Break in of a fresh engine
A piston ring is seated in the first few seconds of engine running after its installation. This holds from the smallest to the largest of ringed engines, and is dependent on cylinder pressure to force the ring against the bore. Therefore, the initial running should be done at a high power setting.

My way is to allow the engine a few seconds to come up in temperature, then I immediately peak the mixture at full throttle, then right back to idle. For the first few minutes of running the engine goes to full throttle for about five seconds, then back to a rich idle for twenty. This gives me the high cylinder pressure to seat the ring while at full, and then at idle more oil is spread on the working parts.

After these first few minutes I'll go back to full and get about 800 rpm rich drop, then lean the idle a bit but not all the way, and put the engine in a plane. Over the next hour or two I'll slowly lean the idle, and bring the HS closer to peak. After a couple hours total time the engine is all ready for extended high power, and I've been able to fly the fuel through the engine instead of oiling the grass at my house. Or not oiling the grass as much as many do.