Here is one answer, of the best: WHERE DO SYNTHETICS EXCEL?. It has all the high pressure properties you need for a motorcycle oil plus the heat stability.
While these new standards may be good for your new passenger car, it is not good for your vintage motorcycle. Triumph motorcycles along with other flat tappet .
My bike is currently running very well however when I pull the clutch in from cold there is a hell of a clunk and sometimes it's stalls the bike .