Just a couple questions - Kawasaki KLR 650 Forum
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post #1 of 34 Old 07-07-2013, 03:00 PM Thread Starter
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Just a couple questions

Rode my KLR 105 miles last Sunday and 220 today, noticed that every time I come to a stop the fan is running or starts within seconds of stopping, do they normally run that close to fan cut on temp? The gauge is usually right in the center when moving at good speed and gets just a little higher when going slow or stopped. I am thinking the fan comes on a little earlier than it needs to.

#2, is the rear rack solid metal or is it hollow? Wondering if I can drill and tap some holes to mount a larger rack on.
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post #2 of 34 Old 07-07-2013, 03:09 PM
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I don't have the stock gauge anymore but I think straight up is about 210. Fan comes on at 220. I live in a hot climate so what you are saying is normal to me. Its hollow, you have to through bolt it to be safe. I cant remember the rated rack limits but it is not much. I would not get carried away with a lot of weight on it.
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post #3 of 34 Old 07-08-2013, 01:20 PM
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Quote:
Originally Posted by Dave0430 View Post
...... noticed that every time I come to a stop the fan is running or starts within seconds of stopping, do they normally run that close to fan cut on temp? The gauge is usually right in the center when moving at good speed and gets just a little higher when going slow or stopped. I am thinking the fan comes on a little earlier than it needs to.

do you have a thermo-bob or other aftermarket thermostat??

2013 KLR650
1994 YZ250
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post #4 of 34 Old 07-08-2013, 03:41 PM
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Originally Posted by a4twenty View Post
do you have a thermo-bob or other aftermarket thermostat??
According to Clymer, the thermal fan switch activates at 201-212 degrees F. (Generation 1).

Thus, any thermostat opening at any temperature below 201 degrees F. (including the Thermo-Bob's) would have no significant effect on fan activation, seems to me.

After the thermosat opens, Themo-Bob (or other radiator bypass) or not, engine cooling appears at the mercy of the water pump coolant circulation and radiator air flow alone, seems to me. An operational thermal switch kicks in regardless when the coolant around it reaches 201 degrees F., or thereabouts.

My perception only; clarifications and corrections welcomed.

-----------------------

Coolant temperature correlation (lineraly across arc, from 150 to 270 degrees F.), from Wattman''s (Thermo-Bob) website:



These coolant temperatures, of course, are from coolant about the cylinder head, where the temperature sensor is located. The temperature at the bottom of the radiator, where the thermal switch rests, is likely lower, especially at idle.

I think the coolant temperature is highest at the cylinder head, near combustion, and lowest at the bottom of the radiator, having exchanged heat as the coolant descends through the radiator passages; YMMV!

-----------------

Should have mentioned; a paper temperature gauge background, calibrated in degrees F., is available from Thermo-Bob, who provides a detailed installation procedure. The new background can be pasted behind the temperature gauge glass, and the coolant temperature read in degrees, instead of red markers.

Last edited by Damocles; 07-08-2013 at 04:43 PM.
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post #5 of 34 Old 07-08-2013, 04:12 PM
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Originally Posted by Damocles View Post
Thus, any thermostat opening at any temperature below 201 degrees F. (including the Thermo-Bob's) would have no significant effect on fan activation, seems to me.
except perhaps in the way the OP has mentioned / questioned....

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Originally Posted by Dave0430 View Post
......noticed that every time I come to a stop the fan is running or starts within seconds of stopping, do they normally run that close to fan cut on temp? The gauge is usually right in the center when moving at good speed and gets just a little higher when going slow or stopped.
running the aftermarket 195F thermostat ( gauge in the center ) would likely cause what the OP is seeing. with the engine running only a few degree's below the fan switches activation temperature will cause the fan to come on with almost every but the shortest stop.

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post #6 of 34 Old 07-08-2013, 04:37 PM
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Quote:
Originally Posted by a4twenty View Post
except perhaps in the way the OP has mentioned / questioned....



running the aftermarket 195F thermostat ( gauge in the center ) would likely cause what the OP is seeing. with the engine running only a few degree's below the fan switches activation temperature will cause the fan to come on with almost every but the shortest stop.
Except . . . the temperature gauge reads the coolant temperature at the cylinder head; the thermal switch is located at the bottom of the radiator, responding to the coolant temperature after the liquid passes through the radiator passages.

Clymer says:
Quote:
During engine operation, hot coolant from the engine enters the radiator through the upper hose. The coolant loses heat as it circulates to the bottom of the radiator.
I'd expect a considerable temperature differential in the coolant surrounding the cylinder head, and in the coolant after passing through the radiator passages to the lower radiator where the thermal switch is located.

Otherwise, the radiator would perform no heat-exchange function as far as I can see--the engine would be ingesting coolant at the same temperature as when pumped into the radiator.

Regardless,after either the stock 160-degree or an aftermarket 195-degree thermostat opens, I'd expect the thermal switch to close at the same 201-to-212-or-so degrees coolant temperature at the bottom of the radiator.

Last edited by Damocles; 07-08-2013 at 05:04 PM.
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post #7 of 34 Old 07-08-2013, 08:15 PM Thread Starter
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Originally Posted by a4twenty View Post
do you have a thermo-bob or other aftermarket thermostat??
Not that I know of, I have only had it a week as of yesterday.

You guys are making way too much of this, (don't worry it's not unusual), I only wanted to know if it is normal, don't need a thesis on why. I understand fully the operation of all this stuff, what I don't know is do all or most KLRs act similarly.
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post #8 of 34 Old 07-08-2013, 08:28 PM
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i gotta be honest, i don't know where you're going with this or how you got where you are but...

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Originally Posted by Damocles View Post
Except . . . the temperature gauge reads the coolant temperature at the cylinder head
the temperature gauge really has nothing to do with the cooling system of the bike, it just gives us a visual indication of where the temperature is in the operating range. the OP used the gauges position to describe his question...

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Originally Posted by Dave0430 View Post
The gauge is usually right in the center when moving at good speed and gets just a little higher when going slow or stopped.
would a hotter thermostat not explain why his gauge indicates like that and why it only moves a little bit more before the fan comes on?

2013 KLR650
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post #9 of 34 Old 07-08-2013, 08:29 PM
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Originally Posted by Dave0430 View Post
Not that I know of, I have only had it a week as of yesterday.

You guys are making way too much of this, (don't worry it's not unusual), I only wanted to know if it is normal, don't need a thesis on why. I understand fully the operation of all this stuff, what I don't know is do all or most KLRs act similarly.
O.K. Dave0430; as long as your temperature gauge needle stays out of the far right red block, FEAR NOT!

The stock KLR cooling system is known for some fluctuation in temperature, but . . . I know of no maintenance issue as a result of this heat cycling. (Conflicting opinions may exist. )

As to rack, I think it's tubular (not that you couldn't drill solid steel), but . . . if you want a really robust rack, a CycleRack will carry a moose quarter without undue stress; lifetime guaranteed, and . . . none has ever broken in service:

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post #10 of 34 Old 07-08-2013, 11:07 PM
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Originally Posted by a4twenty View Post
would a hotter thermostat not explain why his gauge indicates like that and why it only moves a little bit more before the fan comes on?
I see your point, a4twenty; maybe so!

A "hotter" thermostat will be reflected in a higher temperature gauge needle position during engine operation, but shouldn't cause premature fan activation, as the OP suspected, IMHO.

The coolant around the thermal fan switch is at a lower temperature than the coolant at the thermostat (and on the temperature gauge) when the thermostat opens.

Clymer:
Quote:
When the cylinder head coolant begins to exceed the ideal operating temperature [160 degrees F. stock, 195 degrees F. Thermo-Bob], the thermostat opens and allows the coolant to pass to the radiator, where it is cooled.
Unless the thermostat temperature exceeds the thermal fan switch threshold, I don't see how a hotter thermostat could cause the fan to come on "a little earlier than it needs to," a concern of the OP in his IP.

Again, my perceptions only; if flawed and erroneous, corrections and clarifications appreciated!
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