Harvey, 180C = 356F, about as hot as I would wish to push an engine. Most of the microlight boys say when you see a reading of 360 to 380, back off the throttle. I do not know what the thinner air does to the temperature if you see what I mean. What thermocouples, and whose CHT gauge are you using please, as that is next on the list for the trike. I think I'm right in saying that grey colour on the plugs is the norm with unleaded fuel, and that you will not get a black exhaust tail pipe. Thanks for the info. ET43