Jim,

converting is no problem, point of measuring isn't the same.
I read a temperature you did measure of 234 F is 113 C and I measure always above 150 degrees C.

You write:
Sensor is against the cyl wall, between the two largest cooling fins, on the back side of the engine.

Jezmo does show us the absoluut max temp of 200 degrees, and that has to be a contact temperature on the basic, or washer/sealring of the sparkplug. (I think?)
For me also there is one place to use, the glowplug seal ring.
Also for glowplug engines the temperature is between 160 and 180 degrees C , and I became nervous above 180!
My proposal would be, only compare contact temperatures of basics of spark or glowplug.
There are two elements Pt100/500/1000 or thermouple to use for that (I think), thermocouple is more rigid and better to install and so often used.


Cees