There are 149 km on her, was owned by an older retired gentleman, and then a middle aged guy, both rural, so mostly highway miles, the bike is in very good shape overall, the deal who did the inspection could not believe the miles to condition of the bike, looking as good as it does.
My thoughts are with the flush, and stat replacement the problem should be solved, I had no problems at all during the first 10 days of ownership, steady 3 bars, this just started Thursday of last week.
Coolant level is good, and coolant in reserve does heat up, and the fluid level rises when hot, I also have a clamp that leaks slightly when I hit 5 bars, from the pressure of the increased heat this will be replaced during the repair.
I will also clean out the rad of bugs, and correct a few bent fins (not severe, but does not help)
in my eyes all these things, plus the earlier thread I this that exactly matches my conditions
https://www.st-owners.com/forums/showthread.php?89199-ST1300-overheating