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1994 KLR650 Overheating

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While returning from a late afternoon ride today, I pulled up to a red light then noticed the temp gauge needle went from about half-scale to pretty quickly towards the red zone. Before it got there, I cut through a parking lot to keep airflow through the radiator, got back on the main drag and leaned over to see the radiator--the fan was not spinning, I can turn it with my hand though. Arrgh. :cry:

The good news is that the fan comes on like it always does for a little bit after you turn the bike off. So the shaft is turning the fan still--it's not stripped out and the circuitry it at least partly okay.

But the fan doesn't spin while riding now. The bike has just over 16,200 miles.

I've only put a bit over 200 miles on the bike since I bought it after Thanksgiving.

Any ideas?

Fuses, relay, some circuit board, thermostat, water pump??? Any ideas are appreciated. It looks like it will be a beautiful weekend to ride in Dayton and I don't want to have to be on the sidelines. Hopefully, it will be a fix that I can do.

I am checking the coolant level first thing tomorrow. I just topped off the radiator with motorcycle coolant and distilled water last month.

Here are my questions:

1. If the coolant level is fine, what do I check next?

2. If it needs coolant, what are the most likely places to check for leakage/consumption on the KLR650's. What is that symptomatic of?

3. Do those CD-ROM Service Manuals for the KLR650 worthwhile for troubeshooting, or are they just a bunch of exploded assembly drawings and parts numbers? :cry:

Sorry if this may be elementary to a lot of you, but I want learn how to work on the bike myself without running to the dealer everytime an issue happens. I haven't worked on any bike since '91 and that was just changing the oil and filter and adjusting the chain tension.

Thanks!

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The first thing to do is idle the bike. See if the radiator starts to get warm. If it doesn't, either your thermostat is bad or your pump isn't turning. It's highly unlikely your pump is bad. The most obvious thing would be the thermostat. Get the manuals (KLR600 and the 650 supplement since the 600 is used as a base manual) and check thermostat procedures. The most likely scenario is that your little fan switch is shot. This is a cheap little thermostatic switch in the lower left corner of the radiator. The best way to check it is turn on the igntion (don't start it) and run the lead to ground. If your fan turns on, this switch is bad. When the switch gets hot it pops and grounds the circuit. As I'm thinking about this, do the fan switch test first. It's quick and easy and won't take as long as idling the bike. It's also the weakest point of the system. If this doesn't solve it, post again and let us know. I actually wired a toggle switch between the thermo switch and the fan relay. This way if the thermo switch goes bad, I can use the toggle switch to turn the fan on manually. Don't cut the lead there now and wire the toggle in between, but rather hitch hike another wire separate from the one already there. This will give an alternate circuit to do the same thing (turn the fan on). These are extremely easy bikes to work on, so don't be afraid to dig in. Buy the Kawasaki manuals. The CD's may be good, but unless you have a laptop next to you it's going to be a pain in the ass having to run inside and print out a different section in the middle of your project. http://www.dual-star.com has the manuals, and you may find them cheaper on other sites or ebay. Good luck! :cry:

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You may not have a problem. What was the ambient temperature ? My KLR 650 will go from about mid point to just off red when waiting at the traffic lights when the temperature is typically about 25C. It happens alot when the bike has been working hard say sustained 100KM crusing and then slow work between cars.

Just check that the coolant level is normal. Is the exhaust that hot you have to move your foot of the peg ?

Sincerely,

tom :cry:

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I yanked the thermostat and took it to the dealer to check the open clearance. It was fine. The problen was caused by a combination of low coolant (on the radiator side) and a build-up of corrosion on the connector to the thermocouple switch at the bottom of the radiator.

I'm on the road again! Thanks for your suggestions!

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The first thing to do is idle the bike. See if the radiator starts to get warm. If it doesn't, either your thermostat is bad or your pump isn't turning. It's highly unlikely your pump is bad. The most obvious thing would be the thermostat. Get the manuals (KLR600 and the 650 supplement since the 600 is used as a base manual) and check thermostat procedures. The most likely scenario is that your little fan switch is shot. This is a cheap little thermostatic switch in the lower left corner of the radiator. The best way to check it is turn on the igntion (don't start it) and run the lead to ground. If your fan turns on, this switch is bad. When the switch gets hot it pops and grounds the circuit. As I'm thinking about this, do the fan switch test first. It's quick and easy and won't take as long as idling the bike. It's also the weakest point of the system. If this doesn't solve it, post again and let us know. I actually wired a toggle switch between the thermo switch and the fan relay. This way if the thermo switch goes bad, I can use the toggle switch to turn the fan on manually. Don't cut the lead there now and wire the toggle in between, but rather hitch hike another wire separate from the one already there. This will give an alternate circuit to do the same thing (turn the fan on). These are extremely easy bikes to work on, so don't be afraid to dig in. Buy the Kawasaki manuals. The CD's may be good, but unless you have a laptop next to you it's going to be a pain in the ass having to run inside and print out a different section in the middle of your project. http://www.dual-star.com has the manuals, and you may find them cheaper on other sites or ebay. Good luck! :thumbsup:

I believe you are wrong about the way you test the switch. If you pull the connector off the sensor while the fan is spinning the fan will turn off. When the connector is pulled off the sensor and that connector on the wire is grounded the fan should turn on. The sensor is simply a make/break contact that is regulated by the temperature of the coolant in the engine. You can test the sensor by removing it from the radiator and putting it into a pot of water and heating the water in the pot. Use a thermometor to observe the temperature of the water as it increases. Connect a ohm meter to the sensor (body and contact point) the meter will indicate 0 or no resistance when the switch closes. The first thing to look at is not the fan coming on, look a the thermostat (first suspect). Take it out and put it in a pot or water, apply heat, watch the thermometer. The thermometer should open FULLY (almost 2/3 of an inch) when it reaches 157-180 degrees F (depending on your thermostat). Remember the hot water enters the top of the radiator from the engine. If your thermostat is not working correctly the water will not circulate freely and the engine will go to overheated condition. The bottom of the radiator will feel cool because hardly any water is being circulated. A bad thermostat will cause resistance and overheating. First thing - Thermostat. 10/06/09

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I believe you are wrong about the way you test the switch. If you pull the connector off the sensor while the fan is spinning the fan will turn off. When the connector is pulled off the sensor and that connector on the wire is grounded the fan should turn on. The sensor is simply a make/break contact that is regulated by the temperature of the coolant in the engine. You can test the sensor by removing it from the radiator and putting it into a pot of water and heating the water in the pot. Use a thermometor to observe the temperature of the water as it increases. Connect a ohm meter to the sensor (body and contact point) the meter will indicate 0 or no resistance when the switch closes. The first thing to look at is not the fan coming on, look a the thermostat (first suspect). Take it out and put it in a pot or water, apply heat, watch the thermometer. The thermometer should open FULLY (almost 2/3 of an inch) when it reaches 157-180 degrees F (depending on your thermostat). Remember the hot water enters the top of the radiator from the engine. If your thermostat is not working correctly the water will not circulate freely and the engine will go to overheated condition. The bottom of the radiator will feel cool because hardly any water is being circulated. A bad thermostat will cause resistance and overheating. First thing - Thermostat. 10/06/09

:busted::banana: :banana: :busted: :busted: :banana: :banana:

Correction - I stated that the thermostat should open almost 2/3rds of an inch. This may be incorrect. I've checked two thermostats and found that at 200F the thermostat opens a maximum of about 3/16 of an inch or 3.5 to 4mm. Can another member or members confirm that this is correct?

:busted::D:lol: :lol: :lol: :lol: :lol:

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I just posted in another thread but my clymer manual in front of me says stock stat should start to open at 157-162f and be fully open, 3mm or more at 185f. I put a thermo bob on mine and like the results, especially good for cold weather, it equalizes the temp between the head and cracnkcase, do a google and you can read all the research that went into it, only bad thing is it's about 100$, but well spent:thumbsup:

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I just posted in another thread but my clymer manual in front of me says stock stat should start to open at 157-162f and be fully open, 3mm or more at 185f. I put a thermo bob on mine and like the results, especially good for cold weather, it equalizes the temp between the head and cracnkcase, do a google and you can read all the research that went into it, only bad thing is it's about 100$, but well spent:thumbsup:

Why spend 100 dollars for a housing that holds an automotive thermostat when an original Kawasaki thermostat for the KLR is only at most 40 bucks? And for that housing you still have to purchase a automotive thermostat. That's three times the price of the original Kawasaki KLR thermostat. I took a look at the Thermo Bob that is mentioned above. It is an adapter that will acommodate a automove thermostat. Why overkill your bike with a geegaw? A motorcycle is not a car. I like to keep my bike stock, lean and mean, just as the Kawasaki engineers designed it. :bonk:

Next you will try to sell us a carb screen that will give the rider 100MPG.:bonk:

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The first thing to do is idle the bike. See if the radiator starts to get warm. If it doesn't, either your thermostat is bad or your pump isn't turning. It's highly unlikely your pump is bad. The most obvious thing would be the thermostat. Get the manuals (KLR600 and the 650 supplement since the 600 is used as a base manual) and check thermostat procedures. The most likely scenario is that your little fan switch is shot. This is a cheap little thermostatic switch in the lower left corner of the radiator. The best way to check it is turn on the igntion (don't start it) and run the lead to ground. If your fan turns on, this switch is bad. When the switch gets hot it pops and grounds the circuit. As I'm thinking about this, do the fan switch test first. It's quick and easy and won't take as long as idling the bike. It's also the weakest point of the system. If this doesn't solve it, post again and let us know. I actually wired a toggle switch between the thermo switch and the fan relay. This way if the thermo switch goes bad, I can use the toggle switch to turn the fan on manually. Don't cut the lead there now and wire the toggle in between, but rather hitch hike another wire separate from the one already there. This will give an alternate circuit to do the same thing (turn the fan on). These are extremely easy bikes to work on, so don't be afraid to dig in. Buy the Kawasaki manuals. The CD's may be good, but unless you have a laptop next to you it's going to be a pain in the ass having to run inside and print out a different section in the middle of your project. http://www.dual-star.com has the manuals, and you may find them cheaper on other sites or ebay. Good luck! :bonk:

I replied to this post not long ago marked 10/06/09 I am replying to it again with better information so you ThumperTalker members and guests will no longer have to look all over the web to only find half truths and misleading information.

I stated in the 10/06/09 reply that the switch is a simple make/break contact switch, that information is wrong. It is a resistive diode. More specifically it is a Zener diode.

Pro Marinero is only half right which makes his answer wrong. He says that the thermostatic switch is shot. He calls it a "cheap" switch which in reality is not cheap (about 60 to 70 dollars). The only sure way to test the switch is to drain the radiator and remove the switch. The switch is a electronic switch based on a diode. If you want to learn how a diode works consult a creditable source such as a Encyclopedia in hard copy form. Try The New Columbia Encyclopedia or Encyclopedia Britannica.

Here are two links that I thought explain a diode's characteristics in graphic form:

http://hyperphysics.phy-astr.gsu.edu/hbase/Solids/zener.html

http://www.thermengr.net/TechBrief/TB-02.pdf

You can see the sensor is a diode by its physical appearance but to prove to yourselves that it is a diode test it with a digital or analog ohm meter.

So take the ohm meter and place one lead on the threads of the brass and the other lead on the sensor end that has the connector . Set the meter at 2000k. Observe the reading. It is not important what the reading is for now. If you are using a digital ohm meter there is a negative sign that will appear on your display indicating that the polarity is set wrong. Reverse the leads. You will see the negative sign when you switch polarity. Try it several times. The polarity sign appears and disappears as the leads are changed. If you do not get the polarity change indicator you either have a meter without a polarity indicator or the diode is defective. If you are using an analog meter with a needle pointer then the needle will only deflect when the leads are placed for forward voltage on the diode.

Now take the leads from the ohm meter and simply touch them together. A polarity indicator will not appear. That is because you are simply making and breaking contacts on the leads of the ohm meter. That is how a make break switch works. Either ON or OFF.

The fan switch is not make/break. Rather it relies on the properties of the diode. A diode only allows current to flow in one direction. That is why the polarity indicator appears if the positive and negative leads are connected the wrong way. A negative indicator will not let the meter's current flow through the diode. Reverse the leads and current flows through the diode. You saw that with your ohm meter connected to the switch that it did read resistance. When the temperature of the coolant in the radiator is transferred to the diode, and the temperature of the diode goes up the resistance of the diode lowers until it reaches a point where there is no resistance. It is a gradual downward slope on a graph or it would be like riding your KLR on a gradual downhill slope until you reach a cliff. The cliff is the point of no resistance. That is where the current will flow through the diode energizing the fan.

If the sensor (diode) indicates a reading on the meter then the diode is most likely good. It might be that a thin resistive plating has formed between the threads of the sensor and radiator sensor holder. This occurred with my motorcycle because it sat for eight years. Try cleaning the body of the sensor with some steel wool. Clean the steel wool off and replace the sensor. Then replace the coolant. 50/50 mix. Try it.

I had this problem with my sensor; I would turn off the bike and the fan would shut off after about thirty seconds only to return on again in fifteen seconds. I finally had to unplug the connector to turn the fan off. Turning the key off will not turn off the fan circuit. When the coolant comes down in temperature then the fan will turn off. The circuit is independent of the main key switch.

I cleaned the sensor, replaced it just before writing this post and it works correctly, the coolant is at room temperature and the fan is off. The real test will be when the engine is started and the temperature is reached to turn on the fan, then to turn off the engine and see if the circuit will turn off by itself after the coolant temperature drops and stays off.

Remember if you are performing this test/repair to keep an eye on the temperature gauge. Don't let it get to high. Don't let the engine overheat. If the needle goes to all the way to the right and the fan is not on, turn the bike off before it really overheats and locks up.

The best and most informed KLR riders are ThumperTalk readers and members.

Our paths might cross one day. We will be amongst good company.

Best Always - Middleweight Sam:cheers:

Edited by MiddleweightSam
Sentence construction, wording and the addition of links

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Sorry, the sensor is not a diode device. All diodes will read an apparent resistance when forward biased, and the bias voltage is approximately .7VDC with the exception of Schottkey type devices which bias at lower voltages. The discussion of apparent resistance is quite long,,, so for the practicing mechanic, suffice to say that silicon rectifier devices read about 400 to 700 ohms and zeners read about 1200-1300 ohms when forward biased.

In reverse bias a diode should read infinity with a VOM.

A diode that reads infinity in both directions is "open", a diode that reads continuity in both directions is "shorted".

A diode must read "high" resistance one way and "low" resistance the other way (I'm sure you've seen that in manuals).

If I had a spare I would cut it open to see, but I suspect it is gas operated switch looking at the way it is constructed. (gas heats & expands creating pressure on a diaphragm which closes a microswitch). Actually, that sounds too sophisticated for Kawi.... prolly just a simple bi-metallic. In any case, it is in fact a make/break switch.

EDIT... to correctly evaluate a diode you need to be on a diode function or diode scale on the meter... that will provide the minimum .7VDC to "turn on" the diode. Analog meters have enough juice as is, but modern meters are built to NOT bias unless selected to do so. Auto ranging meters will often find alternate paths... like through your fingers & such... causing funny numbers & twitching +/- signs.

Any reading that will not stabilze is not reliable (beware of capacitors).

Edited by Beezerboy

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