Restoration guide - BSA B32/34

[01] Engine

Aluminium crankcases housed a single timing side roller main bearing with a ball and roller on the drive side. These supported a built up crank assembly with a roller big-end, the 88mm stroke was common to both engines. Barrels were iron, or alloy, with separate pushrod housings. Theseeventuallychanged to one-piece aluminium castings while a shorter con rod reduced the height of the engine. A 71mm piston for the B32 gave 348cc, that for the

B34 was 85mm for 499cc.

Inside the timing case and behind an out-rigger plate, separate camshafts operated the tappets and an intermediate gear to the magneto. There was also a

gear type oil pump. Engines with separate pushrod tunnels had access

to the tappet adjusters for the rockers operating the valves, one inlet, one exhaust. The 1952-onBB Gold Star-type cylinder

head used eccentric rockerspindlesforvalve adjustment. A I ½uin Amal 276 carburettor supplied mixture for the 350, a I ¼in 289 performed the task for the 500. For 1955, these were upgraded to the corresponding Monobloc- type. Spares availability is generally excellent, with only the alloy castings

difficult to find.

[02] Transmission

The earlier models had a pressed steel primary chaincase. Inside, there was a face-cam crankshaft shock absorber and a single-row chain to a five-plate clutch. This transferred drive to a four-speed gearbox, tried and tested in the long-established M20. The swinging arm frames had alloy primary chaincases

and a new shell for the gearbox, but the internals remained much as before. Factory supplied alternative

ratios saw the cases stamped accordingly, e.g. TR = trials, SC = scrambles. The rear wheel combined sprocket and brake drum had options of 43 or 46 teeth. Mechanical competence rather than any need for arcane knowledge should see restoration achieved. After six or seven decades, the clutch is entitled to become tired, so worth

checking for smooth operation. The gearboxes were also tough, the change mechanism is possibly the most vulnerable area. Again,

in view of component age, well worth giving everything a thorough inspection. From routine service items even to some of the more obscure gearbox components everything

should be obtainable.

[03] Electrics

The systems were wholly supplied by Lucas. The

choice was either a magdyno, complete with

the necessary ancillaries to supply a six-volt battery for the lights and horn;

alternatively, bikes could also be supplied with a magneto only, in which case a bulb horn was fitted. As usual, an

aftermarket part can always be substituted for a Lucas item missing, or

beyond restoration.

[04] Cycle parts

Original frames were singletube, with a lower twin-tube cradle completing the loop. Toe bolt-on sub-frame was rigid, an optional plunger version was offered from 1949. In 1954, a new twin downtube frame appeared, rigid or plunger, and the new BSA swinging arm frame an additional choice. This had first appeared on the previous year's Gold Stars, but from 1955 became standard for both

B32 and B34s.

Front and rear hubs had ball-journal bearings and single-sided seven-inch brake drums. Front hub was laced into a WMI-21 rim with a 2. 75 trials tyre,

rear rim was WM3-19, with 4.00 section rubber. Mudguards were blade type, and chrome plated. Tinware was a steel fuel tank, reduced in size over the years until supplanted

by a two-gallon alloy item on the swinging arm bikes. Toe oil tank was B31, modified for early bikes with high-level exhausts. This gave way to a central steel tank, a feature of all ensuing versions. Saddle was a typical Terry solo trials perch, but a dual seat became an optional extra.

[05]

Suspension

Trials competitors took a while to be convinced of the benefits of rear suspension,

but the plunger frame gradually gained popularity with its undamped springs and limited movement. Toe later swinging arm frame was common to most of BSA'sbigger models with Metalastik bushes at the pivot. Front suspension on all models was by BSA's single-damped

telescopic forks.

With the B32/B34 cycle parts also common to other models restoration should be easy as the aftermarket has usually responded quickly to the dwindling

NOS sources.