Tuning by temperature depends on alot of variables. Temp Guns as well. I have seen temp swings of 40 degrees F between guns. Also the method on how someone temps it is another factor. I use an Exergen 501, and try and temp it the same way each time. I make sure the cone is perpendicular to the head entering the cooling head.

If you use a temp gun.........use the same one each time. It will help you gauge a baseline reading on that motor.........and that particular day's ambient temps. For mains, you might want to start the motor a tad rich. Perhaps an hour or two richer on the top end. Many motors will come in 20 to 30 degrees hotter after ten to fifteen minutes of hard running. If your on the threshhold of too lean before a main........you might come in overlean during the main.

I know this topic was about specific temp...........but some motors run great at 240...........some won't even get out of there own way unless at 280(.12's that is). Depends on the motor.