all the air bubbles out !

**John** · 13th March 2005, 21:19

oh I forgot to mention the thermastat should be on the left hand side of the radiator, shrouded in thermal tape with two wires comming off it.

**FEINT** · 13th March 2005, 22:08

I checked the radiator fluids and it isn't low. When I am in the traffic jam (I know you all would filter) and I am there for a while and not moving, the temperature gauge will slowly start to creep up. The minute I start moving, and there is air flowing through the radiator, the temperature will start to fall. I have not heard the fan come on at all so far.

Wiring on the bike is pretty complicated, as there isn't a designated fuse box. I don't quite know why the fan isn't coming on.

Here is a photo of the fan and where I think the fuse box is.

I will probably just send it to a mechanic and ask him to check up on it when I send the bike for its service.

Thanks alot for the help.

**F5 Dave** · 14th March 2005, 09:42

Slight misconception: The thermostat is the mechanical device in the water that opens up to let water flow when the bike gets to operating temp & closes when it is below.

The 2 bolt like items in the radiator with wires coming off are 1: the thermistor which is connected to the temp gauge & 2: a thermal switch which turns the fan on. If you unplugged this one (the bigger of the 2) & bridged it (with the key on), then it should start the fan. Possible the switch grounds instead, but if there are 2 wires it bridges. These 2 bolts will live in the front side of the radiator other side of the fan out of view.

Doubt you have a problem, would be a good idea to replace the rad coolant every year to keep it uncontaminated.

**JohnBoy** · 14th March 2005, 10:18

i had an old 89 cbr250r once and it always got really warm after coming off the m'way into the city. i haven't heard of a 4cyl 250 that dosen't, however do a small experiment just to make sure that the fan works.
all you need to do is just to let it run on the driveway until it is a operating temp then afer that the fan should kick in as it gets too hot.
happy motoring

**scroter** · 14th March 2005, 11:18

my old TL had digital temp guage ran normally about 75-80C the fan didnt kick in till about 105C caused by a lot of real slow running, first gear finger operating the clutch stuff, in fact not long after the fan kicked in the clutch packed up and i had to stop and let it cool down. on my current 600 i dont even have the fan i just make sure i dont stop long enough to let the temp get up.

**FlyingDutchMan** · 14th March 2005, 12:00

They're pretty solid bikes... I ran my bike while it was boiling (past the red line) for more than 80km once (The RR has less cooling fluid than the R so be careful!). It also boiled again on the way Akaroa a week ago. Me thinks I'll have to give the whole system a clean. But anyway, 3/4 up the temp gauge is fine, and thats about where the fan should kick in. If its at the end of the white line, thats when attention needs to be paid. Try filling the radiator when its cold and idling, as there might be air bubbles trapped in there which will come out when running.

**bugjuice** · 14th March 2005, 12:11

My CBR250RR had a problem where the loom had been previously attacked and some bits weren't working, one of them being the fan. I just over-rode the main loom and wired a switch so I could control it. When I was in traffic and the heat goes up, I flicked it on, when I was out of it, I flicked it off again..

Next time you see it cooking up, pull over and see if you can see the fan spinning. CBRs were never good at keeping cool. Als, check the radiator has decent water in it, that it's not brown or clear, or anything else but bright green.. If it is, flush it and refill it. And also check the fuses like's been said too..

I don't mind if you pop round and I can help you out if you like, won't take long, as long as it's not a big problem, then who knows.. You came round to the meet about the leathers, didn't you? PM me and we can catch up again if you want.. I'm free most of this week except tonight..

**ghost** · 14th March 2005, 13:30

Get yourself a rocker or toggle switch of suitable amperage, mounted in a suitable location, wire it to close the thermistor connections when on, and in around town/slow riding conditions you can manually turn on the fans to keep eveything at a cooler riding temp.

**F5 Dave** · 14th March 2005, 13:55

If you wire it to close the thermistor the temp gauge will shoot to full temp. Best to wire it to open the thermistor, then the temp gauge will drop to zero so you can stop worrying. Ignorance is bliss as they say.

The thermal switch you mean to say. Could be you can find one that cuts in earlier in an auto electrician supply shop. Surprised that this doesn’t occur std seeing as the bike’s natural environment is a stinkin’ hot gridlocked Tokyo.

Personally I took the fans off my 750 to save 3/4kg. But in doing this I never ride in traffic on this bike.