Sport_Pilot,

I meant this "four cycle forbiding" only about the break-in period (although R/Ciers do tend to forget other fields of aeromodeling...).
I corrected it both in the original article and in my reply to you.

Thanks for the comment.

And yes, break-in does remove some material from the piston crown. But as long as some interference can be detected when the engine is cold, the clearence is small enough not to allow varnish build up, even in normal running temperature.

This method will give you the best results, engine life, reliability, easy starting...

Sincerely,