I gave up trying to understand the haphazard way in which BSA delivered the change over to unified fasteners. The 5/16" rocker cover studs are unified, but the 1/4" are CEI, on the same head casting!?!
I own a 69/70 t120. about 60/40% unified / imperial.
If you think beezer make a hash of going UNF
, have a look at triumphs....... they were completely crap at the job.
The factories just used up stuff they had and moved to unified as they went. Not rocket science. Norton still used BSF
years later. If they had received orders at the beginning of the year for total production runs, it would have been worth
changing in one go, but they didn't. Like using imperial sized bearings, why didn't they go metric?