Motor temp.

[KR-1R]

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buy a digital (or stepper motor) temperature gauge and new sensor
an accurate temp gauge and voltmeter are worthwhile upgrades

have you checked or fitted a different radiator cap?

you are aware of limitations of non-contact (infrared 'laser') thermometers ... emissivity and spot size/distance?

[Mouser]

@KR-1R,

Yes I'm well aware of the accuracy of the laser thermometer (distance etc.) This one is no bullshit, it is quite accurate (comparing to my RGV it indicates a temp of max 65°).

So the values are correct. Did more than one measurement.

I checked the radiator cap, it seems ok, haven't changed it.
But even if it would open "too soon" or "too late" this wouldn't affect the temp of the cooling system if it is well filled up and no aire in it, would it?

Thanks
Mouser

[headcoats]

Coolant leak washing the top of the piston ?

[Mouser]

No coolant leak, coolant level doesn't change.

[Mouser]

Could it be that the float level of the carburettor is incorrect, causing the mixture having too less fuel in high rmp's and then causing the combustion being hotter?

I think the carburettor needles are the right ones, cause riding it easily the engine does not get too hot.

What do you think?

Mouser

[KR-1R]

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'FGS' take the small water pump cover off and check out the impellor
maximum cost 11009-1929, less if youre careful and use some gasket goo
normal running water temp is 75-82°C

I cant think of a reason why pump might be broken (blades or driving gear) - but perhaps some krud (bolt! or something) is blocked in there. You could investigate the lower crankcase water gallery while its off.

without a thermostat or pump the KR motor is cleverly designed to make use of Thermosyphon effect (natural cycle/flow of cooler water from outlet of radiator into bottom of motor, heats up through the cylinders, heads and into top of radiator) - this alone is not sufficient to adequately cool it

[Mouser]

Ok, I'll take off the impeller and check the lower water gallery too.

It seems to turn normally (cover off) while kicking but just to be sure.

What do you think of the fuel carb level being too low and the mixture running with not enough fuel in high rpm's?

Thanks
Mouser

[Luders]

That could happen, but there would usually be evidence on the piston if that were the case.

[Mouser]

hm, ok, but I didn't drive a lot with the bike getting hot, maybe 3-4 times (testing) for about 10 minutes in the "red" area.

But the pics of the piston are in the thread, a few posts ago, both look similar.

Thanks
Mouser

[Luders]

Yeah based on those pics, I don't believe that's your issue.

[Mouser]

Hm, ok, thanks,

I'm about to take off the right engine cover.
Will see the rest tomorrow.

Thanks
Mouser

[Mouser]

Had the cover off, everything seems ok and turns well!

hmmmm,

Maybe it was the head gasket finally then??
If the carb level cannot be the issue
Will put everything together next week and try out.

I'll report!

Thanks
Mouser

[Luders]

Before you put it back together, please just check the head is completely flat and not warped.

In my experience, these heads are prone to warpage and cause such overheating issues.

Stick the side of a steel rule across the face of the head and hold it up side on to the light and check the rule is touching the mating surfaces of the head.

[Mouser]

Sorry Luders, read your post only I put all together already.
Didn't even think to see if it's even, jesus!

After all, I checked the pump, the pump drive, everything seems normal!
I put everyhting back together with a new head gasket.

Did a test run.
So now after pushing it really hard for 5-10 minutes the temp. rises to a max of 95° cylinder head, 85° cylinder and 85° radiator.
The gauge then is a bit farer than the middle position.

What do you think.

Thanks
Mouser

[Luders]

I'm not used to road KR's, so will leave it to someone else to comment.

I'm setting my new KR up to run between 56-58 degrees to give you a comparison figure.