If it is a b40 ss the ss will be in the engine numbers IE  B40SS**** . If other it will say B40 , B40P B40B , B40T , etc .

The Rupert Ratio book on singles says the 1964 B40 takes 285cc of gearbox oil . Which is about 1/2 pint . Im sure I read some where that some of the later ones took 170 cc of gear box oil . I think you are trying to put to much in .

have you another coil you could try then .

The only thing left is the coil , which can cause a misfire , or the petrol . My guess would be the coil .

I made my own Eddie Dow type damper rods for my B44 they work quit well but I would try a thicker viscosity oil first .

From the dvla web site https://www.gov.uk/vehicle-registration/new-registrations .

Supporting documents needed for all vehicles
As well as documents to prove your identity, you must also send:

payment for the vehicle tax
the new registration fee of £55, if you have to pay it
a current MOT certificate, if the vehicle is over 3 years old (over 4 years old in Northern Ireland)
a certificate of newness (or declaration of newness for imported vehicles), if the vehicle is new
any documents you have relating to the vehicle, eg build plans if it’s a kit car
an insurance certificate or cover note (if you’re registering the vehicle to an address in Northern Ireland)

Ive just registered my 1956 bsa db 500 . I rang dvla and asked about the mot and was told " if it is mot exempt it is exactly that ". So
BSAOC dating cert .
frame number insurance,
v55/5
HMRC NOVA .
and that was it .
I did get a SGS inspection but that was all over within a week and my v5 came in 10 days .