KLR250 running hot.

[rjmartyn]

I bought a KLR250 off a farmer who had used it very little on his property. It is a 94 with only 20000 Kms on it. I got it ready for the road and registered, but now I find that the temp gauge tends to be just about in the red after only a few miles. The LHS radiator was a bit clogged with grass seed etc but cleaning it out hasn't made much of a difference.

The guy who sold it to me said that he replaced the water pump just before I bought it.

Not sure what to do next. I suppose I should flush out the cooling system and I suppose there is a thermostat somewhere I can check out. Any suggestions/comments will be very welcome.

[SSMSCHULZ]

I know it sounds expensive, but a new aftermarket radiator will probably do the trick.  I replaced my stock CRF radiators with aftermarket and I am running 20 degrees cooler.  They are also much stronger if you go down - which I do a lot. Just my $.02.

[crpt]

Don't think it's a good idea to start getting new material. i.e. spending money, before understand what's wrong.  
First things, first.
1 - Does the liquid flow? Remove the radiator cap and verify. (be carefull if it's hot - relief pressure first)  
2 - That thermostat is working or not? Remove and verify (might use hot water or more simple hair drier, hot gun...whatever is at hand). Tooth brush and detergent makes wonders cleaning them.  
3 - Did you really flush the system or just sprinkled some water on it?  
4 - Are those hoses connected the right way?  
5 - Verify fan and switch (radiator)
6 - Verify (clean) temperature sender unit. Next to the spark plug, before the  thermostat. (Tooth brush again  )
Finally get new clean liquid, and make sure there are no air in the system.

Most probably theres enough "gunk" in the system to fill one bucket  

Maybe this can help


Look for more photos with the right sequence for those hoses. Google
Bellow water pump cover, theres a draining screw... Drain the system, remove covers, and go from there...

[rjmartyn]

Thanks for the excellent reply, I found the problem. The previous owner had replaced the water pump and put the radiator pipes back the wrong way around.

[TrailRider]

I LOVE IT when such positive outcomes are reported!

Otherwise, MAKE SURE YOUR BURP YOUR SYSTEM (run with raidiator cap off 'til thermostat opens and coolant circulates; then, top off radator and fill reservoir to FULL line).

Air pocket in cooling system can inhibit coolant flow at low rpm, resulting in high temperature resistered from temperature sending unit in cylinder head, but insufficiently high temperature at thermal switch (bottom right of radiator) to turn on fan.  Result:  Normal cooling at speed, high temperature at idle without fan actuation.

[seabee12333]

Thanks for the excellent reply, I found the problem. The previous owner had replaced the water pump and put the radiator pipes back the wrong way around.

Is this picture the right or wrong hose arrangement?

[rjmartyn]

Wrong arrangement. If you look at "Show us your 250" there are photos there of bikes with the pipes the other way around. The lower outlet has CYL written beside it. But the pipe in my photo goes up to the radiator not the cylinder.

[crpt]

Hi, it's amazing so many of us switch those hoses and never realize it till it starts to overheat.
The funny part, is like you said, it's written in the pump cover.

Note to Kawasaki start using color coded hoses and inlets...


For some reason I wrote item #4 in BOLD 

[rjmartyn]

I think I'll sell this one and get an aircooled bike. 

I thought I'd solved the problem when I found the pipes around the wrong way but in actual fact it didn't really make much difference.  I put the bike aside for a couple of months, but got keen again a week or so ago.

I checked the thermostat, not there, only the outer casing. (must have been removed previously) I've drained and refilled the coolant several times. Got rid of all the grass seed in the radiator. I haven't checked the temperature sensor, but it seems to working OK.

To be honest it has me beat. I'd say that the previous owner had the same problem and he also gave up and off loaded it. He had  replaced the waterpump just before I got it so he must have been having problems with temperature.

I went on a ride today with a group, all had more powerful bikes than the KLR so I had to really cane it to keep up. It spent the whole day either just above or in the red section of the gauge. I had to give up and go home early.

A bike like this should be capable of sitting on 100kph on a paved road without overheating, and the bike isn't much use to me if it can't do that.

[BakonMoto]

...

I checked the thermostat, not there, only the outer casing. (must have been removed previously)...

You may want to try running it with a new thermostat in place. I know that in some (many?) car engines, the thermostat acts as a pressure (or maybe more correctly, a volume) regulator so that the coolant can maintain a certain "residence time" to allow more heat transfer in portions of the water galleries that needed more cooling.

Racers would run without thermostats installed because they didn't want to risk the 'stat closing down during a race, plus they didn't need the 'stat function, since they'd warm up the engine prior to the green flag. However, they would typically install a blanking plate with correctly sized orifices to pass the coolant at the correct rate.

In the case of the KLR250 though, I certainly stand to be corrected.

Bryan

[truck6driver]

...

I checked the thermostat, not there, only the outer casing. (must have been removed previously)...

You may want to try running it with a new thermostat in place. I know that in some (many?) car engines, the thermostat acts as a pressure (or maybe more correctly, a volume) regulator so that the coolant can maintain a certain "residence time" to allow more heat transfer in portions of the water galleries that needed more cooling.

Racers would run without thermostats installed because they didn't want to risk the 'stat closing down during a race, plus they didn't need the 'stat function, since they'd warm up the engine prior to the green flag. However, they would typically install a blanking plate with correctly sized orifices to pass the coolant at the correct rate.

In the case of the KLR250 though, I certainly stand to be corrected.

Bryan

What Bryan said. Running without a thermostat can be worse than having a bad one.
Put one in and try again.

Ray