[Diesel_Dave]

I think what your describing is actually called the Miller cycle rather than the Atikinson Cycle. Both have the same basic goal: expansion ration > compression ratio, however, my understanding is that the Atkinson cycle actually uses a different conrod/crank mechanism, whereas the Miller cycle uses the conventional conrod/crank and just adjusts the intake valve closing (IVC). Changing just the IVC, however, won't give you any benefit. The benefit would come from running a high compression ratio piston that would otherwise knock.

On another note, I've toyed with the idea of finding a motorcycle with a blown engine and putting a small diesel on it. Just a thought...