BSA carburettor jet settings

Original Carburettor fitment

PART No

DESCRIPTION

MODEL

YEARS

276EU/1DB

 Type 6, 15/16″ bore, vertical float chamber A7

1951-54

276C/1B

 Type 6, 1″ bore, vertical float chamber A7ST

1951-53

276BR/1B

 Type 6, 1 1/16″ bore, vertical float chamber A10

1950-53

276GG/1DB

 Type 6, 1 1/16″ bore, vertical float chamber A10

1954

276FH/1AT

 Type 6, 1″ bore, vertical float chamber B31/32

1946-54

276C/1B

 Type 6, 1″ bore, vertical float chamber M20

1939-54

276BR/1B

 Type 6, 1 1/16″ bore, vertical float chamber M21

1939-54

376/15

 Monobloc carburettor 15/16″ bore A7

1955-62

376/16

 Monobloc carburettor 1″ bore A7SS, B31, M20

1955-62

376/17

 Monobloc carburettor 1 1/16″ bore A10 S’arm

1955-59

376/17

 Monobloc carburettor 1 1/16″ bore B32

1955-57

376/17

 Monobloc carburettor 1 1/16″ bore B33, M21, M33

1955-60

389/18

 Monobloc carburettor 1 1/8″ bore A10

1960-62

389/18

 Monobloc carburettor 1 1/8″ bore B34

1955-58

389/185

 Monobloc carburettor 1 3/32″ bore

389/19

 Monobloc carburettor 1 3/16″ bore

The chart below shows the settings for most BSAs from 1937 to 1963, it is only a guide as various sources differ in the settings quoted, we have tended to use those quoted by Amal. A standard needle jet is used on the type 6 models unless a size is given. The standard needle jet on the Monobloc is .106 and needle jets are not usually marked with the size. The needle position is the number of grooves counting from the top.

Model

Years

Carb. Type

Bore

Main Jet

Slide Cutaway

Needle Position

Needle Jet

Pilot Jet
A7

1946-53

276

15/16

140

3

3

107

A7

1954

276

15/16

140

4

4

107

A7

1955-62

376

15/16

210

3.5

2

106

 25
A7ST twin carb.

1949-50

275

7/8

110

4

3

107

A7ST

1951-53

276

1

160

4

3

107

A7ST/SS

1954

276

1

170

4

3

107

A7SS

1955-62

376

1

270

3.5

3

106

30
A10

1950-53

276

1 1/16

170

4

2

.108

A10

1954

276

1 1/16

170

4

2

107

A10 Plun

1955-57

276

1 1/16

170

4

2

107

A10 S’arm

1955-59

376

1 1/16

240

3.5

3

106

 25
A10

1960-62

389

1 1/8

250

3.5

3

106

30
A10 Super Flash

1953-54

10TT9

1 1/16

360

6

4

.109

A10 Road Rocket

1954-57

10TT9

1 1/16

340

6

4

.109

B20

1937-38

74

25/32

80

5

3

B21

1937-38

74

25/32

80

4

2

B21

1939

75

7/8

120

4

3

B22

1937-38

75

7/8

120

4

3

B23

1937

74

25/32

80

5

1

B23

1938

75

7/8

110

4

3

B23

1939

75

7/8

130

4

3

B24/5/6

1937-39

76

1

160

4

3

B31/32

1946-54

276

1

150

4

3

std

B31

1955-60

376

1

260

3.5

2

106

 30
B32

1955-57

376

1 1/16

260

4

3

106

25
B33/34

1949-54

289

1 1/8

200

4

3

std

B33

1955-60

376

1 1/16

260

3.5

3

106

25
B34

1955-58

389

1 1/8

240

3

2

106

25

C10

1938-39

74

25/32

80

5

3

C10/L

1946-54

274

25/32

90

4

2

105

C10L

1955-57

375

25/32

120

3.5

2

105

25
C11

1939

74

25/32

80

4

3

C11/G

1946-54

274

25/32

80

4

3

std

C11G

1955

375

25/32

140

3.5

3

105

25
C12

1940

276

1

150

4

2

std

C12

1956-58

375

25/32

140

3.5

3

105

25

M19

1937-38

76

1

150

4

2

M20

1937-39

76

170

4

3

M20

1940-54

276

1

170

4

2

std

M20

1955-59

376

1

240

5

3

106

30
M21

1937-39

76

1 1/16

170

4

2

M21

1946-54

276

1 1/16

160

4

2

std

M21 (inc 1961 AA)

1955-61

376

1 1/16

250

5

2

106

30
M21 AA

1946-60

276

1 1/16

160

4

2

std

M22

1937-39

76

1 1/16

150

4

3

M23

1937-38

89

1 1/8

200

4

2

M23

1939

89

1 1/8

200

3

3

M24

1938-39

10TT36

1 5/32

370

5

4

M33

1949-54

289

1 1/8

200

4

3

std

M33

1955-60

376

1 1/16

260

3.5

3

106

25

Y13

1938

76

140

3

3

G14

1938

76

160

3

1

Model Years Carb. Type Bore Main Jet Slide Cutaway Needle Position Needle Jet Pilot Jet

Where the model is listed as ‘6’ this means that the part is suitable for all type 6 carburettors.