LOT 76

1953/1950 BSA 499cc B31/B33 Registration no. 127 UYF Frame no. BB31 S 3457 Engine no. ZB33.5458.

Sold for £1,725 inc. premiumLot to be sold without reserve

Previous Lot

Next Lot

Lot 76

1953/1950 BSA 499cc B31/B33

Motorcycles Online - The Summer Sale|15 June 2026, 13:15 BST|Online, Milton Keynes

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.
Key not required

Footnotes

BUYER'S PREMIUM
The Buyer's Premium for this Lot is 15%+VAT on the first £500k of the Hammer Price, and 12%+VAT on the balance thereafter.

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.

CONDITIONS OF SALE, AUCTION INFORMATION & GUIDE FOR BUYERS
Please see the 'CONDITIONS OF SALE, AUCTION INFORMATION & GUIDE FOR BUYERS' at the top of the main sale page (Motorcycles Online - The Summer Sale) for all pertinent information regarding bidder's obligations, viewing, bidding, payment, post-sale collection & transportation.

REQUEST A TRANSPORT QUOTE
To request a UK or European Motorcycle shipping quote visit Moving Motorcycles.
To request an International Motorcycle shipping quote visit Shippio.
To request a Memorabilia and Spares shipping quote visit Mail Boxes Etc - Milton Keynes.

Additional information

This auction is now finished. If you are interested in consigning in future auctions, please contact the specialist department. If you have queries about lots purchased in this auction, please contact client services.
Buyers' Obligations
ALL BIDDERS MUST AGREE THAT THEY HAVE READ AND UNDERSTOOD BONHAMS' CONDITIONS OF SALE AND AGREE TO BE BOUND BY THEM, AND AGREE TO PAY THE BUYER'S PREMIUM AND ANY OTHER CHARGES MENTIONED IN THE NOTICE TO BIDDERS. THIS AFFECTS THE BIDDERS LEGAL RIGHTS.
If you have any questions about the Conditions of Sale, please contact your nearest client services team.
From 28 June 2025, the import into the EU of non-EU property of a certain age (and in some categories above a certain value) is subject to additional requirements. Under the relevant EU Regulation, it is the Buyer's sole responsibility to assess whether any Lot meets the criteria for import into the EU. The refusal of any required Import License or Importer Statement, or any delay in obtaining such License or Statement shall not give rise to the rescission or cancelation of any Sale, nor allow any delay in making full payment for the Lot.
Buyers' Premium and Charges
Like the vast majority of auctioneers Bonhams charge a Buyer's Premium on the Hammer Price of each Lot purchased and this is subject to VAT. Some lots may also be subject to VAT on the Hammer Price and these lots will be clearly marked with a symbol (†, Ω, *) printed beside the lot number.
For Automobilia the Buyer's Premium is 28% on the first £40,000 of the hammer price; 27% of the hammer price of amounts in excess of £40,001 up to and including £800,000; 21% of the hammer price of amounts in excess of £800,001 up to and including £4,500,000 and 14.5% of the hammer price of any amounts in excess of £4,500,001.
For Motor Cars and Vehicle Registration Numbers the Buyer's Premium will be 15% on the first £500,000 of the hammer price of each Lot, and 12% on the balance thereafter.
A 3rd party bidding platform fee of 4% + VAT of the Hammer Price for Buyers using the following bidding platforms will be added to the invoices of successful Buyers for auctions starting on or after 6th July 2024 – Invaluable; Live Auctioneers; The Saleroom; Lot-tissimo.
VAT at the standard rate is payable on the Buyers Premium by all Buyers, unless otherwise stated.
Payment Notices
For payment information please refer to the sale catalog.
Shipping Notices
For information and estimates on domestic and international shipping as well as export licences please contact Bonhams Shipping Department.
- Motorcycles