I think Cynic meant that the sender unit might be faulty.
I don't know much about these bikes however, based on what you have written I would say a faulty sender or temp gauge. 2 different engines with I am assuming 2 different thermostats (if they have those). Rad changed. That really leaves the hoses, temp sender unit or temp gauge. You say that the engine doesn't get that hot, and if it was, you would be able to smell it. Have you checked the hoses are not collapsing under pressure? If this isn't happening then I would guess the sender or gauge are faulty.