My K1100lt stays just at the edge of the red for temp.
Where should my gauge be staying while riding? At the edge of red even during cool mornings.

Not really, i would expect it to be mid green. ideally. you dont say if fan kicks in or temp light comes on so i would check coolant mix, test thermostat, just to be sure.
PS worth testing temp gauge as well

Fan does come on, no temp light. I just don't remember
seeing it run this hot. Is there an ohm test for the gauge?

On my bikes, the BMW temperature gauge needle stays around the 11 o'clock position when moving.  When stuck in traffic it will go to the 1 o'clock position.  About half way from there to the red the fan will come on and the temperature will come down to the needle at the 12 o'clock position.

If your gauge is reading high, are you sure the engine isn't overheating.  The cooling system on K bikes can be a little marginal in hot weather.  If the passages in the radiator are coated with mineral deposits from a previous owner who filled the system with well water or the fins are full of bugs, the radiator's cooling efficiency will be reduced.  It's also possible that the thermostat isn't fully closing off the radiator bypass when the engine comes up to operating temperature.

Two years ago I replaced the thermostat and coolant. Just as a preventative.

Might be a good idea to do a cooling system flush ,and ditto on #4 with cleaning bugs out.
One other thing , Check the hose from RAD to HEADER TANK for blockage or kinks

Thanks for the replies.
Summer has kept me to busy for trouble shooting.
I did ride through a rain storm last week and the temp dropped quickly below to halfway mark.
I will start with flushing the system and check the hoses.
Thanks

Just remember that the sensor for the temperature gauge is under the water pump and only serves the gauge and nothing else.

The cooling fan and temperature warning light are fed from the temperature sensor behind the radiator which also feeds into the Motronic unit. This one appears to be working properly as fan comes on and red warning light does not. It only comes on if the engine over heats.

The fan comes on when the temp of the coolant coming out of the cylinder head reaches 105C (221F).

The temp warm lamp illuminates at 115C(239F).

If you keep riding and the temp reaches 120C(248F) then the radiator cap will blow (just like an overheating car.)  It gets on your left foot.

It is rumored that the Motronic will shut down somewhere above 120C but I've never felt that risking destroying engine was worth it to to test that.

I finally was able to take the thermostat out and tested it also checked radiator it was clean. Thermostat is working properly so I reinstalled it and put bike back together and have been using it without the bike running hot. Temp gauge gets to the half way point and fluctuates up and down slightly. Before the temp would slowly get higher until it reached the red zone where i would pull over and sit awhile.
Warm days are back here in beautiful sunny Florida so we will see if my bike starts to run hot again.
Thanks for all of the input.

I never look at the temp gauge on my K bikes.

Why? Three reasons:

1 - Looking at it will never change the coolant temperature.

2 - If I'm worrying about that and watching the temp gauge then it decreases my situational awareness.

3 - As long as the idiot light in the cluster does not come on then there is no cause for concern.

JM.02

diveshadow wrote:I finally was able to take the thermostat out and tested it also checked radiator it was clean. Thermostat is working properly so I reinstalled it and put bike back together and have been using it without the bike running hot. Temp gauge gets to the half way point and fluctuates up and down slightly. Before the temp would slowly get higher until it reached the red zone where i would pull over and sit awhile.
Warm days are back here in beautiful sunny Florida so we will see if my bike starts to run hot again.
Thanks for all of the input.

I presume it heats up much quicker if you are going up a steep grade, if so does it cool down quickly when you go down or does it remain hot or maybe very slowly cool a bit. If it is slow cooling as I expect the answer is then you have a very compromised cooling system, the usual culprit is the radiator being blocked internally.
Solution is to get a good one as they are close to impossible to clean well.

Rick G wrote:I presume it heats up much quicker if you are going up a steep grade . . .

diveshadow wrote:Warm days are back here in beautiful sunny Florida so we will see if my bike starts to run hot again.

Although diveshadow undoubtedly is a traveler, the highest of high points in sunny Florida—where his Brick allegedly overheats—is Britten Hill at 345 feet, unless Daytona Beach and South Beach during spring break are included.  

ds's Brick's gauge could be faulty but if ds can't shed this obsession any other way, the Brick might benefit from the installation of a Spal puller fan like the ones described in these threads.

+1 on Laitch's topographical comment. 

It sounds like the bike might have had a thermostat that was allowing flow through the bypass after the engine warmed up.  This reduces flow through the radiator and the cooling capacity of the system.  I used to work in a boatyard and had to deal with a similar problem on old Atomic Four sailboat engines. 

The thermostat not only opens to allow flow through the radiator, but also must block the radiator bypass.  If the bypass is not blocked the engine in a K bike is guaranteed to run hot, especially in warm places like Flordia.  The thermostat must not only need to work properly, but it must be installed correctly to control the flow.

Another thing that can lead to running hot is cooling fins on the radiator being plugged with the mummified remains of thousands of miles of bugs and cottonwood seeds collected over the years.  One of my 4 valve K100's had the fins clogged almost solid with enough bugs to feed a family of four.  A good overnight soak both internal and external with white vinegar followed by a good rinse cleaned the radiator inside and out, restoring the proper cooling operation.

Has the bike ever actually had the cluster idiot light come on?

Thanks for all of the input.
I took the thermostat out and tested it.
It worked correctly so I installed it back in and put the bike back together.
The bike is staying in the middle of the gauge for now. Rode the bike through out the summer and no problems.
And yes there are no steep grades in Sunny Florida.