It is told the normal crankcase breathing (through gaze filter + extra bore, hollow crankshaft on clutch driving side) is not good enough.
Many bikes are modified buy using a reed valve breather fitted to the oil filler plug of the engine and the advice to block the breather hole in the crankcase.
But I think it will not work, when there is still the hole in the crankshaft.
Do I think wrong?
Michael