Ask any classic motorcycle enthusiast which marque first brought a 500cc World Championship trophy back to Britain and it is odds-on that most would answer with Norton. That would be a logical and unsurprising result given the many wins scored by that company’s relatively simple but hugely effective single-cylinder racers throughout the 1930s and the legendary Geoff Duke’s three World Championships for the team in the early 1950s.
In fact, the first winner of the first FIM World 500cc Championship in 1949 was Les Graham on an AJS twin, the only twin-cylinder machine ever to capture a world title in the 500cc class. It was also not only the first title for AJS but also the last. Despite challenging for World Championship honours and even winning a 500cc Grand Prix in 1954 that was it for AJS. There was also an Isle of Man TT win in the 350cc class in that same year and the single-cylinder AJS 7R was the choice of many Grand Prix privateers throughout the 1960s. But there were no more World Championship titles.
Its success may have been short-lived but the 500cc parallel-twin double overhead-camshaft AJS engine, both in its original 1949 form and its final development in 1954, is still the rarest and most exotic of the works racers entered by British factories in the entire history of the World Championship Grand Prix racing.
The engine originated in 1945 during the dying days of World War Two as a supercharged design, under the E90S factory reference – ‘E’ for Experimental and S’ for Supercharged.
But why use the ‘90’ designation? That was because the bike was originally going to be raced under the Sunbeam badge, recalling that company’s successful TT-winning Model 90 works racer of the 1920s.
Sunbeam was at the time one of the brands owned by Associated Motor Cycles which, after a 1931 takeover, also owned AJS. AMC itself was owned by the Collier brothers, Charlie and Harry who were Isle of Man TT racers in its earliest days on the Matchless motorcycles that they built at Plumstead in South London. Charlie, in fact, won the 1907 TT on a Matchless and repeated that success in 1910.
They had disposed of the Sunbeam brand when BSA came shopping for the company’s business bicycle in 1943 and bought the motorcycle manufacturing rights as well. Otherwise, Sunbeam might have gone down in history as the first World 500cc Champion!
The AJS E90S project was ironically the brainchild of legendary Norton race engineer Joe Craig, who had joined AMC briefly in 1939, in the wake of Norton’s decision to concentrate on producing military bikes for the coming conflict, at the expense of racing. At AJS Craig was tasked with planning a post-war replacement for the very fast but unreliable and scary-handling supercharged V4 AJS and had originally dallied with an in-line blown triple before settling on a twin in 1942.
Craig’s original design to replace the complex V4 was for a supercharged parallel twin with near-horizontal cylinders that had 100-degree valve angles and hemispherical combustion chambers in the cylinder heads to optimise combustion. This layout would have allowed a gear-driven Roots-type blower to be positioned in a cradle above the gearbox of the unit-construction engine which, like the AJS-designed pre-war V4, would also have been water-cooled to combat the higher running temperatures of forced induction.
The shock 1946 FIM ban on supercharging, however, meant that the E90S had to end up becoming the AJS E90. The bike’s overall designer Vic Webb carried on engine development with Craig, largely in their spare time but with the help of Australian Phil Irving (the Vincent design guru who was then working for AMC) they had to hastily convert the design to an air-cooled, atmospheric induction format.
The redesign had domed pistons and a very different cylinder head with 90-degree valve angles, that featured the distinctive spiked finning which gave rise to the ‘Porcupine’ nickname. In this form, the AJS 500 twin only delivered a mere 29bhp when first run on the AMC dyno in 1946 – which was perhaps why Craig returned that year to Norton, to head up the AJS race team’s main rivals! But by the time of the bike’s debut in the 1947 Senior TT, power output had increased to 37bhp at 7,600 rpm, running on the low 70-octane pool petrol of the time.
Spiked finning between the cam-boxes and over the combustion chambers immediately resulted in the ‘Porcupine’ nickname
In fact, the E90’s arrival on the Island had been a race against time, with the existence of the bike only revealed to the press at a May 1947 press conference. Just one week earlier, AMC sales manager and works rider Jock West (a pre-war GP-winner for the works BMW team and who had finished second to Georg Meier in the German team’s 1939 1-2 victory) first rode the bike down the A2 Maidstone by-pass, before it was packed up and taken to the Isle of Man for its race debut!
Given the lack of testing, the performance of the AJS riders aboard the untried E90 in a race dominated by Craig’s Norton team was at least promising.
Les Graham flat-out down Bray Hill in the Isle of Man Senior TT
Les Graham was in fourth place when he fell off, before first remounting and then finally pushing in with a thrown drive chain, to finish ninth. Jock West had suffered clutch slip from the start but after pitting for adjustments he lapped within three seconds of the fastest lap on the way to an eventual twelfth place.
That initial promise was confirmed by Ted Frend’s victory for AJS in the 100-mile Hutchinson 100 at the Dunholme Lodge airfield circuit in Lincolnshire later that year and Jock West’s third place in the Ulster Grand Prix on the old Clady circuit with its seven-mile straight!
In 1948, development continued with West third this time at Assen in the Dutch TT, from which he had retired with engine problems in the previous year’s race. He was then second the following weekend in the Belgian GP, where the Porcupine’s undoubted turn of speed showed to good effect on the ultra-fast Spa-Francorchamps circuit.
All three AJS riders had retired from the Senior TT on the Isle of Man, but Graham finished third in the Ulster GP before a works Porcupine set a total of 18 world records on the steeply-banked speedbowl at Montlhéry in France in November. It was a good omen prior to the introduction of the first-ever motorcycle World Championships the following year.
That inaugural six-race series in 1949 saw history-making success for the AMC works team – Les Graham winning the Riders’ title, and AJS the Manufacturers’ crown.
Les Graham won the 1949 Swiss GP on the cobblestones of Bremgarten
This came after a poor start to the season, when Graham led the Senior TT for almost the entire race, before once again breaking down on the last-lap run to the flag (this time with a broken magneto drive). He coasted downhill to the final corner at Governors Bridge for more than two miles and then pushed the hefty bike for a quarter of a mile along Glencrutchery Road to finish tenth.
But after the TT frustration, Graham took victory in the Swiss GP on Berne’s gruelling cobblestoned Bremgarten circuit, to record the AJS twin’s first GP win..
It was a success he repeated later in the season in the Ulster GP, with Doran and West fourth and fifth and in the meantime, he had finished second to Pagani’s works Gilera four at Assen, before retiring with a split fuel tank in the Belgian GP at Spa, which was won by his AJS teammate Bill Doran.
Even so, because only a rider’s best three results counted in the final points table, Les Graham had done enough to win the inaugural 500cc World title for the British marque.
Words by Bruce Cox
