KLR650 runs HOT....help?

I have a 1991 KLR650 with almost 9000 miles on it. The bike is in great shape, but gets very hot in a short amount of time. The bike was originally a west coast model (I'm on the east coast) and since new has had some of the pollution control stuff removed. The temp guage doesn't take long to max out whether the bike sits at idle for a while or it's taken for a short ride. I haven't had the bike long and haven't ridden it much. The fan does go on but it doesn't seem to cool the bike much when it is running. I usually resort to shutting the bike off and letting the fan run to cool it down. Are these bikes known to run hot and does anyone have any suggestions? Thank you in advance for any replies.

No idea,I'm on the east coast (Ma.) and mine is coldblooded (and is Ca. emissions which have not yet been removed).

Have you checked the cooling system to ensure you don't have any air in the system?

I have similar problems with a new '05, so I did some searching around a few web sites. Seem they all run "hot". The gauge will be in the upper 3/4 to 7/8 of the scale in slow traffic and/or while stopped. It seems to happen in a very short time too. None seem to go into the red zone though.

I would imagine that your CA emissions stuff adds to this problem.

First off, the general consenses is to ignore it unless it goes into the red. Seems normal. Second, an easy fix is to open the idle mixture screw to about 2.5 turns. There are several other mods directed at air flow that are said to help some. I just did the mixture bit, but haven't ridden it enough yet to give you a report (snow).

Do a subject search at www.klr650.net to see some of the hundreds of plausible and not so plausible "solutions". Meanwhile, unless it is getting into the red, just ride it. Everyone else does!


Iggy, definitely use the KLR board to eliminate any known problems with the cooling system. Ask about jetting, lean jetting also produces excessive heat.

For bike emissions control I have no info, but the 650 board can help you rule out problem components. I would not recommend additive fixes until you get the systems check down, if there is a persistant and chronic heting problem, make sure you run a good coolant like water wetter by redline, engine ice or evans radiator fluid to reduce heat.

In the 'General" discussion they are talking about an oil additive called two2cool.


Anything to do with oil is a firestorm controversy, this product is getting some use by local riders here with good results- see for yourself.

I have the same problem with my klr650 always getting hot in traffic and if i am doing slow dirt riding or rough terrain. I actually just added a second cooling fan, but do have not really tested it yet, see, i have done a lot of electrial additions/modifications, and have a switch to turn off my main headlight, save that 55 watts, and then can turn on this extra fan 70watts or just flip my override switch for my main fan (70w). BEST ADVISE i have been given is not to shut off your engine in traffic or anything, it is much harder on the engine to start with thin hot oil, but to rev the engine a bit to just keep the OIL PRESSURE up. I do this in traffic, and the bike seems to keep around the same temp. later

We have no experience with this specific model. Does anyone know what engine oil temps they are getting??

On many models the oil can exceed the coolant temp as much as 150 degrees. Much of the time it will be atleast 50 degrees hotter even on street bikes.

Generally when a bike is reaching high temps from slow riding/traffic conditions the reason is obvious. The rads arent working as good as they should be since there is no or little air flow.

Much of the time during slow technical trail riding or stop and go traffic you are using the clutch excessively. This only adds to engine temps. Since most coolant pumps are in the oil bath this heat is being transferred to the coolant also.

The only variable with Two2cool is how hot your engine oil is to begin with. We have seen big bore stroker harleys with oil temps exceeding 300f and sport bikes over 250 f in the stop and go traffic down the strip in daytona during bike week. In thse models overheating isnt an issue after adding two2cool. Any questions please feel free to ask. Norman

Maybe a broken water pump impeller shaft ???

I own a 92 and it did the same thing until I re jetted it. You may also want to check the radiator to see if it is plugged up. My KLR is piped and opened up air box and it ran about 3/4 up on the temp until I re jetted it. Now it gets half way up on the gauge in the summer and 1/4 in the winter.

Maybe a broken water pump impeller shaft ???

I do believe we have a winner here!

There is a lot of problems with either a broken shaft or more common, a loose impeller on the shaft.

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