BSA Motorcycles 1960s

BSA C15 Specifications

BSA SERVICE SHEET No. 428

Reprinted October. 1964

USEFUL DATA

C15

CI5T

C15S

Cl5
Sport Star

Engine Number

Left-hand side of the engine below cylinder

Frame Number

At the top of the steering head tube

ENGINE:

Capacity (c.c.)

249

249

249

249

Cylinder bore (mm.)

67

67

67

67

Stroke (mm.)

70

70

70

70

Compression ratio

8 to 1

8 to 1

10 to 1

8.75 to 1

Inlet opens B.T.D.C.

26

41.5

41.5

51

Inlet closes A.B.D.C.

70

62.5

62.5

68

Exhaust opens B.B.D.C.

61.5

62.5

62.5

78

Exhaust closes A.T.D.C

34.5

41.5

41.5

37

Piston rings (compression) (in.)

0.0625 wide

0.0625 wide

0.0625 wide

0.0625 wide

Piston rings (scraper) (in.)

0.125 wide

0.125 wide

0.125 wide

0.125 wide

Piston ring gaps:

Minimum (in.)

0.009

0.009

0.009

0.009

Maximum (in.)

0.013

0.013

0.013

0.013

Sparking plug

N5 Champion

N5 Champion

N3 Champion

N4 Champion

Plug points gap:

Minimum (in.)

0.02

0.02

0.02

0.02

Maximum (in.)

0.025

0.025

0.025

0.025

After Engine C15T-1251 and C15S-2112 valve timing is:-

Inlet opens B.T.D.C.

51 deg

Inlet closes A.B.D.C.

68 deg

Exhaust opens B.B.D.C.

78 deg

Exhaust closes A.T.D.C.

37 deg

TRANSMISSION:

Gear ratios--Top

5.98

9

9

6.36

Third

7.65

14.67

10.8

7.64

Second

10.54

22

14.94

10.54

First

15.96

28.53

19

13.44

Clutch friction plates

4

4

4

4

Clutch Spring Free Length 1.66" 1.66" 1.66" 1.66"

Chain sizes-Front (in.)

3/8 Duplex

3/8 Duplex

3/8 Duplex

3/8 Duplex

(70 pitches)

(70 pitches)

(70 pitches)

(70 pitches)

Rear (in.)

1/2 x .335

1/2 x .335

1/2 x .335

1/2 x .335

(112 pitches)

(122 pitches)

(122 pitches)

(112 pitches)

Teeth on--Engine sprocket

23T

23T

23T

23T

Gearbox sprocket.

17T

15T

15T

16T

Clutch sprocket

52T

52T

52T

52T

Rear chain wheel

45T

60T

60T

45T

Alternatives:- Gearbox Sprockets 17, 18, 19 & 20 Rear chain wheel 52, 56 & 60

CAPACITIES:

Fuel tank (galls.)

3

2

2

3

(13.6 Ltr)

(9 Ltr)

(9 Ltr)

(13.6 Ltr)

Oil tank (pints)

4

5

5

4

(2 1/4 Ltr)

(2.8 Ltr)

(2.8 Ltr)

(21/4 Ltr)

Gearbox (pints)

2/5 (220cc.)

2/5 (220cc.)

2/5 (220cc.)

7/16 (250cc.)

Front forks (pints)

1/6 (100cc.)

1/3 (190cc.)

1/3 (190cc.)

1/6 (100cc.)

Primary chain case (pints)

1/4 (140cc.)

1/4 (140cc.)

1/4 (140cc.)

1/4 (140cc.)

After engine C15-26792 & B40-2402 the gearbox capacity was increased to 1/2 pint (285cc)

WHEELS:

C15

C15T

C15S

C15
Sport Star

Rim size Front

WM2-17

WM1-20

WM1-20

WM2-17

Rim size Rear

WM2-17

WM3-18

WM3-18

WM2-17

Tyre size Front

3.25-17

3.00-20

3.00-20

3.25-17

Tyre size Rear

3.25-17

4.00-18

4.00-18

3.25-17

Brakes, dia. x width:

Front (in.)

6x7/8

7 x 1 1/8

7 x 1 1/8

6x7/8

Rear (in.)

6x7/8

6x7/8

6x7/8

6x7/8

Rim Offset (Front & Rear) 5/32 5/32
Hub Outside Diameter 7 7
Hub Spoke Width 2 1/4 2 1/4
Spoke Length (below the head) 5 7/16 5 7/16
Spoke Dia 10Gauge (1/8) 10Gauge (1/8)

CARBURATION (AMAL):

Bore (in.)

7/8

7/8

1.0625

1

Main jet

140

140

190

200

Pilot jet

25

25

25

25

Throttle valve

375/4

375/4

376/3.5

376/4

Needle position

3

3

2

2

Needle jet

0.1055

0.1055

0.106

0.106

GENERAL DETAILS:

Front suspension movement (in.)

5

5

5

5

Rear suspension movement (in.)

2.375

2.375

2.375

2.375

Generator output

60 watts

60 watts

60 watts

60 watts

Contact breaker gap (in.)

0.015

0.015

0.015

0.015

Battery capacity

13 amp/hr at 20 hr rate

13 amp/hr at 20 hr rate

Overall length

78

81

81.5

78

Wheelbase (in.)

51.25

51.75

51.75

51.25

Ground clearance (in.)

5

7.25

7

5

Saddle height (in.)

30

33

32

30

Overall height (in.)

37

42

41.5

36

Handlebar width (in.)

26

31.125

31.125

27

Steering head angle

65 deg

63 deg

63 deg

65 deg

Steering lock angle

50 deg

60 deg

60 deg

50 deg

Weight (lbs.)

275

265

265

275

Tyre pressures Front (lbs.)

16

19

19

17

Tyre pressures Rear (lbs.)

22

16

16

21

The recommended inflation pressures are based on a riders weight of 140 lb. Increase the tyre pressures as follows, If the rider's weight exceeds 140 lb.

Front tyre: Add one lb. per square inch for every 28 lb. increase above 140 lb.

Rear tyre: Add one lb. per square inch for every 14 lb. increase above 140 lb.

If a pillion passenger or luggage is carried, the actual load bearing upon each tyre should be determined and the pressures increased in accordance with the Dunlop Load and Pressure Schedule.


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