100C? Isn't that boiling (sorry, I live in prehistoric times where we use some system that makes no sense at all)?

I would say you don't want it that hot. I know at anything above 65-70 I would be thinking I needed more air or risk damage.

I would also question the concept of adding Injection Jet cleaner to the fuel. Not sure how that will "mix" with 2-stroke oil (or not). Probably better off pulling the carbs out, making sure nothing has blocked up the jets and go from there.

As for the overheating, I would suggest draining the coolant and checking the thermostat to make sure it's operating properly and allowing coolant to flow through the system.