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BSA Serial Numbers

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B Single - B31 & B33

Year   B31 Engine   B33 Engine

1946   XB31-101       XB31-101
1947   XB31-101       XB33-101
1948   YB31-101       YB33-101
1949   ZB31-101       ZB33-101
1950   ZB31-9001     ZB33-4001
1951   ZB31-15001   ZB33-7001
1952   ZB31-21001   ZB33-11001
1953   BB31-101       BB33-101
1954   BB31-6001     BB33-2001
1955   BB31-15001   BB33-5001
1956   BB31-22001   BB33-7301
1957   BB31-             BB33-
1958   GB31-101       GB33-101
1959   GB31-1909     GB33-662
1960                           GB33-1001

Year   Rigid Frame   Spring Frame

1946
1947   XB31-101
1948   YB31-101
1949   ZB31-101        ZB31S-101
1950   ZB31-9001      ZB31S-5001
1951   ZB31-14001   ZB31S-10001
1952   ZB31-19001   ZB31S-17001
1953   BB31-101       BB31S-101
1954   BB31-1386     BB31S-5895
                                  CB31-101
1955                          BB31S-12001
                                  CB31-6001
1956                          EB31-101
1957                          EB31-
1958                          FB31-101
1959                          FB31-2572
1960                          GB33-101



A Unit Twins, 1962-65

Model  1962 Eng./Frame

A50      A50-101/A50-101
A65      A65-101/A50-101

Model  1963 Eng./Frame

A50      A50-823/A50-2288
A65      A65-1947/A50-2288

Model          1964 Eng./Frame

A50               A50A-101/A50-5501
A50 (Police) A50AP-101/A50-5501
A50C (USA) A50B-101/A50B-101
A65               A65A-101/A50-5501
A65 (Police) A65AP-101/A50-5501
A65R            A65B-101/A50-5501
A65R (Tach) A65C-101/A50-5501
A65T/R         A65B-101/A50-5501
A65L/R         A65D-101/A50B-101
A65SH          A65E-101/A50B-101

Model          1965 Eng./Frame

A50               A50A-686/A50-8437
A50 (Police) A50AP-121/A50-8437
A50C (US) A50D-101/A50B-4001
A50CC (US) A50B-507/A50B-4001
A50C (UK) A50DC-101/A50B-4001
A50CC(UK)A50DC-101/A50B-4001
A65               A65A-1134/A50-8437
A65 (Police) A65AP-267/A50-8437
A65R            A65B-334/A50-8437
A65R (Tach) A65C-1082/A50-8437
A65L/R       A65D-1742/A50B-4001
A65SH          A65E-701/A50B-4001
A65L        A65DC-2158/A50B-4001
A65LC     A65DC-2158/A50B-4001


A Unit Twins, 1966-69

1966                            Engine

A50 Royal Star        A50R-101
A50 Wasp                A50W-101
A65 Thunderbolt     A65T-101
A65 Lightning         A65L-101
A65 Hornet              A65H-101
A65 Spitfire             A65S-101
Frame No. - All        A50C-101

1967                    Eng. & Frame

A50 Royal Star        A50RA-101
A50 Wasp                A50WA-101
A65 Thunderbolt     A65TA-101
A65 Lightning         A65LA-101
A65 Hornet              A65HA-101
A65 Spitfire             A65SA-101

1968                    Eng. & Frame

A50 Royal Star        A50RB-101
A50 Wasp                A50WB-101
A65 Thunderbolt     A65TB-101
A65 Lightning         A65LB-101
A65 Firebird            A65FB-101
A65 Spitfire             A65SB-101

1969                    Eng. & Frame

A50 Royal Star        A50RC-101
A65 Thunderbolt     A65TC-101
A65 Lightning         A65LC-101
A65 Firebird            A65FC-101


Models 1969 On

The engine number is located on the left side of the engine, immediately below the cylinder barrel flange. The number is stamped onto a raised pad. The frame number is located for BSA's 1969 and earlier on the left side of the frame, on the front engine mounting lug. BSA's 1971 and later, either side of the frame on the stearing head to frame gusset, note that these don't always have the model stamped. On'71 up, 250-500 single oil in frame bikes, the number is located on the kickstand lug or steering head area on late bikes. The Number consists of 4 sections.

The first letter indicates
the month of manufacture.

A = January
B = February
C = March
D = April
E = May
G = June
H = July
J = August
K = September
N = October
P = November
X = December

The second letter indicates
the year of manufacture.

C = 1969
D = 1970
E = 1971
G = 1972
H = 1973

The third section is a numerical block of five figures which commence with engine number 00100.
The fourth section indicates the model. I have seen this section placed first on the pad as well.


Example

Month  Year  Number    Model
N            D       00100       A65T

Example 2

Model    Month  Year  Number
A65T      N          D       00100