Originally Posted by Mike Rainbird
You have to realise that the geometry (bore and stroke) of different engines means that some will take an increase in compression no problem and there will be good gains to have by this (Eg. Evos), where as others, all this causes is major heat related issues requiring severly retarded ignition (Cossies).
So saying high compression is good or bad is a misnomer, as it is TOTALLY reliant to it's particular engine configuration application.
As Mike has said chamber design and particularly bore diameter has a large part to play in det resistance.
I have dealt with bike engines that can take a bar of boost with a static CR of nearly 11:1.
There are other factors that allow this eg cam timing but it does have a lot to do with their relativly small bore when compared to something like a cossie engine.