Taff,
There are bubbles in the liquid in the photos, so I reckon you are probably blowing air through oil galleries in the crank or rod? I haven ever sen a stripped down Berg engine or crank, so its just a guess cos I dont know if there are oil galleries in there.
liquid would prolly be diesel, as you say only diesel or oil, but maybe kerosine - the stuff you buy over here is blue like in the photos, prolly to stop folks drinking it mistaken for water? but I wouldn necissarily want kerro on my crank other than to wash parts.
Azza.