26 and 35cc steel liner; 45cc nicasil barrel. Rotax has nikasil barrels.
The steel liners will show a slightly lower cylinder temperature, but that is it.
Should an engine sag in the test, power is shut down immediately and the carb reset, just like you do. Power loss is a lean mixture telltale. A well tuned carb will climb up to best rpm as the engine heats up.
That is what I would call fully leaned out. Tuned like that, the engine will scream in a dive, and never enter a four-stroking pace unless throttle is reduced. A richer mixture will four-stroke when in a dive, and still burn the plug clean. This is about the range I used for my temperature measurements.