There is no temp sensors that I am aware of that allow monitoring in the ground station. Plenty of them available for RC telemetry.
A free-air-cooled two-stroke engine at full load can hit 450F cylinder head temperature, which is about 230C. RC format fan-cooled engines normally don’t run that hot - more in the range of 250-350F.
There is not a good selection of sensors, with appropriately heat-shielded cables to measure temperatures in that range. So I measure the temp on fan-cooled RC format helicopter engines with a sensor on the base of the cylinder near the exhaust port. Normal operating temps measured there are about the same as automotive engines - 165-180F. At 200F the alarm sounds in my RC radio and warns of engine overheat. This usually happens in extended hovering. So when the overheat alarm goes off I either land it, or get it into flight so it can cool down. From an overheat in hover, the simple act of getting the helicopter into forward flight at >20kts cools it down to 180 in only ~3 minutes. The engine isn’t working as hard in forward flight as it is in hover.
So, depending on where you measure the temperature, and the conditions you measure it under, 120C (250F) may not be out of range.