coolant won't make that much of a temp diff ,just the boiling point raises (as does the psi,from the cap)....
they have air flow issues if your moving pretty good (& not behind alot of other bikes ,making heat), 160-180... doing doughnuts or slow trails it'll jump to 220 verry quick... the best thing is A temp gun (the prices have come way down) but just go to the local hardware store & get A T put it in the line from head output back to rad hose & put your choice of gauges w/ mech sender on.