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Thanks, Luddite
What I understand from the article is that the most inefficient engine as far as pumping losses are concerned is a single cylinder. A four-cylinder (or V8), provided the crankcase is unrestricted for movement of pressure within the crankcase has very few pumping losses other than moving the air from one part of the crankcase to the other. A 360-degree twin is essentially the same as a single and a 180-degree twin better but not as good as a four-cylinder.
A 90 degree V twin should be somewhere between the single and the 180-degree twin - towards the single end of the spectrum because of the unequal firing order.
So for maximum bhp efficiency on a V twin, you need the biggest unrestricted breather pipe venting the crankcase to the atmosphere.
You need to stop crud entering the crankcase so the outlet should have some sort of one-way filter and ideally you want to return the oil in suspension with the crankcase pressure exhaust air to be returned to the crankcase. Control of emissions would be a "Californian" (and manufacturer) concern to most legislators but to petrol heads, let's just maximise horsepower. Any oil mist expelled would obviously need to be kept away from the black rubber rings that keep us on two wheels.
If the piston rings are a good fit in the bore and the valve seals are good it sees to be a good plan to de-restrict the breather of reed valves and let the engine breathe rather than wheeze through a 20mm bore pipe/read valve and potentially choke on its own emissions.
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