The ex-Bob Brown,1955 Matchless 498cc G45 Racing Motorcycle
Lot 361
The ex-Bob Brown,1955 Matchless 498cc G45 Racing Motorcycle
£27,000 - 32,000
US$ 45,000 - 53,000
Lot Details
The ex-Bob Brown
1955 Matchless 498cc G45 Racing Motorcycle
Engine no. G45 225
One of the oldest of British motorcycle manufacturers, Matchless pursued a vigorous competition policy in its early years, founder’s son Charlie Collier winning the inaugural Isle of Man TT (single-cylinder) race of 1907 and repeating the feat in 1910, brother Harry having brought home the honours in 1909. However, by the 1930s Matchless had ceased to be thought of as a racing marque, and after WW2 the firm, by now reconstituted as Associated Motor Cycles having acquired AJS, chose the latter’s badge for its competition machines. In this context the arrival of a new Matchless racing motorcycle in 1951 caused something of a stir.

The prototype of what would become the G45 first appeared at the ’51 Manx Grand Prix with Robin Sherry in the saddle, eventually finishing fourth after a promising debut. In fact the machine was not an entirely new design but a hybrid comprised of AJS 7R-based cycle parts into which was installed a tuned Matchless G9 roadster engine. The engine’s bottom-end remained more-or-less stock G9 and retained AMC’s unique centre-bearing crankshaft, but above the crankcase there was a new aluminium-alloy cylinder barrel and ’head, the latter sporting distinctively finned exhaust rocker boxes. Fuel was supplied by a single Amal TT carburettor and exhausted via short, megaphone-ended pipes.
In 1952 the prototype G45 garnered much valuable publicity and not a little controversy when Derek Farrant - later an AJS works rider on both Porcupine and 7R3 - won the Senior Manx Grand Prix after leading from start to finish. Strictly speaking, a works prototype had no business running in an event for amateur riders riding over-the-counter machines, but AMC quickly announced that a production G45 would be available for 1953. Although still based on that of the G9, the engine of the production version incorporated a different camshaft opening the valves via roller-ended followers, and breathed via a pair of Amal GP carburettors mounted either side of a central float chamber. Claimed power output was 48bhp at 7,200rpm, increasing on later models to 54bhp at 7,400 revs.

Apart from revised valvegear and the adoption of a forged crankshaft, the G45 changed little over the course of its life, and what developments there were did not keep pace with the opposition. Production ceased in 1957 after around 80 machines had been built, of which approximately half are thought to survive worldwide today.

This superbly restored Matchless G45 is believed to be that campaigned by Australian Bob Brown in the mid-1950s; this information, we are advised, having been divulged to the vendor by no less than the late Umberto Masetti, 500cc World Champion for Gilera in 1950 and 1952. Masetti first encountered the Matchless-mounted Brown during the 1956 Grand Prix season and recommended the Australian to Gilera, which entered him on works fours in the 1957 Isle of Man TT where he finished third in both the Senior and Junior races. After Bob Brown’s fatal accident while riding a works Honda at the German Grand Prix in 1960, the Matchless remained in Europe and spent many years in a museum in Switzerland. Restored at date unknown, the machine was purchased directly from the museum by the current owner.
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