I think we have to dispel the misconception that oil from the breather being recycled into the inlet causes loss of power.
It does not.YS engines do it.Oil ratio goes up and you adjust for it..If breather oil is dirty and contains dangerous impurities, then the oil is substandard or the engine has tremendous wear.
If it is the case then YS , OS, ASP, Magnum and full sized engine manufacturers should be sued for poor engineering.In fact the good thing is that residual fuel left over is recombusted and blown out thru the exhaustThere is also no direct opening from the breather into the crankcase to introduce outside air that could cause corrosion, a fact I found in saitos with their rather large breather nipple.
Oil that is not burnt is ejected out thru the muffler. Oil quantity ejected is the same for all engines with the same oil content and tuned properly. Its just that the oil is ejected thru the muffler instead of the breather and muffler.
On a footnote, saito engines left the LS needle purposely rich for running in. It does not effect the topend rpm of the engine if only the HS is adjusted. The topend will suffer if the LS is adjusted later on.A close look at the carb will tell you why.