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Looks like an electronics cooler to me, not a KLR cooler. I am fond, however, of the term "18 Zigzags/Inch."

They should rate trails like that: "25 Zigzags/Mile."
 

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This is for high performance computers. I would not even give it a second look for the bike or for a computer. The good ones are about 2 inches thick and use 3 fans for cooling.
While my wife was living and required constant care I made some very high power computers with water cooling.
 

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Discussion Starter #4
A radiator is a radiator so I might order one for fun, not that I have cooling problems. The flow rate including inlet/outlet size is one parameter, mounting system another and physical construction as to how much abuse it will endure are others. I thought I might use a parallel flow rather than series because that would reduce the restriction to flow rather than to increase. I have a 195 F thermostat and bypass system of my own design so my system is more stable than stock systems.

I keep looking at KLX250 and others with double radiators and being one to never leave anything alone which can be improved.... ;-) Have made many discoveries as to why "that won't work". Many of those lessons have taught more than other experiences.
 

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I'm confused. What would be the purpose of dual radiators, whether in a series or parallel?

If the standard radiator is of adequate efficiency, it would seem to me that adding more components would just add more potential points of failure.
 

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Discussion Starter #6
Right of course, but for slow speed and hard climbing, the temperature can climb quite high. Once the thermostat is wide open (above about 160F for the stock bike but 195 F for mine give or take), the next increment is the fan thermal switch which kicks the fan on at above 210 F. If that is insufficient to extract sufficient heat from the system, the temperature will climb until equilibrium is reached.

Jeff Saline and some others have added radiator capacity in the form of a second radiator while Kawasaki added a larger radiator for the Gen2.

Adding a second radiator to increase the heat transfer area must not reduce flow to the point where the advantage of the added area is less than the reduced flow.

If one adds a second radiator in parallel, the flow will be shared/divided so the resistance to flow will be less than for one radiator or for the two in series.

Big problem is mounting the radiator and relocating the overflow tank. Only time and some fitting.

But of course you already know this and I'm only walking through the process in my head.

That, and it might be interesting to see how the temperatures are affected.

Before you point out that I'd be better off boxing in the engine for much of the year to actually let it stay at operating temperature, I'll admit that too. :)

Mostly to see how the change affects things and whether predictions pan out.




I'm confused. What would be the purpose of dual radiators, whether in a series or parallel?

If the standard radiator is of adequate efficiency, it would seem to me that adding more components would just add more potential points of failure.
 

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Normk,
I do know from reading, that Willy's on this site and JeffSaline on .net both run dual radiators. Contact them. I think they are mounted on the RH side.

I personally would not mined a second radiator, after seeing near Redline, climbing Imogene Pass, down in Colorado 3 years ago (turned-off 3 times). I hope to go back down this August.

Chuck B. on .net may also run 2 Radiators.
 

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Has anybody tried to install a better fan on the existing radiator? I wonder if you could make any gains that way? I guess you couldn't make it much larger, but perhaps one with more efficient blades spinning at a higher rate to draw more air through the radiator at low speeds?

I'm guessing it's not feasible or effective since I've never heard of anybody doing it.
 

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Discussion Starter #9
I've attempted to address this issue by placing car door edge rubber over the edge of the fan shroud. This is the stuff which has a soft, pliable side which seals the shroud to the radiator core and so blocks the space between the steel shroud ring and the radiator.

If one does a bit of smoke testing or even uses a ribbon or bit if tissue, one will discover that the fan's action in extracting air from the fan shroud results in a significant amount of air entering between the fan shroud and the radiator. Obviously this reduces the air flow through the radiator core by reducing the low pressure area in the shroud.

It might be well to remind that the fan causes air to flow through the radiator core by reducing the air pressure at the back of the radiator (inside the shroud). Atmospheric pressure forces air to flow through the radiator core into the low pressure area inside the shroud. The fan does not "pull" the air through the radiator.

One cannot do this for the Gen2, obviously, because the fan shroud is integral to the blades.

I'd thought about adding another fan or the possibility of usinrg a "box" system on the back of the radiator such as that used on Volkswagen Rabbits and other cars. This system has an enclosure over the back of the radiator which encloses the complete rear of the radiator so that the fan's action is applied to the whole of the radiator core rather than only to the ring shroud area as for the KLR.

This system was/is common to cars but the difference in the VW system is that there are additional vent holes in the rear of the shroud. Rubber flaps fall over the vents so that the fan's action does not result in air entering into the back of the shroud because the rubber flaps block the vents. When the radiator is moving through the air because the car is in motion, the air pressure in the shroud becomes higher than that behind/outside the shroud so the resulting air pressure inside the shroud opens the flaps and the full air flow through the radiator is unrestricted by the smaller fan outlet hole.

I may take another look at that possibility as it would be fairly simple to make a shroud from Lexan if only for testing. I do lack the precise instrumentation and the expertise to properly evaluate the effects so am trolling to see if Bill Watson might weigh in...?

Any chance you're reading this Wattman?
Perhaps I'll email this thread link and ask if he has time. Nothing better to save wasted effort and to learn that to ask someone who really knows. :)



Has anybody tried to install a better fan on the existing radiator? I wonder if you could make any gains that way? I guess you couldn't make it much larger, but perhaps one with more efficient blades spinning at a higher rate to draw more air through the radiator at low speeds?

I'm guessing it's not feasible or effective since I've never heard of anybody doing it.
 

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Speaking from ignorance since I don't have a gen1, if the main concern is low speed high load operation - climbing a long steep rocky grade- you might consider mounting a second fan on the front of the radiator.
 

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Discussion Starter #11
I think I'll go down to some friends' shops tomorrow and measure some radiators and fans. I need to find an oil pressure gauge as though I had one on hand.

Your mention of a second fan lead me to considering the power required for a second fan, given the limited KLR output. Mulling over some of the suggestions/ideas it might be more efficient to try a thicker radiator as some have done in order to make better use of the existing fan, or to use a larger radiator and fan on the exisiting side....more things to think about. Mostly thinking about what might be interesting to do in the way of improvement. My bike doesn't seem to be much bothered heat and climbing so more of an exercise than requirement. The 195 F 'stat and by pass seems to have improved the cooling significantly but maybe there's an ideal candidate for a rad and fan waiting to be measured. :)





Speaking from ignorance since I don't have a gen1, if the main concern is low speed high load operation - climbing a long steep rocky grade- you might consider mounting a second fan on the front of the radiator.
 

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My bike doesn't seem to be much bothered heat and climbing so more of an exercise than requirement. The 195 F 'stat and by pass seems to have improved the cooling significantly but maybe there's an ideal candidate for a rad and fan waiting to be measured. :)
Has anyone had overheating problems with the KLR650 stock cooling system, in typical service? I have not; temperature gauge needle stays out of the red zone, no matter what the ambient temperature or load I've experienced. Just wondering at the problems others have faced.

Just a question, Normk: Can you be more specific regarding how your 195 degree thermostat and bypass has improved cooling? I can see how the scheme stabilizes coolant temperature more fully, and at a higher operating temperature, but . . . after the thermostat opens, I cannot see how cooling is enhanced, regardless of thermostat opening temperature or radiator bypass.

Others have claimed enhanced cooling from ThermoBob installation, but . . . after the thermostat opens, looks to me like the engine remains at the mercy of coolant circulation and air flow (unchanged), regardless of thermostat/bypass configuration.

Again, not doubting cooling enhancement with a bypass and higher-temperature thermostat, just asking how more cooling capacity is available from these modifications, when coolant circulation/radiator surface/airflow/etc. remain unchanged.
 

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I have had no problem with KLRs and cooling. If you want to put a fan in front of the Radiator you will not get the effect that you are looking for. Air must be drawn through a radiator for proper effect.
Cooling problems can be caused by media being placed in front of the radiator and restricting the air flow. Also if you run your coolant too low for an extended time you can get corrosion in side the tubes restricting the flow.
Overall you need to run a coolant that is compatible with the radiator and engine. Many automotive coolants are not. As noted by others changing the thermostat temperature can help. Adding a bypass or a timed pump for after the bike is turned off can also help, but good cleaning and proper maintenance will solve most problems.
 

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As noted by others changing the thermostat temperature can help. Adding a bypass . . . can also help, . . .
That's the part I don't get, iride4u.

Don't see how a thermostat opening at a higher temperature enhances cooling capacity of existing water pump, radiator, and fan.

And, after the thermostat opens, radiator bypass doesn't, well, bypass--all coolant is channeled to radiator.

Again, I accept a radiator bypass and higher-temperature thermostat stabilizes coolant temperature more fully, and at a higher nominal operating temperature. Yet, seems to me the job of dissipating those BTUs is left up to the unchanged water pump, radiator, and fan (and air circulation from motion).
 

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That's the part I don't get, iride4u.

Don't see how a thermostat opening at a higher temperature enhances cooling capacity of existing water pump, radiator, and fan.

And, after the thermostat opens, radiator bypass doesn't, well, bypass--all coolant is channeled to radiator.

Again, I accept a radiator bypass and higher-temperature thermostat stabilizes coolant temperature more fully, and at a higher nominal operating temperature. Yet, seems to me the job of dissipating those BTUs is left up to the unchanged water pump, radiator, and fan (and air circulation from motion).
I think when Normk said "The 195 F 'stat and by pass seems to have improved the cooling significantly", he was referring to the quality of the cooling system rather than the quantity.

While the bypass still bypasses a little around the radiator with the t-stat fully open, the physically larger thermostat likely allows a little better flow and the total cooling capacity should be very close to stock.
 

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While the bypass still bypasses a little around the radiator with the t-stat fully open, the physically larger thermostat likely allows a little better flow and the total cooling capacity should be very close to stock.
Good points, GoMotor!

Surely, some minimal flow might exist in the bypass plumbing when the thermostat is open. However, recirculating the hot coolant back into the engine without benefit of heat-exchanging in the radiator would do little to enhance cooling capacity, IMHO, although the bypass plumbing itself may offer some heat-exchanging effect.

As to the larger diameter of the Thermo-Bob thermostat, the device is placed "downstream" of the previously-existing restrictions in the cooling system; thus, I doubt significant flow increase would result.

A Thermo-Bob or alternate higher-temperature thermostat and radiator bypass may indeed offer greater cooling capacity; I just don't fully grasp the operational concept.
 

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Good points, GoMotor!

Surely, some minimal flow might exist in the bypass plumbing when the thermostat is open. However, recirculating the hot coolant back into the engine without benefit of heat-exchanging in the radiator would do little to enhance cooling capacity, IMHO, although the bypass plumbing itself may offer some heat-exchanging effect.

As to the larger diameter of the Thermo-Bob thermostat, the device is placed "downstream" of the previously-existing restrictions in the cooling system; thus, I doubt significant flow increase would result.

A Thermo-Bob or alternate higher-temperature thermostat and radiator bypass may indeed offer greater cooling capacity; I just don't fully grasp the operational concept.
I don't think I made myself clear. I do think the small flow through the bypass will reduce the cooling capacity, but very slightly. I don't think heat rejected through the bypass hose is significant. I do assume the larger thermostat in the Thermo-Bob housing has a bit larger wide-open opening then the smaller OEM thermostat allowing a little higher flow, but that is only an assumption.

For what it is worth, I have a 1/4" radiator bypass with the OEM thermostat housing and thermostat on one of my gen2 KLRs and have not had any over heating problems.
 

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Discussion Starter #18
I have tried to be careful in describing but seem to have given the wrong impression, Damocles. The higher temperature thermostat & by pass have improved/enhanced the cooling system's performance but have not increased the ultimate heat rejection once the thermostat is wide open. That effect, as has been noted, is limited by the thermal gradient or temperature difference across the radiator.

I am not running a Thermo-Bob for several reasons, mainly centered around my desire to experiment. I have not measured the flow rate through the Thermo-Bob as compared with my system but don't think that either would have a significant/measurable advantage in flow rate because I would expect cooling system restriction due to radiator, passages, and hoses to be similar.

I'm reluctant to take this discussion into the area of thermostat and by pass because it may create the impression that I am criticising the Thermo-Bob which is, IMO, backed by expertise and empiracal data beyond my capacity.

Looking around the garage but don't seem to have any more rad fans but may be able to borrow one. I might plumb one to the front of the rad for interest as air moving through the radiator has the same effect regardless of how it is moved. It doesn't matter whether the fan is "pushing" or "pulling" because these are simply short a hand indicators of the fan's location since one cannot "pull" a gas.

If the fan is behind the radiator (pulling air), it produces a low pressure area into which atmospheric pressure forces surrounding air. It the fan is in front of the radiator (pushing air) it creates a low pressure area at the fan inlet and a high pressure area at the outlet. The difference in pressure causes the air movement in either case.

Power engineers refer to the fan behind as "induced draft" and the one in front as "forced draft". In fact, a higher pressure difference and so more air flow rate can be achieved by the FD fan/fan in front of the radiator, because this fan position can develop a pressure difference as high as one requires in theory.

Once the fan which is placed behind the radiator creates sufficient extraction rate of air from the pocket between fan and radiator to match atmospheric pressure the air flow rate will be limited. If one considers that the fan behind the radiator can only achieve 100% evacuation of air or a perfect vacuum, this will be seen to create a maximum pressure difference across the radiator of 14.7 PSI or atmospheric pressure at what ever is the elevation.

The pressure which could be created by a fan (compressor) in front of the radiator is virtually limitless although many practical limitations will intervene.

Just wanting to make the point, with justifications, that the fan can be placed in front of or behind the radiator with equal success.
 

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Discussion Starter #19
Just in case someone missed the point: has anyone else experimented with sealing the radiator shroud to the radiator core?

I've been posting this modification, usually using recycled door rubber in order to prevent air from entering between the shroud and the radiator.

The second advantage to this modification is that it helps to protect the radiator from damage should the shroud or mounting break.

Anyone?
 

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I personally think that proper maintenance of the cooling system will solve most peoples problems.
 
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