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I'm just curious as to what anybody else with a engine
temperature gauge is seeing for numbers.

I rode some yesterday and temps maxed out at 159 with
a Trail Tech Vapor.

The Highest I've seen mine is 152, riding single track at 90 degrees, also using a vapor to read temps. 144 is where the bike normally runs.

where is the thermocouple placed?

Mine is in the middle of the crossover hose.

This has been discussed before; I used a mechanical automotive water temp gauge with the probe located in the hose just outside the water outlet in the top of the head, and regularly saw temps as high as 260 degrees on long hard climbs; rarely below 200 unless I was just cruising. I was shocked, and checked the gauge with boiling water; it's accurate. Bike runs great and jetting is, if anything, a bit rich.

Jaguar wrote:where is the thermocouple placed?

Also in the hose connecting the two radiators.

I would have guess'd anything between 160-180 would be normal .
Since it's a resistance to flow system with no thermostat or cooling fan.

I would say 185 is the norm for Sumer and less for winter. The inline sensor is halfway up the pipe out of the head to radiator. I believe this is where they are supposed to go.
I have those larger Chinese KX125 tanks.

chkdx wrote:This has been discussed before; I used a mechanical automotive water temp gauge with the probe located in the hose just outside the water outlet in the top of the head, and regularly saw temps as high as 260 degrees on long hard climbs; rarely below 200 unless I was just cruising. I was shocked, and checked the gauge with boiling water; it's accurate. Bike runs great and jetting is, if anything, a bit rich.

Wow ! 50/50 coolant boils at 265 degree's

that's really interesting. my fuel was boiling last weekend, ambient temperature was around 90f, heavy single track, lots of hill climb failures.

there was only 1/4 gallon of fuel left though, so midi less fluid to displace the heat from the engine.

the radiator fluid was full, with no loss, when the bike cooled down enough to check.

with two huge radiators and just over walking pace for air flow, i would imagine it would never over heat if the radiator fins are clean.

does anyone have a boiling issue on their kdx ?

Using Vapor I run around 155* to 165* on the 220 with sensor in hose @ head water outlet. The hottest I have seen is in traffic 171*

Engine ice coolant

s10gto wrote:Using Vapor I run around 155* to 165* on the 220 with sensor in hose @ head water outlet. The hottest I have seen is in traffic 171*

Engine ice coolant

Stock engine ?? That sounds about rt.

This is good info; when the topic was discussed before, literally nobody except me had actually measured their water temp. I had to go to a 1.6 bar rad cap to stop boilover, but so had others, so I didn't know for sure if my alarmingly high temps were normal.

I'm beginning to think my water pump isn't working right, gonna check into that.

C George wrote:

s10gto wrote:Using Vapor I run around 155* to 165* on the 220 with sensor in hose @ head water outlet. The hottest I have seen is in traffic 171*

Engine ice coolant

Stock engine ?? That sounds about rt.

Yup all stock. Just a wiseco of course.

Riding yesterday at slower speeds on trails it reached 188 degree's .

Then after that on 30-40 mph stretch it dropped to 172.

But this is on a highly modded engine.

Testically.............50/50 really boils around 220deg, pure coolant up in the 300's, but the more water you can run the better the cooling effect will be due to the viscosity/heat transfer properties of water. The boiling point of water and/or coolant mix is raised 3deg for every 1psi of cooling system pressure (IE 12psi cap= +36 deg boiling point). Pure water will cool the best until it boils, but of course does no good for freeze protection or pump lubrication.

fuzzy wrote:Testically.............50/50 really boils around 220deg, pure coolant up in the 300's, but the more water you can run the better the cooling effect will be due to the viscosity/heat transfer properties of water. The boiling point of water and/or coolant mix is raised 3deg for every 1psi of cooling system pressure (IE 12psi cap= +36 deg boiling point). Pure water will cool the best until it boils, but of course does no good for freeze protection or pump lubrication.

Thats what I was basing the 265 degree rating on ,,,, 50/50 coolant mix with a stock 16lb radiator cap.

Your comments on better heat dissipation with more water are correct , just theres no need to run anything
but 50/50 in these bikes.

The factory fill is with blue Aisan coolant but I'm sure any long life coolant will be fine.

I use 30% of the GM (gold color) coolant, since I don't expose my bike to -10° temps much. Really keeps the bike cooler that the standard "green stuff".
Also, I make sure that it is silicate free!

6 Riders wrote:I use 30% of the GM (gold color) coolant, since I don't expose my bike to -10° temps much. Really keeps the bike cooler that the standard "green stuff".
Also, I make sure that it is silicate free!

Just lowers the boiling point quite a bit but hopefully it never gets close to that temp.

And make sure you don't leave your bike in a cabin at 30 below.

Indeed....FYI, wasn't discounting your posted boiling point, but was throwing some coolant education out there.

No worries ,,,,, info is good for all of us.