I followed with interest the saga of the BSA B21 reconstruction by John Lay. In June last year I bought a partly-rebuilt although not quite catalogue K24 model 1939 350. I didn’t know until later that it is a Silver Star, apparently only available for one year. I came across similar difficulties as John, as well as an engine and gearbox which I understood had been rebuilt. This work wasn’t done by my friend from whom I bought the bike, and the rebuild wasn’t done well, so unexpected work was needed in that area. Fortunately most of the tinware was present, although not the lovely valanced mudguards. The petrol tank appeared sound (of which more later), but I don’t spend mortgage money on chrome so it is painted.
A new Armour exhaust and several other new bits came in a box. When it came to building the engine and gearbox I was greatly helped by a manual from BMS. As the motor is one year different from the frame, I had similar difficulties to John with the primary chaincase. Making a rear stand brought its own problems. I used conduit, as previous experience told me that push bike parts are not strong enough.
Had I known a little more about BSA, as John clearly does, I might have saved time and effort in several directions. It would have been useful to know that C11 clutch parts are similar. Fortunately the chainwheel is sound, as is the gearbox sprocket. I had expected the gearbox to be a pain, as the layshaft is slightly bent and I was not prepared to attempt straightening it. The biggest problem is the slow change from third to second as there is insufficient backlash between the mating dogs.
The DVLA coughed up an age-related V5C. I was greatly assisted by the BSAOC who charged me a very reasonable £15 ( VMCC take note) for a dating certificate. Thank you.
There is minor cyclical noise when riding slowly, which I suspect comes from the shaft. The engine is reasonably oil tight, although not brilliant. I have built numerous bikes and rarely get them as oil tight as I would like, even after much care flattening mating faces. I used Stormguard Extra-thick draught proof for the primary case. A £10 autojumble dynamo and £2 control box are working to design spec, you can’t get much better than that – but I thought £52 for the loom was a bit steep!
The BSA goes well enough, although the relined brakes leave much to be desired, and the reconditioned motor is harsh, mostly due to the high mileage timing wheels. Still it looks good enough, starts readily and has good power. The exhaust is too noisy and there’s an annoying oil leak. I reached 300 miles with no serious problems although the next owner would be advised to repair the fork spindles. It was worth the effort and I enjoy riding it, depending on my mood. At 350 miles the petrol tank began to leak. I refuse to use liners so will repair from the outside. The kickstart quadrant is worn but I’m told M20 ones fit. So on it goes!
Thanks for the updates, Lloyd. We have a very similar situation with our BSA single – whenever Frank triumphantly rectifies the last problem, I unsportingly find the next one! Old bikes: always a work in progress?