its always a good idea to find out what the manufacturer recommends on what is a good running temp, this will give you a ball park figure, my picco loves to run at around 105-110c nice and rich and good smoke where as some novas might run a little hotter, but at the end of the day temp is not the issue just a guide as long as you have good smoke(lubrication) use the correct fuel and plug and have good power your engine will run well
cheers