B31 numbers

[Dennis49]

How all I have just bought a 1950 B31
The original buff log book shows different engine and frame numbers.
Be gentle with me as this is my first forum post.
Should the numbers match?
Dennis

[JulianS]

For 1950 both engine and frame should start ZB. It is unlikely that the following numbers would be the same.

[Dennis49]

Thanks for the clarification, I often see matching numbers bikes for sale and it just gets me wondering....

[JulianS]

Match number usually mean that the numbers are the same as when the bike left the factory.

About the only BSA, pre 1966, to have the same production number for frame and engine would be Army bikes and bikes supplied to the AA.

[Dennis49]

I never knew that!🤥😊

[ducati2242]

have a look here it should explain your numbers .http://classicenglishbikes.com/tech_file/bsa.html