Description
This motorcycle is Lot 76 of Bonhams Motorcycles Online – The Summer Sale; open for bidding 5-15th June 2026. This Lot is available for public view and eventual collection from Bonhams Motorcycle Department, Milton Keynes.
Please see the Bonhams website for full details.
Auction Timings:
Bidding on all Lots commences Friday 5 June, 12:00 noon.
Bidding closes Monday 15 June, 12:00 noon, starting with Lot 1
Each subsequent Lot will then close one minute apart unless bidding remains active.
Public Viewing (BY APPOINTMENT ONLY):
All Lots:
Wednesday 10 June, 9am - 5pm
Thursday 11 June, 9am - 5pm
Please email using the button below with your availability to schedule an appointment.
Lot 76
1953/ 1950 BSA 499cc B31/ B33
Registration no. 127 UYF
Frame no. BB31 S 3457
Engine no. ZB33. 5458.
Based on the pre-war B29, BSA's rugged and reliable B31 '350' was manufactured from 1945 to 1959, its overhead-valve engine providing the basis for the renowned Gold Star. Produced initially with rigid frame and telescopic front fork, it gained (optional) plunger rear suspension in 1949 and a swinging-arm frame in '54. A '500' version – the B33 - was manufactured from 1947 to 1960. The engine closely followed B31 lines, but with larger (85mm) bore and heavier flywheels, while the cycle parts were identical apart from a larger-section rear tyre.
Acquired by the private vendor in 2018, this BSA consists of a 1953 B31 plunger frame and a 1950 B33 engine. Refurbishments undertaken in 2024 include respraying and relining the fuel tank; overhauling the engine top end (new valves, valve guides, piston rings and small-end bush); rebuilding the clutch (new plates, pushrod, bearing); a general service (oils, spark plug, cables, gaskets filters, carburettor jet); and a magneto overhaul by Dave Lindsley (see 2019 invoice on file). It should be noted that the machine is fitted with an anti-wet-sumping tap.
Apart from a non-functioning dynamo, the machine was last started/ run in May 2026 and a video of it running may be viewed on the Bonhams website. Prospective purchasers must satisfy themselves with regard to this motorcycle's history, authenticity, originality, mechanical condition, and completeness (or otherwise) prior to bidding. Sold strictly as seen, the machine is offered with a current V5C Registration Certificate and a substantial quantity of invoices (perusal recommended). It should be noted that the HPI database records the previous colour as black and the current colour as red.
£2, 500 - 3, 500
All lots are sold ‘as is/ where is’ and Bidders must satisfy themselves as to the provenance, condition, age, completeness and originality prior to bidding. Visit the Bonhams Motorcycles website for all pertinent auction information.
