My 1970 BSA Victor is equipped with a chain oiler that is fed from the crankcase. Believe it or not, the oiler is now the only source of leaking oil on this very clean bike. Like the oiler found on my Norton, I would like to disable it and clean and lubricate the chain manually. Has anyone done this? Is it straightforward? Is this a bad idea?

Yes, it's a good idea to block it. You can use all matter of screws and clamps but the right way is to JB weld the .040 inside the primaty cover. To do this, take out the clutch basket. Winter job.