BSA Serial Numbers

BSA Motorcycle Logo

B Single - B31 & B33

 Year		B31 Engine		B33 Engine		Rigid Frame		Spring Frame
 1946		XB31-101	 	XB31-101	 
 1947		XB31-101		XB33-101		XB31-101	 
 1948		YB31-101		YB33-101		YB31-101	 
 1949		ZB31-101		ZB33-101		ZB31-101		ZB31S-101
 1950		ZB31-9001		ZB33-4001		ZB31-9001		ZB31S-5001
 1951		ZB31-15001		ZB33-7001		ZB31-14001		ZB31S-10001
 1952		ZB31-21001		ZB33-11001		ZB31-19001		ZB31S-17001
 1953		BB31-101		BB33-101		BB31-101		BB31S-101
 1954		BB31-6001		BB33-2001		BB31-1386		BB31S-5895
		BB31-6001		BB33-2001	 				CB31-101
 1955		BB31-15001		BB33-5001	 				BB31S-12001
		BB31-15001		BB33-5001	 				CB31-6001
 1956		BB31-22001		BB33-7301	 				EB31-101
 1957		BB31-			BB33-	 					EB31-
 1958		GB31-101		GB33-101	 				FB31-101
 1959		GB31-1909		GB33-662	 				FB31-2572
 1960	 				GB33-1001	 				GB33-101

A Unit Twins, 1962-65

			1962 Eng./Frame    1963 Eng./Frame    1964 Eng./Frame    1965 Eng./Frame
A50	 		A50-101/A50-101    A50-823/A50-2288   A50A-101/A50-5501  A50A-686/A50-8437
A50 (Police)	 	 		                      A50AP-101/A50-5501 A50AP-121/A50-8437
A50C (USA)			                              A50B-101/A50B-101  A50D-101/A50B-4001
A50CC (USA)			                                                 A50B-507/A50B-4001
A50C & A50CC (UK)			                                         A50DC-101/A50B-4001
A65			A65-101/A50-101    A65-1947/A50-2288  A65A-101/A50-5501  A65A-1134/A50-8437
A65 (Police)				                      A65AP-101/A50-5501 A65AP-267/A50-8437
A65R				                              A65B-101/A50-5501  A65B-334/A50-8437
A65R (Rev counter)			                      A65C-101/A50-5501  A65C-1082/A50-8437
A65T/R				                              A65B-101/A50-5501	 
A65L/R				                              A65D-101/A50B-101  A65D-1742/A50B-4001
A65SH				                              A65E-101/A50B-101  A65E-701/A50B-4001
A65L & A65LC				                                         A65DC-2158/A50B-4001

A Unit Twins, 1966-69

			1966 Engine    1967 Eng. & Frame    1968 Eng. & Frame    1969 Eng. & Frame
A50 Royal Star		 A50R-101	A50RA-101	     A50RB-101            A50RC-101
A50 Wasp		 A50W-101	A50WA-101            A50WB-101	 
A65 Thunderbolt		 A65T-101	A65TA-101	     A65TB-101            A65TC-101
A65 Lightning		 A65L-101	A65LA-101	     A65LB-101            A65LC-101
A65 Hornet		 A65H-101	A65HA-101	 	 
A65 Firebird		 		                     A65FB-101            A65FC-101
A65 Spitfire		 A65S-101	A65SA-101	     A65SB-101	 
Frame No. - All		 A50C-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 second letter indicates
the month of manufacture.     the year of manufacture.

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

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.


Month 	Year 	Number 	Model
N 	D 	00100 	A65T

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