SERIAL NUMBERS



All BSA twins have the engine number stamped on the drive side crankcase directly below the cylinder barrel joint. Frame numbers usually appear on the left side of the steering head. Ignore any raised numbers, which usually identify castings. From 1965, frame numbers moved to the front engine mounting lug - although on post 1971 frames the headstock was again used.

Engine and frame number sequences are:
Model Year Engine Frame
Rigid A7 1947 XA7-101 XA7-101
Golden Flash 1950 ZA10-101 ZA7S-6001
Star Twin (sprung frame) 1951 AA7S-101 ZA7S-14001
A7 (swinging arm frame) 1954 CA7-101 CA7-101
Shooting Star 1954 CA7SS-101 CA7-101
A10 (swinging arm frame) 1954 CA10-101 CA7101
Road Rocket 1955 CA10R-601 CA7-7001
Super Rocket 1958 CA10R-6006 FA7-101
A10 1959 DA10-4616 FA7-8522
A7 1960 CA7-7101 GA7-101
Rocket Gold Star 1962 DA10R-5958 GA10-101
Super Rocket 1963 DA10R-8197 GA7-23643
A50 Star Twin 1962 A50-101 A50-101
A65 Star Twin 1962 A65-101 A50-101
Rocket 1964 A65B-101 A50-5501
Royal Star 1966 A50R-101 A50C-101
Thunderbolt 1966 A65T-101 A50C-101
Lightning 1966 A65L-101 A50C-101
Spitfire 1966 A65S-101 A50C-101
Firebird 1968 A65FB- 101

 

Matching engine and frame numbers from 1969 simplified identification. Better still, a two letter code after the model designation pinpointed the month of build and the model year. This is the code:

Letter Month Year Letter Month Year
A January H July 1973
B February J August
C March 1969 K September
D April 1970 N October
E May 1971 P November
G June 1972 X December

The model year usually began in August when production restarted after the summer holidays. This allowed time for stocks of complete machines to be built up before the new season's models were launched at the autumn Motorcycle Show.
Example: Matching engine and frame numbers A65T-BD04887, identify a Thunderbolt (A65T) built in February (B) of the 1970 (D) model year.