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Thermo bob mod for 2007 KLR

7K views 23 replies 6 participants last post by  Damocles 
#1 ·
Another question from a newbie: Is the thermo bob mod only necessary in colder climates or is it an all around good mod? As far as I understand it it brings the engine up to temperature quicker. Here in South Africa it is quite warm so I am wondering if this mod would cause more harm then good.
 
#2 · (Edited)
Properly installed (not crossing up the hoses emanating from the water pump) the T-Bob has never done any harm. I live in a climate similar to ZA and often ride in temperatures in the 40℃ range.

The coolant temperature comes up to midscale (mine is a 2009) quickly on the temp indicator. The cooling system controls the upper temperature quite well, so the overall effect is that the engine operates, 95% of the time, at mid-scale. It will pop up higher when in stop and go traffic, but that is completely normal and not related to the T-Bob.

I also ride in temperatures in the 0℃ range from time to time in vain attempts to kill myself*. Again, the engine comes up quickly to mid-scale and stays there.

*To date, I have never been killed. Not even once.
 
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#3 ·
While I think the T bob is even more beneficial in cold climates and cold weather use, it is still a good thing even in relatively warm temps since warm ambient is still cold engine temps. .....no downside other than the cost that I can tell and maximum engine temperatures should be unaffected. Bill has info on Gen1 cooling system mods to increase overall cooling capacity; http://watt-man.com/uploads/Margin.pdf


Dave
 
#5 ·
Another question from a newbie: Is the thermo bob mod only necessary in colder climates or is it an all around good mod? As far as I understand it it brings the engine up to temperature quicker. Here in South Africa it is quite warm so I am wondering if this mod would cause more harm then good.
I was wondering this same thing for my 07 as I live in South ga. I do notice riding now it barely hits the line in the lower narmal range. That will probably be my next upgrade. I was also thinking of putting the watt man overlay in too.
Just a fun fact:

After the thermostat opens, the KLR650 is at the mercy of air flow and coolant circulation, both unchanged, Thermo-Bob or not. In other words, the Thermo-Bob does not enhance cooling IMHO (although some insist otherwise).

The Thermo-Bob stabilizes engine coolant temperature more thoroughly, and at a higher temperature than the stock cooling system. Competently designed and manufactured, responsibly marketed, thoroughly tested, service life effects remain unquantified.

My ex-South African riding partner (80,000 miles on his '08 model) LOVES his Thermo-Bob; my '07 muddles through without one.

As Tom Schmitz posts above, a Thermo-Bob certainly does no harm (if installed correctly); your call entirely whether to install one or not.
 
#13 ·
the cause is a bad/ovaled/tapered/deformed bore coupled with a poor ring redesign..... resulting in a lack of sealing at the bottom end of the stroke. the bore issues probably are exacerbated by thermal shock which the Thermobob helps mitigate.
Don't hear much about excessive oil consumption nowadays; maybe the piston ring re-design cured the problem, even with the stock cooling system . . . or not! :)
 
#18 ·
coincidence but Mike just posted this today;

Ever measure a few hundred cylinders, some with the T-Bob and some without? I have...... :) Most out of round with the Thermo-Bob was .0012. Worst out of round without the T-Bob was .008. This excludes the obvious seized/dirt wear, includes just the normal still pretty smooth stuff. There as always a reason for the stuff I do......


Dave
 
#20 ·
coincidence but Mike just posted this today;

Ever measure a few hundred cylinders, some with the T-Bob and some without? I have...... :) Most out of round with the Thermo-Bob was .0012. Worst out of round without the T-Bob was .008. This excludes the obvious seized/dirt wear, includes just the normal still pretty smooth stuff. There as always a reason for the stuff I do......

Mike gives only two, "point estimates," extreme examples; the overall statistical picture (e.g., averages, medians, etc.) of the several hundred cylinders measured would give more weight to the premise of the Thermo-Bob's reduction/elimination of cylinder distortion.

Apparently, the out-of-round distortion comes quite early; some '08-'09s used excessive oil right off the showroom floor . . .

Given the conclusion (absent a Thermo-Bob, the cylinder bore will go out-of-round with consequent excessive oil consumption), a Thermo-Bob should be installed early and often.
 
#21 · (Edited)
Honestly I think the bore has a propensity to go out of round on the bottom end regardless......but the T bob may lessen the distortion to the extent that the rings can compensate. Cary theorized that after a number of heat cycles the bore tends to become relatively static - which is why it stays fairly stable after a 685 rebore job. The '08's and '09's have a well deserved reputation for oil burning due to the ring (re)design, not because the bores are way worse than earlier or later bikes.....this is based on my review of some of KLRCary's material as well as my discussions with Eaglemike. Cary described the bore distortion as a design issue. Mike's belief is that if you put an earlier or later piston/ring set into a virgin 2008 or 2009 bore that it would have no greater chance of being an oil burner than other years.

To recap my thoughts;

- early Gen2's ring design was poor leading to a much higher incidence of oil consumption; as the bores distorted the rings couldn't control the oil.
- KLR650's have a propensity for some degree of bore distortion due to the design (lack of support on the bottom end of the sleeve and the thickness of the sleeve)
- the bore shape tends to stay relatively static after a certain number of heat cycles which is why the 685 kits usually solve oil consumption issues (and Mike's rings seal better)
- Aftermarket sleeves such as the 705 sleeve are beefier and don't distort much, if at all.
- the Thermobob helps lessen bore distortion by greatly reducing the delta T of entering and leaving water (cold shocking the cylinder). It's logical, given Cary's thoughts on the heat cycle issue, that the benefit of the thermobob is much greater if it's installed when new or very early in the engine's life. That said, it can only help regardless of when it's installed (do no harm! :) )

....at least that's the synopsis I've come up with after some research and discussions with the guys that have the first hand knowledge and experience on the subject.



Dave
 
#22 ·
WHAT? You're not even going to MENTION the, "More optimized oil operating temperature," argument in favor of the Thermo-Bob? :)

(My riding partner uses the justification relentlessly!)

All the arguments for the Thermo-Bob attest to the device's merits, by INSPECTION of their content. The actual PERFORMANCE data (as in, maintenance issue impact) remains difficult to capture.

I understand Thermo-Bobs fit Versys 650s (another Kawasaki design without radiator bypass). I wonder if similar Thermo-Bob performance, and the result of no Thermo-Bob, have been examined/reported on this model.
 
#23 ·
Sure, it's good for the engine if the oil is kept at optimal temperature; I was limiting my ramblings to the cylinder bore/ring/oil consumption issue. The data is almost impossible to collate; you'd need a wide variety of KLR's to be tested in a scientific environment.....which will never happen. You can measure the temperatures and logically extrapolate potential effects but at some point you have to take it on faith/logic based solely on empirical data.

I'm sure the T bob reduces temperature swings and optimises oil temperature on the Versys as well......but the Versys MAY not (and probably doesn't) have the same bore/ring issues that the KLR does.....which takes one back to the "it can't hurt and probably helps" line of thinking. Proof that your engine will last 21.897% longer with a Thermobob? ....yeah, nothing that concise will ever be available.

Dave
 
#24 ·
Thanks for your reasonable and rational discussion, DPelletier!

A far cry from the strident insistence a Thermo-Bob is MANDATORY; running without the device commits ABUSE to the engine; no KLR650 engine would EVER use excessive oil if fitted with a Thermo-Bob, etc.; comments all seen on another KLR650 forum, whose name shall remain anonymous! :)
 
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