sludge trap, it was time to clean

[Oldtoys]

3/4 obstructed, it is not a conspiracy theory 

[Triton Thrasher]

It’s a conspiracy theory if it was put there by the Rosicrucians.

[mikeb]

TT that's a seriously obscure cultural reference (I had to goggle it). did those 17th century mystics ride BSAs?

[Greybeard]

3/4 obstructed, it is not a conspiracy theory 

It's soooo good to know that the work involved to get to that point was worth it, eh?

[BSA_54A10]

The oil passage through the crank only need to be bigger than the oil hole in the journal .
I have seen some that had no visible hole yet the engine was running quite happily with no evidence of catastrophic wear .
I have seen a 68 A 65 that could not hold oil pressure below 2000 rpm when hot do better than 80,000 miles without self destructing.
However the new owner who did not change the oil as regularly as Rhett did blew the engine in less than a year and that engine was run on whatever Ford recommended for F 100 truck engines.