I use a tiny tach tachometer made by echo, has a very fast refresh rate and can replace the internal battery by removing some small screws on the rear of the unit, (some tachs do not allow for internal battery replacement) cost about $50 BUT
to get to the bottom line of a chainsaw overheating and seizing, NOTICE that I did not mention carb being adjusted lean because other things can cause overheating and seizing I started using a 3M infrared thermometer and monitoring the jug temperature while the saw is into a heavy full bar cut with a sharp chain.
I first use the tach and set the carb H jet so as the saw is 4 cycling slightly rich and not over reving on the tach, then take the 3M and the saw to a large log for a full bar cut load test and load the saw full bar with a sharp chain and monitor the saws jug temperature. If all is well the temp will not exceed around 375 degrees, if it starts getting to 400 and doing so fast the block/piston is overheating and the saw is going to sieze due to the piston swelling and scrubbing. A helper is handy for aiming the thermometer while saw is in a full bar cut with a downed log but if chain is sharp the saw will load itself and helper not required.
Might not be a carb adjustment, might be fins clogged, seals leaking, carb leaning out due to other things.
You can also adjust the carb H jet to lean and load the saw and see the temp rise fast and the engine is below factory rpm specs when in the cut. (overheating due to running lean, but not exceeding spec'ed max) rpms in the cut.
excess Mixed gas (rich) hitting the piston is what is keeping the piston from overheating.
Anyway: The infrared thermometer lets you know that things are not going well immediately BEFORE the meltdown and a tachometer won't always let you know. Just because the engine is not overrevving (rpm's too high) does not really mean that it's not overheating or going to eventually overheat and the infrared gives you an immediate heads up that temp is headed for the critical zone.
I'm constantly reaching for the 3M doing heat/AC tests and checking cylinder exhaust temp tests on Auto engines to see if the cylinders are balanced and confirming engine block temps.