Rcpilot,

90 % damage to an engine occurs as a result of starting friction ( Taking the assumption that the engine is not run lean or overheated by over proping) when the engine is not wet with fuel.
I wish we had a lube for R/c engines which had polarized molecules to reduce this wear.

Once an engine is running a very thin film of lube 0.05 Micron Ra builds between the cylinder and the piston even though it is taper bore. This type of Lubrication is called Boundary Layer Lubriction.This protective layer consists of not only Lubricant but also methnol and is there as long as engine is running. In four stroke regime a lot of fuel comes from the exhaust in raw form along just fulfilling this duty.

In a running engine assume the piston speed is 10 m/s at this speed if there is no boundary layer lubrication than the metal may wear in micro seconds

A scientific approach to establish something concrete would be to check the compression with the compression guage with two test sample engines; lets say 61 FX`s.One broken-in in 4-stroke regime and the other at higher running speed each using same fule an prop broken-in with 2-litres of fuel and then checking the Compression of each engine.

I assume that the compression ratio in 61 FX would be about 10:1 or so.

Khizer