A bike that has been unused for longtime need carb. cleaning, fuel line flush out etc.
And the problematic matter: What is the state of the crank sludge trap ?
It it is full , dry and now solid or?
What is the state of the oil pressure reg. valve ?
No one can tell
Starting and running is a huge risk for the "Big ends"
Vintage MC engines need check and investigation before running.
It is 60 years old and a lot of strange "stuff" can and will happen in 60 years of use.
BSA are relativ easy to work on, a robust build bike, but they have there weak spots.
The crank sludge trap and crank oil way in the timing side beeing the to huge weak issues.
Get them checked and sorted, can save disaster...
Apart from that, they can take a lot of use and return a lot of pleassure to the owner.