Carburetter and Air Filters

Part No

Description

Model

Years

GS275

Amal type 6 carburettor 74,75,274,275 1939-54

GS276

Amal type 6 carburettor 76,276 1939-54

GS289

Amal type 6 carburettor 89,289 1939-54

GS375

Amal Monobloc carburettor 375 1954-58

GS376

Amal Monobloc carburettor 376 1954-58

GS389

Amal Monobloc carburettor 389 1954-58

622/208

Amal Concentric Mk1

622/209

Amal Concentric Mk1 1/2

For gasket sets click here; for petrol pipe, taps and fittings click here; for cables click here.

The original Amal carburettors had brass bodies and separate float chambers, and were known as types 4, 5, 6 and 29. They were fitted from 1929 until 1933 when the body material was changed to a zinc die cast alloy. These were known as types 74, 75, 76, and 89, and can be distinguished from the later types because these have four air holes around the base of the body which the next type do not. In 1939 types 274, 275, 276 and 289 were introduced; these have two internal primary air passages in the base of the jet block. A later version with an ‘R’ suffix denotes that the primary air passage hole was moved to the air intake.
1955 saw a completely new carburettor being manufactured that had the float chamber cast in one piece with the mixing chamber, which is why it is called the ‘Monobloc’, these are types 375, 376, and 389.
1965 saw another complete redesign which produced the ‘Concentric’ carburettor which as it’s’ name implies has the float bowl concentric with the mixing chamber.
Each number mentioned above indicates a different casting. Each casting was capable of being machined to any one of several sizes. The carburettor type is not sufficient information when searching for a replacement, the bore or choke size is also needed. The suffix shown after the type on the flange indicates which jets, float chamber and to which machine it was originally fitted, it is irrelevant providing the body is of the correct size and the correct jets etc are used.

Carburettor Sleeving

A major cause of poor running, particularly idling, is caused by wear between the body and the slide. Fitting a new slide in a worn body is like fitting a new chain on old sprockets, a waste of time. We can rectify this by boring the body oversize and hard chrome plating the slide (type 6) or fitting a sleeve to the slide (Monobloc). This is a long lasting solution due to the materials used and is preferable to fitting a non-original, later type of concentric carburettor. The new carburettors that are now available have improved materials but are not as good as a sleeved carburettor. For the sleeving work we need to have the body, throttle slide, jet block and mixing chamber lower nut. The prices for re-sleeving are given in the price list by RES169 or RES170 for a complete overhaul. While we are sleeving the body we can replace other worn, missing or damaged parts, check threads, re-plate the fittings, peen the body parts and re-assemble for about £175 including the sleeving, leaving you with a better than new carburettor.

Original Carburetor 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

389/18.5

Monobloc carburettor 1 5/32″ 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.

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