RE: when you tune what you tune first? REPOST
Like Massive said, with this to add to it.
For an initial tune on a fresh engine, start it up and lean out high speed needle from the factory settings so it is running clean, make some laps to warm it up good. Do not run it too lean and do not run it too rich, crisp and clean, not too lean
Now for a seasoned engine (has more than two or three tanks through it), Fire it up and get it to operating temps with a hot lap or two then adjust the high speed needle till it will not pick up any more power. If you have leaned too much it will sag a little at wide open throttle. Once you get maximum performance, richen the needle just a bit till the performance is still there but it is a little further away from lean.
Now we set the low speed needle for crisp off-idle response and crisp acceleration up to about half to 2/3 throttle. If low speed needle is too rich, it will take a while to clean out and not sound smooth. If it is too lean, it will bog or sag somewhere off idle and feel like it is trying to catch its breath. never try setting lsn or hsn with a cold engine, it must be at operating temp.
No where did I mention use of a temp gun, it is simply not needed. If you want to ruin your engine, start chasing the needles for some magical number. And most importantly do not let any of your friends tell you what temp you should be running at. Just run it where it will be happy and it will last a long time.
Let the flames begin.