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engine component compositions, etc. ~230F is where a lot of engines start risking damage due to warping components.
I'll disagree with that statement.
The engine metals are perfectly safe up to 300-350F+ as long as the engine oil stays below about 250-275F in the sump.
Most air-cooled motorcycle engines operate in the 275-350F cylinder head temp range very frequently.
Liquid-cooled engines need pressurized Coolant/Antifreeze to stay below the boiling point of the coolant, to prevent hot spots from developing. Once any hot spot develops the whole system can spike quite quickly.

165F thermostats were an old hot rodder solution to inadequate cooling systems that couldn't keep up with heat output at full load; the extra overhead between running temp and harmful temps allowed you to run flat out without overheating the engine
I'll disagree with that statement also.
A 165F thermostat can not compensate for too small of radiator or too slow (or too fast) of coolant flow or too slow of air flow, be it in a KLR or any hot-rodded engine!
 

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I didn't say 165F thermostats would fix a inadequate cooling situation. I just said it was an old hot rodder solution which gives some extra overhead before the engine overheats.
Neither a 195F nor a 165F thermostat will give any "extra overhead before the engine overheats"! 165F isn't even hot yet.
195F is still not up to the boiling point of water only, even without a pressure cap!

Only a larger radiator or more efficient radiator or more cooling air flow can give "extra cooling capacity" to prevent overheating.

The Gen 1 radiator was almost too small, the Gen 2 & Gen 3 radiators are larger, much more efficient & more easily damaged.
 

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Actually, the thermostat controls the temperature at which coolant can flow out of the block so for all practical purposes, it sets the max engine temperature.
That part of your statement is incorrect. The thermostat attempts to control the Minimum operating temperature.



If the cooling system is adequate to regulate temperature under mild load conditions, but inadequate under heavy load or high ambient heat conditions (this describes most pre-70s vehicles), you might be able to buy yourself a couple more minute of high load operation before the engine overheats by running a 165F thermostat. It won't change the fact that the engine will overheat, because that's up to the cooling capacity of the system, but that's often enough to get you back from the end of a drag strip, or up to the top of the grade you're trying to climb.
The KLR's with temperature Gauges and stock & standard cooling systems (including the 157 -162F rated thermostat) will roll down the open highway all day long in 60-80 F ambient air temps with the temp needle hovering at about 1/4 scale (160'ish).
But when one rolls into town and has to stop for a mere minute or two at the first stop light the temp gauge will invariably climb right up to at or slightly above 1/2 scale (210'ish). Then the fan turns on & off and basically keeps the coolant hovering at its switch set points of 214-189F (and this is at the Bottom of the radiator, not temp gauge sender).

One could install a Thermo-Bob and use the OEM 160F thermostat and it would warm-up Quicker in the morning & remain more stable on the gauge in those first 20-30 minutes of operation. But rolling into town & being stopped at the first stop light it would still climb to the cooling fan set point as described above.
With a 195F thermostat installed the engine would simply not chill back down to 160F upon regaining sufficient road speed which cools the radiator & its fan switch.

Again, a 160F thermostat can not give any real advantage to reduction of possible over-heating (260F+) in these KLR engines. That is controlled by radiator size, coolant flow speed & air flow speed. The increased radiator size of the Gen 2 & 3's ensures that.
If you are climbing a mountain pass & the thermostat is wide open & the cooling fan is running because the bottom of the radiator is above thermostat temp, correct. Doesn't matter which thermostat is installed from that temp up, the engine will either stabilize at a higher temp, continue to heat, or cool down after load is reduced. Neither system is too hot until 260+F.


The thermostat in every water cooled internal combustion engine that operates using a wax capsule (which is every engine coolant thermostat that I'm aware of) is in an open or closed state, there is no variable attenuation.
I'll say that is incorrect.
I'll suggest that you ought to dangle a thermostat & a thermometer into a kettle of Coolant/Antifreeze and watch how slowly & gradually the wax capsule attains fully open or fully closed. The temp number on them is simply the beginning of opening (+/- a few degrees). They are perfectly happy to operate in partial open position if they receive Steady temp coolant which is what the Thermo-Bob provides.
 

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Am I wrong? Ultimately the thermostat opens when it is to the correct operating temp and closes if it gets a little cold. Doesn't that mean it is at a proper operating temp? I assume at 40 degrees, it should get at least the 160 degrees.
Modern (1965+?) proper operating temperature is closer to 195F+, but engine cooling systems NEED to have Radiator Bypass systems to operate Smoothly/Consistently, even with a mere 160F thermostat. Which one could use in the KLR Thermo-Bob, but that partially defeats its benefits.
 

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A warmer engine is a happier engine and the aluminum castings of the KLR & most other motorcycle engines are one Giant heat radiator in cooler weather!
 
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