Can't remember if I posted on this before, but maybe last year when I started cleaning up my head, I noticed that under the valve heads, in the inlet ports, around the area of the downstream end of the valve guides, had differing profiles, a bit the same in exhaust side.
I already had a profile gauge, but bought a Dremel and did some 'sculpting/whittling/dental work', to make things even, carved out about 4mm from one area- am yet to know if I made a difference(detrimental).
Thing is it never ran uneven, actually ran priddy sweet, except for the maggie/condenser, by which time I had repaired, the rest of bike had gone faecal, and haven't really ridden it for a long time, but when I saw those uneven profiles, wondered if it was a contributor to the dreaded 'bias' that it seems can't quite be otherwise defined..?
Open to comment, and hopefully soon (before the end of the year) will have a road test.
Cheers duTch