Related question:
As fitted at the factory, the breather tube, A51S leads downwards via a banjo, to a tube A52/2AS, and through a hole in the RH front engine plate, where, on M018 it appears to stop an inch later. The whole thing can't be much more than a foot long. Here's the question: is that true? The factory-fitted breather stopped just behind the front engine plate?
Because if it were made long enough (as suggested in KTB for instance) to reach the back of the bicycle, then the resistance to flow would be MUCH greater. If it were now a four foot run, the resistance would be four times greater. The result might be a breather that was largely ineffective, even when the slot was opened out to the max. Like mine was.
The underlying puzzle I'm trying to solve is: why are breather improvements such a talking point? Is it because owners have disabled the design by extending the pipe? Because if that IS true (Lindie...) it would explain why so many motors seem to take an easier route and breathe through the dynamo.
But there must have been a time when breathers worked. It was after all Phil Irving who designed the motor, and PEI was no fool. Anyone adept with a Ouija board would do us all a great service by asking him...
Opening up the tube ID would counterbalance increased length, so civilisation might in fact, yet be saved. My 1960-ish (WVA793, where are you now?) Ducati 175 had an open (untimed) breather about 2 foot long, that was 5/8" ID, roughly 3 x the cross-sectional area of the Vincent breather. Did Ducati know something?
(Such calculations are an essential part of the engineering for drilling oil wells: make the pipe long enough, and small enough bore, and drilling fluid will never reach the bit, fa less flush the cuttings back to surface. So there is a bit of elementary science behind this.)