The Bonneville Shop supplies new replacement parts for classic BSA motorcycles. Most of our range covers the 1962–1972 A50 and A65 unit twins, including the Lightning, Thunderbolt, Spitfire, Hornet and Firebird, plus selected parts for the A7 and A10, A70, A75 Rocket 3 and B25, B44 and B50 singles. Shop by system below: engine, electrical, carburetor and fuel, brakes, gaskets and more. Orders ship free to the lower 48 states, and weekday orders placed by noon Mountain Time ship the same day.
Table of Contents
Shop BSA Motorcycle Parts by Category
Find the right part faster by starting with the system you’re working on.
Engine and drivetrain
- BSA Engine Parts: pistons, rings, valves, guides, cam bushes, oil pumps and timing-side parts
- BSA Gaskets and Seals: complete gasket sets, rocker-box and timing-cover gaskets and oil seal kits
- BSA Clutch and Primary: clutch plates, springs, primary chains and chaincase parts
- BSA Transmission and Gearbox: gears, shafts, bearings and gearchange parts
- BSA Chains and Sprockets: final-drive chains and gearbox and rear sprockets
- BSA Oil and Air: oil filters, air filters and oil lines
- BSA Exhausts: header pipes, silencers and fittings
Fuel and electrical
- BSA Carburetor and Fuel: Amal Concentric parts, manifolds, petrol taps and fuel lines
- Complete Carburetors: ready-to-fit carburetors
- BSA Electrical: wiring harnesses, electronic ignition, charging, switches and lighting
- BSA Instruments: speedometers, tachometers, drives and cables
Chassis and running gear
- BSA Suspension and Forks: fork parts, seals, gaiters and rear shocks
- BSA Brakes: brake shoes, linings, springs, cams and cables
- BSA Frame, Body and Trim: frame fittings, side panels, stands and trim
- BSA Wheels and Tires, Wheel Rims, Spoke Sets and Tires
- BSA Handlebars and Controls: bars, levers, grips, mirrors and switch gear
- BSA Cables: throttle, clutch, brake and instrument cables
Bodywork and finishing
- BSA Tanks and Badges: fuel tanks, badges and fittings
- BSA Fenders and Mudguards: front and rear mudguards and stays
- BSA Seats: seats, covers and fittings
- BSA Decals: tank, panel and side-cover decals
- BSA Rubber Spares: footrest rubbers, knee grips, grommets and mounts
- BSA Hardware: bolts, studs, nuts and screw sets in BSF and UNC thread forms
Tools and documentation
- BSA Service Tools: pullers, holding tools and timing tools
- BSA Parts Books: factory part numbers and exploded diagrams
- BSA Manuals: workshop and rider’s manuals
- See also our workshop tools, suspension tools, wheel and brake tools, shop supplies and clearance
Shop by BSA Model and Year
BSA parts changed with engine family, model and year, so knowing your bike’s version narrows your search quickly.
| Model family | Years | Models | Key facts |
| A7 and A10 pre-unit twins | A7 from 1946 and A10 from 1950, into the early 1960s | A7, A7 Shooting Star; A10 Golden Flash, Road Rocket, Super Rocket, Rocket Gold Star | Separate engine and gearbox; the twins that led to the A50 and A65 (Wikipedia; The Bonneville Shop) |
| A50 and A65 unit twins | 1962–1972 | A50 Royal Star, Cyclone, Wasp; A65 Star, Rocket, Lightning, Thunderbolt, Spitfire, Hornet, Firebird Scrambler | Engine and gearbox in one casting; 74mm stroke shared by both engines (Hagerty; The Bonneville Shop) |
| Oil-in-frame (OIF) twins | 1971–1972 | A65 Lightning, Thunderbolt, Firebird | Frame carries the engine oil; new forks, conical hubs and taller seat (Hagerty) |
| A70 Lightning 750 | Early 1970s (limited run) | A70L | Stroked A65; about 202 built for racing homologation (The Bonneville Shop) |
| A75 Rocket 3 | 1969–1972 model years | A75R, A75V | 750cc triple developed with the Triumph Trident; inclined cylinders and BSA frame (Wikipedia) |
| B-range unit singles | 1960s–1972 | B25 Starfire, B40, B44 Victor and Shooting Star, B50 | Jeff Smith won the 1964 and 1965 500cc Motocross World Championships on a B40 (Wikipedia) |
| Gold Star | 1938–1963 | M24, ZB, BB, CB, DB, DBD34 | 350 and 500cc singles named after Wal Handley’s 1937 Brooklands Gold Star (BSA Gold Star Owners Club) |
Most of our stock is for the A50 and A65 twins. For the other families, check each listing’s model and year fitment, or contact us before ordering.
A50 and A65 parts books by year (all in our BSA parts books category):
| Model year | Parts book |
| 1963–1965 | 00-5116 |
| 1966 | 00-5126 |
| 1967 | 00-5129 |
| 1968 | 00-5137 |
| 1969 | 00-5145 |
| 1970 | 00-5707 |
| 1971–1972 | 00-5733 |
Riding a Triumph or Norton too? See our vintage Triumph parts and Norton Commando parts hubs. Rocket 3 owners can also browse our Triumph engine and Triumph gasket categories, since many triple parts are shared with the Trident T150.
Shop by Brand
We stock British-made, original-specification and quality reproduction BSA parts from established suppliers, including:
- Carburetors and fuel: Amal
- Electrical and ignition: Lucas, Boyer Bransden, Tri-Spark, Podtronics, Sparx, Electrex World, British Wiring, Champion
- Engine: G&S Valves, Kibblewhite, Hepolite
- Brakes and suspension: Girling, Hagon, Ferodo
- Cables and controls: Venhill, Doherty, Barnett
- Chains: Renold, D.I.D
- Wheels and tires: Central Wheel Components, Excel, Dunlop
- General spares: Wassell, Emgo
Browse all brands.
A Short History of BSA Motorcycles
The Birmingham Small Arms Company was founded in 1861 to make firearms, and by 1863 its factory at Small Heath, Birmingham, was complete. BSA set up a motorcycle division in 1903, and its first motorcycle followed in 1910 (BSA Company). That first 3½ H.P. model was shown at the Olympia Show in London in November 1910, and the first season’s production sold out (Wikipedia).
In June 1937, Wal Handley won a race at Brooklands on a specially prepared BSA Empire Star, with a fastest lap of 107.57 mph. That earned him a Brooklands Gold Star badge, and BSA named its new M24 sports single the Gold Star for 1938 (BSA Gold Star Owners Club; Wikipedia). A replica of Handley’s bike is on display at Brooklands Museum. During the Second World War, BSA built 126,334 M20 motorcycles for the armed forces (BSA Company; Wikipedia).
After the war, BSA launched the 500cc A7 twin in 1946, the 650cc A10 in 1950 and bought Triumph in 1951 (The Bonneville Shop). The two-stroke Bantam, based on the German DKW RT 125, was built from 1948 to 1971 (Wikipedia; BSA Bantam Preservation Group). By the 1950s, BSA was the world’s largest motorcycle maker, and one in four motorcycles sold worldwide carried the BSA badge (BSA Company).
The unit-construction A50 and A65 twins arrived in 1962 and became the backbone of the range through the 1960s, especially in the US (Classic Bike Hub; Hagerty). The twin-carburetor A65 Lightning followed in 1964 (The Classic MotorCycle). In 1968, BSA announced the three-cylinder Rocket 3 for the 1969 model year (Wikipedia), and Dick Mann won the 1971 Daytona 200 on a BSA triple (The Bonneville Shop).
BSA recorded a £3 million trading loss in 1971, and 63 years of continuous motorcycle production ended in summer 1973 (BSA Company). A government-organized rescue that year led to the BSA-Triumph motorcycle business being taken over by Norton-Villiers, which became Norton Villiers Triumph (Wikipedia). In 2016, the BSA name was bought by Classic Legends, part of the Mahindra Group, which launched a new Gold Star in 2021 (BSA Company).
Further reading: the Birmingham Small Arms Company history, Grace’s Guide to BSA, the Wikipedia pages on the BSA A7, A50, A65, B44 and Gold Star, the BSA Motorcycle Owners Club of New Zealand on the first Gold Star, and Run Motor Run’s BSA history. Read more in our blog posts Thunderbolts and Lightning: BSA Motorbikes and Why Not a BSA?
How to Order the Correct BSA Part
- Find your engine and frame numbers. Frame numbers are usually on the front down tube or near the steering head, and engine numbers are usually on the primary side by the crankcase mouth. On oil-in-frame B-range singles, the frame number is on the prop stand bracket (BSA Owners Club).
- Decode the year. Before 1968, engine and frame numbers rarely match. From the 1969 model year, both carry the same number with a two-letter date code: the first letter is the month and the second is the model year (C = 1969, D = 1970, E = 1971, G = 1972). Model years ran from August to July (BSA Owners Club).
- Use the parts book for your year. Factory part numbers end the guesswork. See why the parts catalog is your most important tool, Year, Make, Model: What Are You Working on Today? and our BSA parts books.
- Check thread forms and earlier changes. Many A50 and A65 fasteners changed from BSF to UNC for 1969, and many bikes have been updated over the decades. Read The Nuts and Bolts of Hardware and Pattern Parts and Fettling to Perfection before fitting parts.
- Ask us. Contact our team with your model, year, and engine and frame numbers.
For factory records, the BSA Owners Club dating service can confirm your bike’s original numbers and despatch date. In the US, the BSA Owners Club of Southern California and the BSA Owners Club of Northern California offer rides, swap meets and technical help, and the Vintage Motor Cycle Club library holds a large archive of British motorcycle literature.
BSA Tech Library
Written by our technical support team, Dave Porter and Mike Grage:
Understanding the Choke on Amal Concentric MK1 Series Carburetors
Amal Concentric MK1 Choke Dave Porter, Customer and Technical Support at the Bonneville Shop Occasionally, the…
A Guide to British Motorcycle Basket Case Projects
A Guide to Motorcycle Basket Case Dave Porter, Technical and Customer Support at The Bonneville Shop The opportunity to acquire a…
Wheel Building – Starting For Success
Dave Porter, Technical and Customer Support at The Bonneville Shop. Motorcycle Wheel Building One of the more satisfying elements of the…
An Overview of the Smith’s BG5330 Speedometer Drive Units
An Overview of the Smith’s BG5330 Speedometer Drive Units By Dave Porter, Technical and Customer Support at The Bonneville Shop …
A Word About BSA, Norton, and Triumph Seat Supply
By Dave Porter, Technical and Customer Support at The Bonneville Shop If you have been searching for seat supply for…
Year, Make, Model – What Are You Working on Today?
Triumph and BSA Frame and Engine NumbersWhere are the Frame and Engine Numbers?Registration and Title Documents for Year Make Model …
BSA history and projects
- Thunderbolts and Lightning: BSA Motorbikes
- Why Not a BSA?
- Year, Make, Model: What Are You Working on Today?
- A Guide to British Motorcycle Basket Case Projects
- A Word About BSA, Norton and Triumph Seat Supply
Engine and primary
Carburetors and ignition
- Understanding the Choke on Amal Concentric MK1 Carburetors
- Amal Carb Fitment: An Everyman’s Guide
- A Look at the Amal Concentric Floats
- Setting Up Dual Carbs
- Timing Tri-Spark Ignition on Classic Twins
- Tri-Spark Triples Ignition Kit Installation Guide (A75 Rocket 3)
- Electronic Ignition System Diagnostics
Electrical
- Video: About Solid-State Regulators
- A Look at the Lucas 149SA and 47SA Ignition Switches
- Fitting the Lucas 36403 Ammeter
- The Lucas Cutout and Kill Switches
- Using LEDs with Traditional Turn Signal and High Beam Indicators
- An Overview of the Smiths BG5330 Speedometer Drive
Chassis, wheels and controls
- Wheel Building: Starting for Success
- Lacing a Cross 3 Pattern Rear Disc Wheel
- A Brief Guide to Cables
- Considerations for Handlebar Changes
Restoration and care
- The Case for the Parts Catalog
- Pattern Parts and Fettling to Perfection
- The Nuts and Bolts of Hardware
- Video: Polishing Primary and Timing Covers
- Application Techniques for Waterslide Decals
- Winterizing Your Classic Brit Bike Checklist
Browse all BSA tech articles or the full Tech Blog, or watch our videos on The Bonneville Shop YouTube channel.
Why Buy BSA Parts from The Bonneville Shop
- Keeping British bikes on the road since 2008. The Bonneville Shop was founded in Ventura, California, in 2008 by British ex-pat Roger Tedds (About Us).
- Experienced technical support. Dave Porter and Mike Grage have more than 60 years of combined experience with classic British motorcycles (About Us).
- Free shipping to the lower 48 states, with no minimum order. Standard orders ship by USPS, and expedited shipping is available (Shipping and Returns).
- Same-day shipping for orders received Monday to Friday before noon Mountain Time (Shipping and Returns).
- International orders. Email your parts list and address to orders@thebonnevilleshop.com for a shipping quote.
- 30-day returns on most products. Bearings, service tools, electrical items and clearance “2nd’s” are not returnable (Shipping and Returns).
- Rewards on every order through Frequent Spanner Points.
BSA Motorcycle Parts FAQ
Which BSA models do you sell parts for?
Most of our BSA parts are for the 1962–1972 A50 and A65 unit twins, including the Lightning, Thunderbolt, Spitfire, Hornet, Firebird Scrambler, Royal Star and Cyclone. We also carry selected parts for the A7 and A10 pre-unit twins, the A70, the A75 Rocket 3 and the B25, B44 and B50 singles. Check each listing for model and year fitment.
What is the difference between the BSA A65 and A10?
The A10 is a 650cc pre-unit twin, with the engine and gearbox in separate cases. The A65, introduced in 1962, is a unit-construction 650 twin, with the engine and gearbox in one casting. It was developed from the A7 and A10 design, but most engine parts do not interchange (The Bonneville Shop; Hagerty).
What is the difference between the BSA Lightning and Thunderbolt?
Both are A65 650 twins. The Thunderbolt has a single carburetor and was aimed at touring. The Lightning has twin carburetors, a tachometer and a sportier engine specification (The Bonneville Shop).
Do BSA A50 and A65 engines share parts?
Yes, many. Both engines have a 74mm stroke and the same cylinder spacing, so the bottom ends are effectively the same. The barrels, pistons, pushrods and cylinder heads differ (The Bonneville Shop). Always check the listing, because some parts changed by year.
What is a BSA oil-in-frame (OIF) model?
From 1971, BSA’s twins and B-range singles used a frame that carries the engine oil instead of a separate oil tank. The OIF models also had new forks, conical hubs and a taller seat, so many chassis parts differ from 1970 and earlier bikes (Hagerty).
Do BSA Rocket 3 parts fit the Triumph Trident?
Many do. The BSA Rocket 3 and Triumph Trident T150 were developed together and share most engine components. The Rocket 3 has forward-inclined cylinders and its own BSA frame, so frame, cylinder-related and some engine parts differ (Wikipedia).
How do I find out what year my BSA is?
Check the engine and frame numbers. From the 1969 model year, both carry the same number and a two-letter date code: the first letter is the month and the second is the model year (C = 1969, D = 1970, E = 1971, G = 1972). Model years started in August of the previous calendar year (BSA Owners Club). For earlier bikes, use the BSA Owners Club number lists or its dating certificate service.
Which BSA parts book do I need?
Use the book for your bike’s model year. For A50 and A65 twins, we carry parts books 00-5116 (1963–65), 00-5126 (1966), 00-5129 (1967), 00-5137 (1968), 00-5145 (1969), 00-5707 (1970) and 00-5733 (1971–72) in our BSA parts books category.
Do you sell electronic ignition for BSA motorcycles?
Yes. We stock Tri-Spark and Boyer Bransden electronic ignition, including systems for the A75 Rocket 3 and B-range singles, along with wiring harnesses and charging parts in our BSA electrical category.
Do you offer free shipping on BSA parts?
Yes. Orders ship free to the lower 48 US states, with no minimum order. Orders received Monday to Friday before noon Mountain Time ship the same day, and later orders ship the next business day. Expedited shipping is available for an extra charge.
Do you ship BSA parts internationally?
Yes. If an international shipping quote looks high, email your parts list and shipping address to orders@thebonnevilleshop.com, and we will check the shipping cost for you.
What is your return policy?
Most products can be returned within 30 days of delivery. Bearings, service tools, electrical items and clearance “2nd’s” products are not returnable. Full details are on our Shipping and Returns page.
Can I get help choosing the right BSA part?
Yes. Call 720-570-7884 or text 720-260-4271, Monday to Friday, 9 a.m. to 5 p.m. Mountain Time. You can also email orders@thebonnevilleshop.com. Please include your model, year, and engine and frame numbers.
Can I pick up parts in Cheyenne?
Yes. Orders can be picked up at 190 S College Dr., Unit C, Cheyenne, Wyoming 82007. This is a pickup location only, not a retail store open to the public.