BSA M20 - Useful Data

USEFUL DATA
Engine bore
82 mm
Engine stroke M20
94 mm
Engine stroke M21
112 mm
Engine Capacity
496cc
Petrol tank capacity
3 gallons
Oil tank capacity
5 pints
Gearbox capacity
1 pint
Inlet tappet clearance (cold)
.010”
Exhaust tappet (cold)
.012”
Compression M20
4,9:1
Compression M21
5:1
Tyres
3.25/3.50-19
Tyre Pressure
22psi
Piston ring gap
.008 - .012”
Piston clearance Bottom of skirt
.0035 - .0055”
Piston Ring side clearance
.002" - .004"
Ignition timing
7/16” BTDC
Magneto point gap
.012”
Spark plug gap
.012 - .018”
Carburetter- Jet
170
Carburetter- Needle
2nd notch
Engine Sprocket
19 teeth
Clutch sprocket
43 teeth
Gearbox Sprocket
18 teeth
Rear Wheel Sprocket
42 teeth
Primary Chain
95 links
Gear Ratio- Top
5.3
Gear Ratio- 3rd
7.0
Gear Ratio- 2nd
10.9
Gear Ratio- 1st
15.8