Back in the 60's diesels up to .15 (or 2.5cc) rarely had problems other than to those who didn't like the smell. At the time we thought bigger engines like 3.5cc upwards would not be very suitable due to the vibrations that came with increased size. The really big engines that came to use later on, often with a piston ring, is yet another matter.
So for smaller CL engines, I think diesels are really good fun. No carbon problems that I know of. The combat and team race diesel powered models have shown us how powerful these little engines can be.
Maybe the diesel concept is best suited for the smaller engines?