Wed, 6th Apr 2022 13:00

National Motorcycle Museum

Lot 347

1955 BSA B31 Trials Special

Sold for £4,600

(including buyers premium)

Lot details

Registration No: RSJ 839
Frame No: CB31 8048
Engine No: BB32A 305
CC: 350
MOT: Exempt

  • Part of an enthusiast private collection for over 20 years.
  • BSA Owners Club dating certificate issued in 1998
  • Frame numbered in Nov '55 but taken off the production line
  • All alloy 350 competition BB32A engine number
  • Fitted with 'TRI' stamped gearbox and 'Lucas Racing' badged magneto
  • Unused for a number of years, supplied with a current V5C

The Birmingham Small Arms factory was established in the Small Heath area of Birmingham in 1861 and as the name suggests manufactured weapons. Around the turn of the century they started making bicycles and progressed onto motorcycles a few years later. BSA went on to be one of the world's largest producers of motorcycles up until its demise in the early 1970s.

This very interesting trials bike is based around a 1955 B31 frame with an all alloy BB32A competition engine. A dating certificate from the BSA Owners Club suggest that frame number CB31 8048 was manufactured in November or December 1955 but 'no despatch records exist as it was taken off the production line for some reason'. It also states that the engine number matches 'a 350cc alloy competition engine from the same period'. Unfortunately, we cannot find any further history on the bike, only that it acquired its age related registration number in 1998. Part of an enthusiast private collection of mainly British off-road bikes it comes fitted with a Lucas racing mag and the gearbox cover is stamped 'TRI' together with its all alloy top end. Unused for a number of years it will require a good recommissioning before use but will make a good starting point for a pre '65 trials bike or classic green lane bike. It comes with its dating letter and a current V5C.

For more information, please contact:
Ian Cunningham
07415 871189


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