Duh unless running a special "bypass" filter to catch actual friction size particles all the spin on filters are essentially equivalent as vast majority of auto and trucks and nothing special needed for Nortons and nothing sepecial available either. Spin on filter only filter stuff that could clog oil passage with is not hardly even possible in a Norton, even crank vents to rods have so much flow and sling pressure it'd blow through sludge levels collected in sludge trap. So just google up oil filters list for Commandos and then look up the brands specs or youtube oil filter tests. Fram is at bottom of the lists so avoid them. You could go yrs w/o changing out filters before might collect enough crud to cause bypass valve to function, expect maybe wet sump cold starts, til warmed up some but don't strave engine one iotta. Consider that prior to mid C'do production run, when people had to depend on long term economic use as only transportation, there was no oil filters installed. Sorry but I too got depressed on searching up the false sense of security on oil filters.
BTW NOT GOOD FORM TO POST IN ALL CAPS as comes across as yelling inside our reading minds.
