Market Segment:
Classic British military motorcycle parts.
Value Proposition:
Essential resource for BSA M20 owners, restorers, and parts suppliers seeking accurate part identification and availability.
Key Feature 1:
Comprehensive listing of OEM-equivalent part numbers.
Key Feature 2:
Categorized breakdown by motorcycle system.
Key Feature 3:
Facilitates efficient parts sourcing for restoration and maintenance.
Engine Parts:
Engine assembly, cylinder head, cylinder block, piston, crankshaft, connecting rod, camshaft, valve train components, timing gears, lubrication system components.
Transmission Parts:
Gearbox components, gears, shafts, selector mechanism, clutch components (plate, hub, basket).
Chassis Parts:
Frame components, front fork assembly (springs, dampers, sliders), rear suspension components (shock absorbers, swingarm), handlebars, footrests, seat mounting.
Fuel System Parts:
Carburetor components (jets, floats, needles), fuel tank, fuel lines, fuel taps.
Electrical System Parts:
Magneto ignition components, dynamo, wiring loom (where specified), lighting components (headlamp, taillight), switches.
Braking System Parts:
Front brake drum and mechanism, rear brake drum and mechanism, brake levers, cables.
Exhaust System Parts:
Exhaust pipe, silencer (muffler).
Wheels And Tires:
Wheel rims, spokes, hubs, tire sizes (implied), inner tubes.
Control Mechanisms:
Throttle controls, clutch lever, brake levers, gear change mechanism.
Identification Of Parts:
Facilitates identification of correct replacement parts using unique part numbers.
Assembly Reference:
Provides reference for correct component assembly and ordering.
Troubleshooting Assistance:
Indirectly assists troubleshooting by clearly identifying all components within a system.
Technical Depth:
Detailed breakdown of all components with associated part numbers, ideal for parts ordering and restoration.
Engine Type:
4-stroke, OHV
Engine Displacement Cc:
496
Engine Bore Stroke Mm:
82 x 95
Engine Configuration:
Single Cylinder
Engine Cooling:
Air Cooled
Engine Power Hp:
~14 hp @ 4,000 rpm (approximate)
Top Speed Mph:
~65 mph (approximate)
Carburetor Type:
Amal (various models common, e.g., Monobloc)
Fuel Type:
Petrol (Gasoline), leaded (historically)
Lubrication System:
Wet Sump
Ignition System:
Lucas Magneto
Oil Change Interval:
Historically, every 1,000-1,500 miles or annually, depending on usage. Modern recommendations may vary.
Valve Clearance Check:
Recommended every 2,000-3,000 miles or annually.
Spark Plug Replacement:
Typically every 3,000-5,000 miles.
Engine Oil Type:
SAE 50 or SAE 20W-50 motorcycle-specific oil recommended. Consult specific manuals for precise grades.
Engine Oil Capacity Litres:
~2.0 Litres (4.2 Pints)
Gearbox Oil Type:
EP 80W Gear Oil or equivalent.
Gearbox Oil Capacity Litres:
~0.5 Litres (0.9 Pints)
Fork Oil Type:
Tractor hydraulic oil or SAE 10W fork oil.
Common Issue 1:
Oil leaks from engine seals and gaskets.
Common Issue 2:
Wear in the gearbox, particularly selector forks and bushes.
Common Issue 3:
Magneto ignition system maintenance and timing.
Common Issue 4:
Carburetor tuning and wear (e.g., Amal).
Common Issue 5:
Worn brake linings and cable adjustments.
Brand Origin:
Birmingham Small Arms Company (BSA), established 1861 in Birmingham, England.
Brand Reputation:
Renowned for quality firearms and motorcycles, particularly their military offerings.
M20 Development:
Developed as a robust, reliable military motorcycle, widely used by British and Commonwealth forces during WWII.
M20 Significance:
Became the standard British Army motorcycle, known for its simplicity and durability in harsh conditions.
Production Period:
1937-1950
Production Volume:
Tens of thousands produced, particularly for military contracts.
Manufacturing Location:
BSA factories in England.
Military Service:
Served as the primary motorcycle for numerous military campaigns and roles, demonstrating exceptional reliability.
Durability Rating:
High, specifically designed for rugged military environments.
Military Specification Compliance:
Manufactured to strict British military specifications for wartime service.
