The A10 however will produce a solid could of smoke that goes 2 or 3 gardens down and lasts for ages. Considering how good a condition the engine is its beyond annoying. It has an oil filter on the return and I'm now wondering if that empties into the engine too.
Blimey! That isn't good, don't blame you for wanting a cure then. Could be as Rex says above, but if, per your original post on this subject, we're talking 1/4 pint in a few days, or 5 fl oz, I'd be amazed if that would be enough to smoke out all the neighbours and take so long to clear. Maybe there is a return-side filter drainage problem . . . but what comes out the bottom will tell you what's dripped in, from wherever.
And there will always, I presume, be some oil in the bottom when it's been standing after a run, as the oil from the top end drains back down, plus some from the crank probably, and some from the timing chest maybe. 1/4 pint wouldn't be far off I don't think . . . If there wasn't
some oil down there, there'd be no quick oil return on start up: there'd be the sort of delay we see after an oil change and full drain-off. (Some other bikes I have hereabouts are
supposed to have about 8 fl oz in the sump . . .)
Good luck with further tests.