As far as carbon buildup, you have this fuel staring out as a solid/liquid/gas component: locked in suspension you cannot create or destroy those 3 in that environment. See how it returned to a solid is the carbon? What becomes cleaned is more the spark plug. That carbon is melting on the parts inside the cylinder chamber. You don't see granny redline the caddy every weekend running with the canyon riders, right? So that carbon crap is a myth unless you are so jetted rich, you wet the plug instead and it misfires on the top.
What you want is less heat buildup, less strain or excess expansion with tight, new parts. You have this embedding or peening process going on. The piston skirts smack on one side and smack on the opposite side as it moves from the up, then down position(s). There is the crank coming around and that pounds the rod inserts and crank inserts as they move from one stop stroke to the next stopped stroke is that up and down, side to side slapping and stroking down the highway.
You have this 4,000 rpm window. It's fun to quick shift up to 4k, then it's cruise to work under 4k. Is there a wolf pack behind? You lift, snick it down a few gears and wait for them to creep up. You go right back to hammering the throttle up to 4k and if it takes a few more rpm to leave the pack, it's not going to hurt the engine. So, you now eliminate the sustained, and can fluctuate to work is that rpm range. Change gears. Never let it buck in too high a gear, too low an rpm. This more hammers the crank up and down, not runs in a smooth around way is that elimination point.
As is, it won't hurt the hard break-in either. That is to say, it's all about WOT is hard and what is damaging down the road? Hard to say? You could take a survey, see who fills their ram chamber with oil and who does not? Who broke theirs in hard and can match the oily ram chamber and who broke it in book wise and has a dry chamber upon heavy WOT?
Besides the insert hammering, the next break in part is ring seal. There is air being pushed past the rings and that kind of pressure has to neutralize, so it heads out into the closed loop system = Ram Chamber. And we are talking proper oil level, not over filled where it is forced out.
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