just wondering for you nitro people

[bentz2151]

when you break in an engine what is really happening and why does it stall

[Big-Bus7]

the piston is some how forming to the side of the piston sleeve, creating more compression i believe.

[Mr. Mukai]

Since the parts of the engine are mass produced, they aren't really all perfectly fit to each other. Break in wears all the anomalies into each other, thus creating a completely unique engine in terms of parts fit.

Yes, it does build better compression.

[slash racer]

The break in lets the piston expand and contract through heat cycles. This is very important step and must be done right for performance and motor life.
I let my motor temps get to about 140 f. and let it cool down with the piston at bottom dead center. Most of my motors needed a gallon to break in properly and can up to 9 gallons through them.
Run them rich but not to rich this can hurt a motor too.

[Carbonrevo33]

Yeah, it is lubricating and warming up the piston and all those moving parts. So it is trying to get performance by, in a sense, creating a groove for it to go in and get stronger. I guess it creates a memory?