Therm-a-bob experts: Question. - 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 57 Old 07-31-2016, 10:15 PM Thread Starter
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Therm-a-bob experts: Question.

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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post #2 of 57 Old 08-01-2016, 06:50 AM
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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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post #3 of 57 Old 08-01-2016, 07:38 AM
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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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post #4 of 57 Old 08-01-2016, 11:46 AM
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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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post #5 of 57 Old 08-14-2016, 08:47 AM Thread Starter
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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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post #6 of 57 Old 08-14-2016, 01:26 PM
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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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post #7 of 57 Old 08-15-2016, 10:16 AM
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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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post #8 of 57 Old 08-16-2016, 02:22 PM
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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.

'11 KLR 650: KLR Full Bag Kit, 22 Mod, Thermo-Bob w/ Overlay, Angular Mirrors, Studebaker Doo, Tusk Drain Plug, UNI Filter, K761's, ODI Emig Grips, LED Cluster & Tag, Digital Clock w/ Temp, Eibach 400# RR, Progressive FR w/ adj Pre-load caps, ZG Double Bubble

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post #9 of 57 Old 08-16-2016, 03:05 PM
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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. 300-400F 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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post #10 of 57 Old 08-16-2016, 03:13 PM
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From the source;

http://www.watt-man.com/uploads/TB_Testing.pdf

Cheers,
Dave
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