Ugh Dave, for over a decade I've read the reports of sludge'd cranks w/o filter later being found clean inside when filter used. Yet on anal oil care on Ms Peel I saw 1/16" sludge layer at 7000 miles and on Trixie that came with decades mounted filter about 1/8" layer and then some accumulation with new crank and filter at ~1000 miles then again at ~300 miles. Slotted pistons inside Al gasket got Trixie first time, then rod bolt the second time. I like filter idea but lost faith in them to do as much as advertised unless with a special fine filter that hardly no one installs. Ms Peel has the option to put in 10 micron filter element but now doubt it'd do much but add pumping losses to Peel. We read about those pleased with long term use of the bottom of the filter feeding brands Framm, which I take to mean even the poorest filter does as well as the best mass market filter, which implies to me filters are not that important to get concerned about in Norton engines. Magnets only catch the ferric elements, not Al-oxide-sapphire, brass, copper, carbon grit, who ratio's of production can be monitored in sludge samples, which I find about 1/3 is magnetic, 2/3's missed by filter ain't.
I'll ask Wes what he found on his seized by age 50k+mile crank trap before he installed a filter mount i gave him off Peel. I did not find much sludge in the several crank cheeks I got from rather used, likely -sans filtering era- stock piles from Baxter's or Waldridge or ebay.
So my reality check to rearrange my mind on this is - Are the Norton experts more informed or mis-lead than the fleet managers, tribology references and hobot?