I have a similar problem on my formula 125. I have noticed a power loss if the speed is held with the temperature in the red and I assume that the egine is tightening up and the high temperature reading is significant. I am going to take the thermostat out of the cooling system to check and also check the condition of the water pump drive. There is an associated rattle from the area of the water pump that may be part of the problem.
I really like the bike and would be interested in any info on problems and solutions, such as what is the best cure for the seizure of the steering column bushes.