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THE “GOLD STAR” Roy Hems
Ex Manager of Godfreys Ltd, BSA East London Main Dealer Specialists Part 2 (continued from June TUG) One of the oddities of Gold Star`s was that the 350 was only a fraction slower than the 500, in all the development stages, all the technologies were applied to the ZB32 and were only, when it appeared 18 months later, applied to the ZB34. The B34 was not the test bed. However, the ZB series did have a problem, maximum revs were 6,600, but when fitted with either the Scambles set of cams or the Road Racing set, should a gear be missed or the engine over revved, there was the very distinct possiblity that the heads of the valves would touch, causing the head of one to break off causing serious damage. The correction for this was made with the introduction of the BB series late 1952. As I mentioned before, Valve Guides and Spring Seats were constantly being changed to eradicate this problem At this time, with the BB series, there was a very distinct change in the engines from the standard B31 and B33., apart from the fact the G.S.`s were alloy top half and the standard B range were cast Iron. The Rocker boxes were separated from the Cylinder heads, The valve angles were changed from 37 to 33 degrees for both, Valves diameters were increased and the ports opened up. This change allowed the revs to increase to around the 7,000 mark with reasonable safety. The BB also saw the change from Plunger suspension to swinging arm and a duplex frame, long overdue. By the time the CB series was introduced in 1953 there were some more radical changes again. Massive engine finning, shorter Con Rod, with an oval Flywheel to accomodate the lower piston setting at BDC, creating a slower piston speed. Valve adjustment was obtained by an eccentric Rocker Spindle to reduce the reciprocating weight of the rockers. Crankpin material was changed to EN36 and Nimonic 80 Exhaust Valves were fitted. This increased the power considerably. Clip-on Bars were fitted as standard. For 1955 DBD`s, due to the regulations set down by the ACU for Clubman`s TT machines Lighting had to be a standard fitment, so the Racing BTH and Lucas Magneto was replaced by a standard Lucas Magdyno, as the standard “B & M” Range were already equipped. The `A` type Gearbox, which was operated by Cam plate instead of the shaft, with cosmetic changes. Practically all the necessary combinations of Compression Ratios, later variations had a compressed foil cylinder head gasket instead of the copper and asbestos of the ZB series. This facilitated a much closer seal by the adjustment of the fit through the removal of foil layers, This adjustment was very complicated to do properly requiring a high degree of skill, quite a rare commodity at that time. Cam combinations, Exhaust lengths, Ignition Timing etc etc, had been arrived at, Most other items were still the ancilliary parts from the ZB`s. For models other than the
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