Before Break in

Writing about engines are so difficult for me.
Please comment me about wrong English composition.

Break in is most important thing of nitro engines life.
Why it is so?

RC nitro engines don't have piston ring.
Piston fits sleeve directly.
It cause complex issue.

Piston is heated by combustion.
Sleeve is heated by piston indirectly.
There is gap heating timing.

Then these increase volume by thermal expansion.
Like I told another story.
Thermal expansion is not uniformity.
And each material has each thermal expansion rate.

line expansion rate
Aluminum(piston)　             :　23.1
Brass(sleeve)                    :  17.5
Chromium(sleeve surface)   :    6.8

So sleeve resist thermal expansion.
Piston expand easily.

Brake in compromise different material fitting under racing environment.

Before break in, we have to check each parts.
Is there burr,failure of manufacture?
For example My engines these are...

This is a failure of hardening on out of box.
Like a DNX8 shock shaft.

 There are burrs.

Almost engines have something wrong.

Manufacture can't pay for the cost of QC.

I understand we can't buy engine that take completely QC for $300.

RC engine is a engine.

I can't find all these issues.

Burrs,miss match sleeve to engine block,misalignment pin boss etc...

I usually order engine initiation service by NEXT.

NEXT is a Japanese engine tune pro shop.

I usually order MOS hardening service too.

Totally I pay for the QC about $100.
I pay for feel ease before break in.
If there was burr,I have to pay more yens after break in.