Cold operating temperature - Kawasaki KLR 650 Forum
2008+ KLR650 Wrenching & Mod Questions For repair, maintaining or modifying discussions related to the newly updated 2008 and beyond, Generation 2 KLR650 Motorcycle.

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post #1 of 65 Old 03-29-2020, 10:07 AM Thread Starter
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Cold operating temperature

I have a 2014 KLR 650, it seems to run too cold all the time. Instead of installing the Thermo-Bob kit, why can't I replace the existing thermostat with one that opens at a higher temperature?
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post #2 of 65 Old 03-29-2020, 10:54 AM
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Why wouldn't you install a Thermobob and be done?
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post #3 of 65 Old 03-29-2020, 11:32 AM
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Originally Posted by glasair View Post
I have a 2014 KLR 650, it seems to run too cold all the time. Instead of installing the Thermo-Bob kit, why can't I replace the existing thermostat with one that opens at a higher temperature?
Or, just let run too cold.

The problem is not the water temperature; it's the oil temperature. Even with a Thermo-Bob, folks that have installed them report oil temperatures that are less than ideal. In my mind, oil temperatures should be around 220 degrees F to burn off accumulated water vapor. The KLR engine oil temperature with our without Thermo-Bob is less than 190 F. Tom has installed thermo-couples at various locations on his bike's engine and can quote you accurate figures.

I think the impetus for creating the Thermo-Bob was to produce more even engine water temperature via a by-pass, similar to automotive cooling systems. Some folks thought that the Thermo-Bob would cure the notorious '08 KLR oil burning problem, but it didn't seem to have much effect. And oil temps are still not as high as they should be even with the Thermo-Bob installed.

Jason

Last edited by Norton 850; 03-29-2020 at 02:02 PM. Reason: correcting grammar mistakes
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post #4 of 65 Old 03-29-2020, 01:04 PM
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Instead of installing the Thermo-Bob kit, why can't I replace the existing thermostat with one that opens at a higher temperature?
glasair, while I see no problem with the temperature parameters chosen by the Kawasaki Heavy Industries engineer, myself . . . I happen to have a high-temperature (same as Thermo-Bob's) thermostat (new, never installed).

I've offered the part on this website, but . . . Thermo-Bob fans ran, screaming, from the room!

I'm likely considered guilty of the crime of, "engine abuse," inflicting the alleged punishments of: Thermal cycling, thermal shock, excessively cold operation, and probably, some too fierce to mention.

If you'd like to experiment with this component, please send me a private message.
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Last edited by Damocles; 03-29-2020 at 01:10 PM.
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post #5 of 65 Old 03-30-2020, 09:07 AM Thread Starter
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Your right, I could and I probably will.
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post #6 of 65 Old 03-30-2020, 09:55 AM
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Not trying to be rude but the question clearly indicates a lack of understanding of how the thermobob works and what exactly it does. Yes the stock thermostat is too cold and using a higher temp stat would help with that but the most important thing that a T bob does is to greatly reduce the delta T between incoming and outgoing coolant in the cylinder. Despite the fact that there is no quantifiable results that can be bandied about, I personally believe that the Thermobob's reduction of the "cold shock" helps reduce bore distortion and oil burning related to it. I'd suggest careful reading of the testing data and then making an informed decision http://watt-man.com/uploads/TB_Testing.pdf

As I've always said, nobody NEEDS to install a Thermobob and you are free to run your KLR in "as-designed" condition and it may even last a long time in that configuration.....but there is ZERO doubt that the thermobob is an improvement that WILL increase longevity....quantifying that increase is impossible however....chould be 5 miles or 50,000....truth is likely in between! ;-)

Dave
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post #7 of 65 Old 03-30-2020, 11:00 AM
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Originally Posted by DPelletier View Post
there is ZERO doubt that the thermobob is an improvement that WILL increase longevity....quantifying that increase is impossible however....

Dave
Gee Dave, I didn't realize you were so passionate about the Thermo-Bob!

Jason
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post #8 of 65 Old 03-30-2020, 11:02 AM
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Quote:
Originally Posted by glasair View Post
I have a 2014 KLR 650, it seems to run too cold all the time. Instead of installing the Thermo-Bob kit, why can't I replace the existing thermostat with one that opens at a higher temperature?
Quote:
Originally Posted by Damocles View Post
glasair, while I see no problem with the temperature parameters chosen by the Kawasaki Heavy Industries engineer, myself . . . I happen to have a high-temperature (same as Thermo-Bob's) thermostat (new, never installed).

I've offered the part on this website, but . . . Thermo-Bob fans ran, screaming, from the room!

I'm likely considered guilty of the crime of, "engine abuse," inflicting the alleged punishments of: Thermal cycling, thermal shock, excessively cold operation, and probably, some too fierce to mention.

If you'd like to experiment with this component, please send me a private message.
The relief hole or air bleed hole in the 90C thermostat is about 3-4 times too small to allow proper operation in the non-bypass standard cooling system.
Too small of vent hole will drasticly Increase the delta T between coolant temps entering the base of the cylinder during the first 10 - 20 minutes of operation of Every start-up cycle, dependant on ambient air temp.
Too large of vent hole will lengthen warm-up time, inspite of being a hotter set point.

If either of you would care to copy the "vent slot" of the oem thermostat into the upper edge of the 90C thermostat it could be used and has been used by a few individuals, but it is still NOT Recommended practice.

Why mess with success? Wattman did all the experimenting for us and invented the Thermo-Bob.

pdwestman
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post #9 of 65 Old 03-30-2020, 12:05 PM
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Gee Dave, I didn't realize you were so passionate about the Thermo-Bob!

Jason


I know you're teasing but...

I had my KLR for 6-7 years before I even heard of a Thermobob.....and once I did, I decided that I don't ride in cold weather and my 2001 had 20,000 kms on it and it's been fine so why bother?.....Then I read some well articulated replies on a thread about 10 years ago that started me questioning my assumptions on the T-Bob. I went back and read everything on Bill's testing as well as general cooling system design and operation.

Based on my research and my background in post secondary physics as well as my experiences as an amature mechanic/automotive restorer and race bike maintainer, I decided that I was wrong and that a Thermobob is a benefit in any ambient operating conditions. I don't think any logical person can conclude that it isn't a positive change to the design of the cooling system; but rather is it "necessary".....IMO, it isn't strictly necessary.....but it's better....how much "better" or what does "better" mean for the life/longevity/operation of a KLR; NOBODY knows for sure and it can never be quantified or proven IMO. In order to quantify the effects you'd need a couple dozen KLR's and monitor them and use them/ride them in exactly the same way until they finally failed....and even then the sample size would probably be too small.

So, at the end of the day, it's a matter of budget, priorities and expectations. For me, I intend to keep my KLR's for a long time and the cost of a T-bob means little to me so it was an easy decision. I fully recognize that others have different metrics and they may conclude it isn't worth it for them. I'm not going to say they're wrong...but I will stake my credibility on the statement that the T Bob equipped KLR cooling system is superior to one without....


2 cents,
Dave
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post #10 of 65 Old 03-30-2020, 01:30 PM Thread Starter
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Ok, I went to the Thermo-Bob site and read their literature and carefully considered the diagram for their bypass system. It appears that for cold weather operation this is a good system, as it continuously circulates warm coolant from the cylinder directly back to the cylinder and bypasses the radiator only allowing enough coolant to flow from the radiator to maintain a specified temperature. However, my concern with this system is operation in the summer when the ambient temperature is over 100 degrees, and the bypass is still diverting hot coolant from the radiator and cycling it back into the cylinder. I would think you would want 100% of the coolant cycling through the radiator for maximum cooling when the system is overheating. Has anyone had a problem with overheating in the summer with this system? The Thermo-Bob site does not talk about hot weather operation.
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