BSA M33 Parts & Spares
The M33 is the overhead-valve member of BSA’s heavyweight M range: the bottom end and chassis that carried the side-valve M20 and M21, with a pushrod top end above it. It was bought as a sidecar machine as often as a solo, and the ones still in use are usually pulling something.
That layout decides how you order for it. Below the barrel an M33 is M-series, and above it the parts belong with BSA’s overhead-valve singles, which is why our listings for this model regularly name two or three machines at once.
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€ 54,00 Select options This product has multiple variants. The options may be chosen on the product page -
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Two parts books, one motorcycle
Treat the engine as two halves. Crankcases, timing side, gearbox, clutch and the whole cycle side follow the M20 and M21, so anything listed for those models is worth checking first. The head, barrel, valve gear and pushrods come from the overhead-valve 500 single instead, which is why M33 items so often appear on a listing beside the B33. Where a component carries both references we say so. Where only one model is named, take the listing at its word and send us a question rather than an assumption.
What we stock
- Top end — inlet and exhaust valves with guides, head gaskets, piston rings
- Bottom end — big end assemblies, bushes and timing side components
- Clutch — friction plate sets and springs
- Transmission — engine and gearbox sprockets, chains, kickstart parts
- Cycle parts — brake, control and fastener items shared across the M range
Solo or outfit?
Gearing is the first thing a chair changes, and a set of sprockets is cheaper to get right than to send back. Tell us what the machine is pulling and include the engine number.