guys are correct you dont want to lean out teh motor too much and run it a bit rich as you run it in.
In the same breath though you dont want the engine overly rich as you will accellerate wear.
Best is to get teh engine up to temp and then let it cool down for 10/15 mins and repeat so you heat cycle the components.
The tune for decent performance and keep it a touch rich with a nice smoke plume from the pipe.
After a while you will notice the motor starting to feel better and it will also start running a bit cooler.
The temp gauge is a guide and not exact temp the motor is running at.
On most temp gauges it will be in the ball park but note that different colored heat sinks will give different readings.
I use the temp gauge in conjunction with the spit method and also noting smoke and performance.