Thanks marthy, this was an interesting read even though it was based on cars but the principle is the same, Engine - Breather System - Tuning Guides , the idea of having the crank vent to atmos means that there is no oil vapour getting into the air system and ultimately gumming it up (epa laws...
Marthy I've got a stock motor but running a two brothers exhaust, I've ordered a PCV and some block off plates, I also just today blocked off the crank case ventilation with a small pod filter and plugged the air box inlet, I have two questions after reading this thread, if I have no O2 sensor...