I was kinda wondering if temperatures under load are a better tuning indicator than rpms or sound? Agree not very practical for permanent mounting, and would be slower tuning than using a tach or trained ear.
It's been my experience that using the IR temp indicator is not slower. It will start detecting a runway heat condition
real fast when the saw is buried in wood and loaded. The temp will head towards 400 F real fast if running lean or the piston is already scrubbing, etc. From experience testing saws a normal temp gets to around 350 slow and max of 375 slow not exceeding 375. On a normal saw you can adjust the H jet lean and bury the saw in wood and the rpm's remain below max spec'ed under load and the saw will start overheating real fast.
This has been my experience and why I always use the IR temp check on my saws before calling them ok to go to the wood lot.
I have a 24 inch downed white pine log handy for doing the IR tests.
I thought of this IR testing sometime back when I had a old 028 stihl seize up in a full bar cut and had been running ok for years. I checked some other saws including Stihls, Homelites, Poulans and some old McCullochs with the IRT (so as to get a average temp of the jug when in a full bar cut) and seen them staying below or around 350F then when I buried the 028 that had seized. (the siezed 028 re-started after a long cool down) I immediately seen it headed for 400F fast and a meltdown using the IRT. I pulled the muffler and all still looked ok and I adjusted the H jet out about 1/2t for a 4 cycling and all ok on the IRT. The tach was at the max unloaded rpms piss reving the saw and it was not 4 cycling. The rpms were less than spec in the cut loaded during overheat, but the engine was running lean. The saw stayed cool when I adjusted H jet for the 4 cycle sound and would immediately start overheating if I went back towards the original carb H jet setting in the full bar cuts.
I went ahead and pulled the carb and installed a kit, checked the fuel lines and filter, did a leak test of the block and she is still doing great today. (something changed to make the saw start running leaner is why I went to the carb kit and inspected other things and the IRT confirmed afterwards and eased my mind that it is not overheating after doing maintenance adjustments)
I use a tach and do the 4 cycle adjustment during preliminary tuning and then confirm the final temp test with the IR thermometer.