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Discussion Starter #1
I'm lining up my mods to my new KLR.

Skid plate, barkbusters, heated grips and crash bars either installed or will be shortly.

I replaced the subframe bolts and added IMS foot pegs today.

Upper and lower KLR Dash should arrive this week.

A low profile drain plug will be installed and doohickey upgrade performed at the 600 mile oil change.

That leaves me with the therm-a-bob mod left as the last big item to check off my list. It would make sense to do it at the same time as the doohickey fix.

Anyway, I understand why a low delta T reduces thermal stress and therefore promotes longer engine life.

However, it also increases the engine's hot leg temperature from 165 to 195F. What's the upper limit for a safe operating temperature for this engine? It seems to me that you're trading one set of thermal stresses for another.

Am I wrong?
 

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Although Kawasaki chose not to put the actual temp readings in their temp gauge, some other guys have figured it out. The redline is 270 (F). It starts tracking temp at 150, then the three quartile points are 180>210>240. These are, of course, coolant temperatures. Not exactly sure what hot leg temperature is. Also, I believe the 165 (F) and 195 (F) are the factory and therm-o-bob thermostat ratings, respectively.
 

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While the Thermo-Bob performs as advertised (stabilizes the coolant more thoroughly and operates at a higher temperature than the stock cooling system), I'm aware of no empirical data quantifying increased service life/improved performance/enhanced reliability from these parameter changes. I know of no component failures traceable to, "thermal shock" from the OEM cooling system operation.

Conversely, I know of no operational down-side to Thermo-Bob installation.

The device is well-made, extensively tested, and marketed responsibly.

In the end, I think the Thermo-Bob decision is one of individual preference and inference; your bike, your choice!
 

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Short answer is twofold; a 195 thermostat doesn't necessarily increase operating temperature (the stock one can open at 165 if it likes, but the coolant can and does get as lot warmer than that) and secondly 195 degrees is around optimal.

The thermobob doesn't decrease maximum engine temp, it increases the minimum temp and reduces thermal shock. As Damocles has pointed out, nobody knows or can tell you that your engine will last X miles longer with a T Bob but logic suggests it can only help.

Dave
 

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Discussion Starter #5
Along the same lines, has anyone researched how a Thermo-bob will affect fuel efficiency or emissions?

Lower octane fuels, which our bikes utilize, burn slower. Does altering the engine temperature have some, perhaps even slight, effect on combustion one way or the other? Would you need to switch to a higher octane fuel to prevent detonation or other associated problems?

I haven't seen this interrelationship discussed so I'm only guessing.

Again, I like the idea of a lower delta between inlet and outlet temps. I even think it's a well developed system, so I'm not trying to detract from the product. I'm simply interested in the relationship between thermodynamic changes and non metallurgical functions and thought this might be an interesting discussion.
 

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Some claim greater fuel mileage with the device, don't know of any such claims by the vendor.

Otherwise, since absolute cooling capacity remains essentially the same, with or without the Thermo-bob, don't think octane considerations arise. After the thermostat opens, same-o, same-o, regarding engine cooling processes and devices (i.e., water pump, coolant, radiator, fan).

I'd think the higher-threshold thermostat would result in a higher nominal operating temperature average, but within the existing range of octane/spark timing/compression ratio considerations regarding detonation tendency.
 

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In theory, proper and stable operating temperatures would be beneficial to both economy and emissions.....but I doubt it makes a big enough difference to be measurable. ....and I'd say no difference on the octane question as well.

Dave
 

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Every KLR should have one no matter the climate in which it lives. Consistent operating temp is the life of any ICE.
 

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This is a new topic to me. I agree with Fox Fader about consistent temps, especially on a carbureted engine. Even though I doubt the the carb body/ intact tract temps very much with or without a thermobob.

However, all engine cooling transpires solely to save the oil. Sure, clearances move around with temps, but the oil is the most fragile thing in your engine. 300-400°F wouldn't phase any piece of metal your engine, but 275°+ starts spelling trouble for your oil real quick.

All that to say this: what effect does it have on oil temps?
 

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I see consistently hotter oil temps= not good in my mind.

Thanks for the link! I'll cough twice and pass on this one. Jmo
 

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Consistent operating temp is the life of any ICE.
WITHIN LIMITS, perhaps quite so.

Only a question: Any evidence of any KLR650 component failure or engine malfunction traceable to, "thermal shock," or heat cycling with the stock KLR650 cooling system?

If so, which components/malfunctions, and their conditions of failure/occurrence?
 

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I see consistently hotter oil temps= not good in my mind.

Thanks for the link! I'll cough twice and pass on this one. Jmo
shinyribs,
IMO, your engine oil should be as warm as your coolant. Wattman of "Thermo-Bob" fame tends to believe the same. The KLR650 engine is one giant Aluminum Radiator. It wants to 'over-cool' every part of it's self!

Check out my oil analysis thread,
http://www.klrforum.com/klr-other-motorcycle-related-discussion/38962-laboratory-oil-analysis-thread.html

And maybe a "little more",
http://www.klrforum.com/1987-2007-wrenching-mods/48377-pdw-oil-flow-mods-order-importance.html
Click on the "Blue links" and enjoy the reading.
There are some pics, thanks to friends.
 

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Isn't that obvious?



Ask that question about any ICE for that matter.
Well, yes; obviously some temperature equilibrium scheme remains necessary for internal-combustion engines, but . . . to what extent? How precisely must the temperature be stabilized for durable and reliable operation?

As to asking the question of component failure/malfunction of any ICE; indeed, one could--however, since this is a KLR650 forum, the granularity of identifying engine-specific incidents traceable to the stock cooling system might be germane to the discussion, I thought.

Again, only a question: Nothing against the Thermo-Bob--inviting correlation of the device's enhancement of service life and reliability. A competently designed and manufactured, thoroughly-tested, responsibly-marketed accessory, AFAIK. Works as advertised, stabilizing coolant temperature more thoroughly and at a higher level than the stock cooling system.
 

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Is there any particular reason the Tbob runs at a higher temp? I read the link but didn't see the reasoning for that. Mighta just missed it.

And like Damocles, I'm not trying to pick it apart, just honest curiosity.
 

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Is there any particular reason the Tbob runs at a higher temp? I read the link but didn't see the reasoning for that. Mighta just missed it.

And like Damocles, I'm not trying to pick it apart, just honest curiosity.
The Thermo-Bob has a 195-degree F. thermostat, vs. . . . I don't know what the stock thermostat is, something like 165-degree F., I think. Not sure of the exact temperature ratings of the respective thermostats, but I believe the Thermo-Bob's opens at a higher temperature than the stock one.

Further, in the Thermo-Bob literature, I think the premise is advanced--the oil temperature with the stock KLR650 cooling system is not sufficiently high for optimum oil performance.

All this may be abundantly true; however, my D2500 Cummins Diesel engine temperature gauge stays at 150 degrees, summer or winter. (The needle, however, is indeed steadier than that of my Generation 1 KLR650!) The design points chosen by the Dodge and the Kawasaki engineers may be for entirely different reasons, and a considerable distinction exists between a Diesel truck engine and a gasoline motorcycle engine; I do not conflate the lubricant temperature requirements of the two.
 

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Yeah, I saw in the literature that the stock tstat is 160 and the Tbob tstat is 195. I didn't word myself carefully again, as what I was curious about is why the inventor of the Tbob decided to run his tstat at a higher temp. I guess it was to increase oil temps to what he claims he was told was optimum, but he continues to say that the stock cooling system is not capable of maintaining the 160 temp of the stock tstat and that engine temps are actually hovering in the 200-215 range anyway. So that seems like a moot point.

And that brings me to the other bit I'm curious about. Users of the Tbob say they see higher running temps. Which is understandable since much of the water leaving the engine looking for a radiator just gets dumped right back in to the engine, never being able to see any cooling at all. I understand that's the cycle that is responsible for the consistent temps, but bypassing an already borderline capable cooling system seems odd.

But hey, like the old saying: " the proof is in the pudding". So, according to his tests, the oil temps don't go over-temp and the overall engine temps are more consistent. I reckon facts are facts, whether you can understand the physics or not.
 

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So, according to his tests, the oil temps don't go over-temp and the overall engine temps are more consistent. I reckon facts are facts, whether you can understand the physics or not.
If the Thermo-Bob thermostat opens 35 degrees F. higher than stock, I'd expect a nominally higher average coolant temperature than with a stock cooling system. Thermo-Bob users have reported higher, and more stable, temperature gauge indications with a Thermo-Bob.

Further, unless I'm mistaken, a claimed advantage of the Thermo-Bob is higher (more optimal) oil temperature; if I'm in error, I stand corrected.

Is your premise: The Thermo-Bob, with a 35-degree higher thermostat-opening threshold, results in a cooling system maintaining the coolant at the same or lower temperature than the stock cooling system? Didn't think so, myself, but I defer to credible evidence, if available.
 
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