BSA  D.3 Bantam , 1955

This machine has been extensively reworked by us, with a 12 volt fully rectified electrical system being installed . The lighting system is much improved over the original.

The engine has been substantially modified for extra performance in todays urban traffic situation,and is in a scrambles state of tune.

 The crankcase volume has been reduced by the fitment of internal aluminium sheet discs,and a much stronger connecting rod fitted,together with a caged needle-roller big-end .

The transfer ports have been blended in with the crankcase mouth transfer apertures, and a 0.875" carburettor fitted to a down-draughted inlet stub,bronze-welded to the reworked barrel.

The cylinder head was entirely welded up, and a new combustion chamber machined in , centrally located within a wide squish -band. The compression ratio is 11:1, measured from the bottom of the stroke rather than from  exhaust-port closure , and  a central sparking plug replaces the original inclined item.

The exhaust system has been converted to an absorption-type silencer that is installed within the pattern short torpedo, and has an additional variable baffle arrangement.

This was essential, as the silencer as supplied was so restrictive as to barely allow the engine to run at all. The exhaust note is a joy to listen to.

 By reason of the larger carburettor, the toolbox had to be moved from its original position behind the air-filter,and now sits to the right of the machine on specially fabricated brackets, where it serves as a battery box and a housing for the rectifier.

The front brake drum was skimmed,and relined with oversized modern brake-linings that were subsequently turned to size.

The machine is an amiable little thing to ride, with spirited acceleration in traffic.It should also do well on light-to moderate off - tarmac riding as it is both extremely light and robust,as well as having useful power. 

Great fun!

"The experience was rather like taking off in a Sopwith Camel from a grass airfield. Exhilarating but slightly scary...... No matter, as you say, 'a hoot', it was starting first kick without any carb tickling or use of carb strangler" - Quote from owner

Site created by Websitedesigner