Engine and frame numbers
The BSA numbering system has changed quite a few times over the years. As of 1930 a prefix was introduced which referred to the model year. In 1930 the prefix consisted of 2 letters (the first being the year letter), which was reduced to one from 1931 – 1936 (only the year letter). In 1937 the system was changed again. As of model year 1937 the frame used by a group of models got the prefix from the first model in that group for that year e.g. HM19 indicated a 1937 M group model.
Please note that a model year started in September prior to the calendar year and ended in August that same calendar year. E.g. the model year 1936 started in September 1935 and ended in August 1936. These prefixes were often also stamped on parts for the motorcycles for that production year above the Piled Arms stamp. There is no logic in the sequence as you can see from the table below.
1930
| Model | Type | Engine number | Frame number | Remarks |
|---|---|---|---|---|
| A30-2 | 1.74 h.p. | Y… | E… | two stroke |
| B30-3 | 2.49 h.p. S.V | XM.101 | XB.101 | |
| B30-4 | 2.49 h.p. O.H.V. | XR.101 | XB.101 | |
| L30-5 | 3.49 h.p. S.V. | XT.101 | XB.101 | |
| L30-5 | 3.49 h.p. S.V. commercial | XT.101 | XA.101 | Commercial |
| S30-7 | 4.93 h.p. S.V. | XS.101 | XH.101 | Sloper |
| H30-8 | 5.57 h.p. S.V. | XX.101 | XH.101 | Sloper |
| S30-9 | 4.93 h.p. De Luxe S.V. | XX.101 | XH.101 | Sloper |
| H30-10 | 5.57 h.p. S.V. De luxe | XX.101 | XH.101 | Sloper |
| L30-11 | 3.49 h.p. O.H.V | XS.101 | XH.101 | Sloper |
| S30-12 | 4.93 h.p. O.H.V. | XW.101 | XX.101 | Sloper |
| S30-13 | 4.93 h.p. O.H.V. De Luxe | XP.101 | XH.101 | Sloper |
| E30-14 | 7.70 h.p. S.V. V-Twin | XY.101 | XD.101 | V-twin |
| G30-15 | 9.86 h.p. S.V. V-Twin | XY.101 | XD.101 | V-twin |
| G30-16 | 9.86 h.p. W.T. S.V. V-Twin | XZ.101 | XG.101 | V-twin |
| S30-18 | 4.93 h.p. Light S.V. | XU.101 | XL.101 | |
| S30-19 | 4.93 h.p. O.H.V. Light | XU.101 XO.101 | XL.101 |
1931
Model Type Engine number Frame number Remarks B31-1 2.49 h.p. S.V. Y1.101 Y1.101 B31-2 2.49 h.p. O.H.V. Y2.101 Y1.101 B31-3 2.49 h.p. O.H.V. de Luxe Y3.101 Y3.101 L31-4 3.49 h.p. S.V. Y4.101 Y1.101 L31-5 3.49 h.p. S.V. de Luxe Y5.101 Y5.101 L31-6 3.49 h.p. O.H.V. Y6.101 Y5.101 S31-7 3.49 h.p. S.V. Y7.101 Y7.101 Sloper H31-8 5.57 h.p. S.V. Y8.101 Y7.101 Sloper S31-9 4.93 h.p. O.H.V. Y9.101 Y7.101 S31-10 4.93 h.p. O.H.V. de Luxe Y10.101 Y7.101 Sloper E31-11 7.70 h.p. S.V. Y11.101 Y11.101 2 gallon tank V-Twin E31-11 7.70 h.p. S.V. Y11.101 Y11A.101 3 gallon tank V-Twin G31-12 9.86 h.p. S.V. W.T. Y12.101 Y12.101 V-Twin World Tour
1932
Model Type Engine number Frame number Remarks B32-1 2.49 h.p. O.H.V. Z1.101 Z1.101 B32-2 3.49 h.p. S.V. Z2.101 Z1.101 L32-3 3.49 h.p. O.H.V. Special Z3.101 Z3.101 L32-4 3.49 h.p. S.V. de Luxe Z4.101 Z4.101 hand gear change L32-4 3.49 h.p. S.V. de Luxe Z4.101 Z5.101 foot gear change L32-5 3.49 h.p. O.H.V. de Luxe Z5.101 Z4.101 hand gear change L32-5 3.49 h.p. O.H.V. de Luxe Z5.101 Z5.101 foot gear change L32-5 3.49 h.p. O.H.V. Blue Star Z5.101
Z11.1051*Z4.101 hand gear change L32-5 3.49 h.p. O.H.V. Blue Star Z5.101
Z11.1051Z5.101 foot gear change W32-6 4.99 h.p. S.V. Z6.101 Z6.101 hand gear change W32-6 4.99 h.p. S.V. Z6.101 Z7.101 foot gear change W32-7 4.99 h.p. O.H.V. Z7.101 Z6.101 hand gear change W32-7 4.99 h.p. O.H.V. Z7.101 Z7.101 foot gear change W32-7 4.99 h.p. O.H.V. Blue Star Z7.101
Z12.463Z6.101 hand gear change W32-7 4.99 h.p. O.H.V. Blue Star Z7.101
Z12.463**Z7.101 foot gear change S32-8 4.93 h.p. O.H.V. de Luxe Z8.101 Z8.101 Sloper H32-9 5.57 h.p. S.V. de Luxe Z9.101 Z8.101 Sloper G32-10 9.86 h.p. S.V. Z10.101 Z10.101 V-Twin
1933
Model Type Engine number Frame number Remarks X33-0 1.49 h.p. O.H.V. A150-101 A150-101 Only made for the Italian market B33-1 2.49 h.p. S.V. A1-101 A1-101 B33-2 2.49 h.p. O.H.V. S.P. A2-101 A1-101 B33-3 2.49 h.p.O.H.V. Blue Star Junior A3-101 A3L-101 R33-4 3.48 h.p. O.H.V. A4-101 A4-101 R33-5 3.48 h.p. O.H.V. Blue Star A5-101 A4-101 hand gear change R33-5 3.48 h.p. O.H.V. Blue Star A5-101 A5-101 foot gear change W33-6 4.99 h.p. S.V. A6-101 A4-101 W33-7 4.99 h.p. O.H.V. A7-101 A4-101 W33-8 4.99 h.p. O.H.V. Blue Star A8-101 A4-101 hand gear change W33-8 4.99 h.p. O.H.V. Blue Star A8-101 A5-101 foot gear change W33-9 4.99 h.p. O.H.V. Special A9-101 A9R-101 hand gear change W33-9 4.99 h.p. O.H.V. Special A9-101 A9L-101 foot gear change M33-10 5.95 h.p. S.V. de Luxe A10-101 A10-101 Sloper M33-11 5.95 h.p. O.H.V. de Luxe A11-101 A10-101 Sloper G33-12 9.86 h.p. S.V. Light A12-101 A12-101 V-Twin G33-13 9.86 h.p. S.V. W.T. A13-101 A13-101 V-Twin World Tour uitvoering J33-14 4.98 h.p. O.H.V. War Office Twin A14-101 A14-101 War Office V twin
1934
Model Type Engine number Frame number Remarks X34-0 1.49 h.p. O.H.V. B150-101 B1-101 B34-1 2.49 h.p. S.V. B1-101 B1-101 B34-2 2.49 h.p. O.H.V. B2-101 B1-101 B34-3 2.49 h.p. O.H.V. Blue Star B3-101 B3-101 R34-4 3.48 h.p. O.H.V. B4-101 B4-101 R34-5 3.48 h.p. O.H.V. Blue Star B5-101 B4-101 R34-6 3.48 h.p. O.H.V. Special B6-101 B6-101 W34-7 4.99 h.p. S.V. B7-101 B7-101 W34-8 4.99 h.p. O.H.V. B8-101 B4-101 W34-9 4.99 h.p. O.H.V. Blue Star B9-101 B4-101 W34-10 4.99 h.p. O.H.V. Special B10-101 B6-101 J34-11 4.98 h.p. O.H.V. Twin B11-101 B11-101 V-Twin M34-12 5.95 h.p. S.V. de Luxe B12-101 B12-101 Sloper M34-13 5.95 h.p. O.H.V. de Luxe B13-101 B12-101 G34-14 9.86 h.p. S.V. W.T. B14-101 B14-101 V-Twin J34-15 4.98 h.p. O.H.V. War Office Twin B15-101 B15-101 War Office V-twin W34-16 4.99 h.p. O.H.V. Fluid Flywheel B16-101 B16-101 Fluid Flywheel B34-17 2.49 h.p. O.H.V. Sports B17-101 B3-101
1935
Model Type Engine number Frame number Remarks X35-0 1.49 h.p. O.H.V. E0-101 E1-101 B35-1 2.49 h.p. S.V. E1-101 E1-101 B35-2 2.49 h.p. O.H.V. E2-101 E1-101 B35-3 2.49 h.p. O.H.V. de Luxe E3-101 E3-101 R35-4 3.48 h.p. O.H.V. de Luxe E4-101 E3-101 R35-5 3.48 h.p. O.H.V. Blue Star E5-101 E5-101 R35-17 3.48 h.p. Twin Port E5-101 E17-101 W35-6 4.99 h.p. S.V. E6-101 E6-101 W35-7 4.99 h.p. O.H.V. E7-101 E5-101 W35-8 4.99 h.p. O.H.V. Blue Star E8-101 E5-101 W35-9 4.99 h.p. O.H.V. Special E9-101 E9-101 M35-10 5.95 h.p. S.V. E10-101 E10-101 Sloper M35-11 5.95 h.p. O.H.V. E11-101 E10-101 Sloper J35-12 4.98 h.p. O.H.V. Twin E12-101 E12-101 V-Twin G35-14 9.86 h.p. S.V. E14-101 E14-101 V-Twin J35-15 4.98 h.p. O.H.V. War Office Twin E15-101 E15-101 War Office V-Twin
1936
Model Type Engine number Frame number Remarks X-0 1.49 h.p. O.H.V. D0-101 D1-101 B-1 2.49 h.p. S.V. D1-101 D-101 B-2 2.49 h.p. O.H.V. D2-101 D1-101 B-18 2.49 h.p. O.H.V. Light de Luxe D18-101 D1-101 B-3 2.49 h.p. O.H.V. de Luxe D3-101 D3-101 R-4 3.48 h.p. O.H.V. de Luxe D4-101 D3-101 R-19 3.48 h.p. O.H.V. Competition D19-101 D3-101 R17 3.48 h.p. O.H.V. S.P. D17-101 D6-101 W-6 4.99 h.p. S.V. D6-101 D6-101 Q-7 4.96 h.p. O.H.V. D7-101 D6-101 Q-8 4.96 h.p. O.H.V. Empire Star D8-101 D8-101 R-5 3.48 h.p. O.H.V. Empire Star D5-101 D8-101 Q-8 4.96 h.p. O.H.V. Empire Star 3D8-101 D38-1101 mid season change R-5 3.48 h.p. O.H.V. Empire Star 3D5-101 D38-1101 mid season change J-12 4.98 h.p. O.H.V. Twin D12-101 D12-101 V-Twin M-10 5.95 h.p. S.V. D10-101 D10-101 Y-13 7.48 h.p. O.H.V. D13-101 D13-101 V-Twin G-14 9.86 h.p. S.V. D14-101 D14-101 V-Twin R-20 3.48 h.p. O.H.V. New Blue Star D20-101 D6-101 Q-21 4.96 h.p. O.H.V. New Blue Star D21-101 D6-101
1937
Model Type Engine number Frame number Remarks B20 250 c.c. S.V. Tourer HB20-101 HB20-101 B21 250 c.c. O.H.V. Sports HB21-101 HB20-101 B22 250 c.c. O.H.V. Empire Star HB22-101 HB20-101 B23 350 c.c. S.V. Tourer HB23-101 HB20-101 B24 350 c.c. O.H.V. Empire Star HB24-101 HB24-101 B25 350 c.c. O.H.V. Competition HB25-101 HB24-101 B26 350 c.c. O.H.V. Sports HB26-101 HB24-101 M19 350 c.c. O.H.V. de Luxe HM19-101 HM19-101 M20 500 c.c. S.V.Tourer HM20-101 HM19-101 M21 600 c.c. S.V. Tourer HM21-101 HM19-101 M22 500 c.c. O.H.V. Sports HM22-101 HM19-101 M23 500 c.c. O.H.V. Empire Star HM23-101 HM19-101 Y13 750 c.c. O.H.V. Vee Twin HY13-101 HY13-101 V-Twin G14 1000 c.c. S.V. Vee Twin HG14-101 HG14-101 V-Twin
1938
Model Type Engine number Frame number Remarks B20 250 c.c. S.V. Tourer JB20-101 JB20-101 C10 250 c.c. S.V. JC10-101 JC10-101 B21 250 c.c. O.H.V. Sports JB21-101 JB20-101 B22 250 c.c. O.H.V. Empire Star JB22-101 JB20-101 B23 350 c.c. S.V. Tourer JB23-101 JB20-101 B24 350 c.c. O.H.V. Empire Star JB24-101 JB24-101 B25 350 c.c. O.H.V. Competition JB25-101 JB24-101 B26 350 c.c. O.H.V. Sports JB26-101 JB24-101 M19 350 c.c. O.H.V. de Luxe JM19-101 JM19-101 M20 500 c.c. S.V. Tourer JM20-101 JM19-101 M21 600 c.c. S.V. Tourer JM21-101 JM19-101 M22 500 c.c. O.H.V. Sports JM22-101 JM19-101 M23 500 c.c. O.H.V. Empire Star JM23-101 JM19-101 M24 500 c.c. O.H.V. Gold Star JM24-101 JM24-101 first Gold Star Y13 750 c.c. O.H.V. Vee Twin JY13-101 JY13-101 V-Twin G14 1000 c.c. S.V. Vee Twin JG14-101 JG14-101 V-Twin
1939
Model Type Engine number Frame number Remarks C10 250 c.c. S.V. Standard KJC10- KJC10- 1938 production C10 250 c.c. S.V. De Luxe KC10-101 KC10-101 C11 250 c.c. O.H.V. KC11-101 KC10-101 B21 250 c.c. O.H.V. Standard KJB21- KJB20- 1938 production B21 250 c.c. O.H.V. De Luxe KB21-101 KB21-101 B23 350 c.c. S.V. Standard KJB23- KJB20- 1938 production B23 350 c.c. S.V. De Luxe KB23-101 KB21-101 B24 350 c.c. O.H.V. Silver Star KB24-101 KB24-101 B25 350 c.c. O.H.V. Competition KB25-101 KB24-101 B26 350 c.c. O.H.V. KB26-101 KB24-101 M20 500 c.c. S.V. Standard KMS20-101 KM20-101 M20 500 c.c. S.V. De Luxe KM20-101 KM20-101 M21 600 c.c. S.V. KM21-101 KM20-101 M22 500 c.c. O.H.V. Standard KJM22- KJM19- 1938 production M22 500 c.c O.H.V. De Luxe KM22-101 KM20-101 M23 500 c.c. O.H.V. Silver Star KM23-101 KM23-101 M24 500 c.c. O.H.V. Gold Star KM24-101 KM24-101 G14 1000 c.c. S.V. Vee Twin KG14-101 KG14-101 V-Twin
1940
Model Type Engine number Frame number Remarks C10 250 c.c. S.V. WC10-101 WC10-101 C11 250 c.c. O.H.V. WC11-101 WC10-101 C12 350 c.c. S.V. WC12-101 WC10-101 B29 350 c.c. O.H.V. Silver Sports WB29-101 WB29-101 M20 500 c.c. S.V. WM20-101 WM20-101 M21 600 c.c. S.V. WM21-101 WM20-101 M23 500 c.c. O.H.V. Silver Star WM23-101 WM20-101 G14 1000 c.c. S.V. Vee Twin WG14-101 WG14-101 V-Twin