G45 Matchless: The temperamental twin

Bike Profile

Ray Armstrong's restored Matchless G45/209.

Story: Jim Scaysbrook • Photos: Keith Ward, Dennis Quinlan, Keith Bryen, Jim Scaysbrook

“The G45 was very simply a touring motorcycle, anything but inspiring.” These are the words of Australian international racer, the late Keith Bryen, describing his mount for the 1957 Isle of Man TT – a works-supplied and fettled version of the twin cylinder production machine. 

The G45 Matchless was a hybrid of the chassis from the AMC company’s successful 350cc AJS 7R, fitted with a highly-tuned and modified version of the 500cc pushrod twin Matchless G9 engine. The concept for the G45 was rather surprising from the beginning. Given the success of the AJS 7R since it first entered limited production in 1948 as a welcome option to the Manx Norton for the 350cc Junior class, it had long been expected that Associated Motor Cycles (owners of AJS and Matchless) would simply bore and/or stroke the single overhead camshaft 350 to produce a 500cc version. In fact, several enterprising privateers did exactly that to come up with capacities ranging from around 370cc to just over 400cc. The limiting factor on the 7R was the long bolts securing the head and barrel to the crankcases – the spacing of which limited the diameter of the cylinder sleeve which protruded into the crankcases. The AMC factory may well have considered the idea of a ‘big 7R’ but instead decided to fit the G9 twin engine, with its three-bearing crank and separate barrels and heads (meaning one half of the engine could be dismantled without disturbing the other). The factory’s reasoning behind the decision was that the G45 would provide publicity for the company’s 500cc twin (sold as either the Matchless G9 or AJS Model 20).

The G45 featured here – engine number 209 – was the machine originally owned by Bob Brown, who collected it from the factory in London in early 1955.

Inside the AMC Race Department at Plumstead, London, a 1951 7R chassis was adapted to take the twin-cylinder engine. On the prototype G45, entered simply as a Matchless and raced to 4th place in the 1951 Manx Grand Prix on the Isle of Man by Robin Sherry, the deeply finned barrels were cast in aluminium alloy, as were the heads, with the four rocker boxes (also with horizontal finning) in electron. A forged steel crankshaft with shrunk-on flywheels and a racing profile camshaft was fitted. The cam followers had roller ends operating on needle roller bearings carried by hollow spindles, with short two-piece alloy push rods. 10.0:1 high compression pistons, larger valves and triple valve springs completed the package. Sherry was lucky to finish the Manx GP, as one of the pillars supporting the rockers broke on the final lap, although he limped to the finish. This form of failure would become commonplace on the G45 – many engineers reckoning that the rocker failures were caused by the camshaft’s fierce design, necessitating the use of extremely strong valve springs. The special alloy pushrods also gave trouble, and valve float resulted in the collets jumping off the valves with subsequent disastrous results. The rest of the engine, including con rods, oil pump, timing gears and main bearings were all standard G9 items.

The engine was also not as straightforward a fitment to the 7R chassis as AMC may have liked. In order to line up the primary chain with the existing magnesium Burman close ratio gearbox as used on the 7R, the twin cylinder engine had to be mounted off-centre in the frame by around one inch, giving the bike a slightly lop-sided appearance when viewed directly from the front. The frame was also modified on the left side, below the swinging arm pivot, where the lower frame rail had to be cut and cranked inwards to clear the left side exhaust pipe and megaphone. 

On Sherry’s Manx Grand Prix machine, a single carburettor was fitted, mainly due to the problems associated with fitting twin carbs under the standard 7R fuel tank. This soon gave way to twin carbs mounted on long inlet stubs with the fuel tank scalloped out under the rear section to provide space.  The prototype G45’s next major outing was at the 1952 Isle of Man TT, where it was ridden by Australian Ernie Ring, who battled with clutch problems before crashing on the fifth lap. At this time, the AMC factory’s efforts in the Senior class were still focussed on the complex DOHC Porcupine twin, and the G45 received little attention. Ring did much of the development work on the G45 (assisted by West Australian George Scott), as well as test riding the AJS Porcupine, mainly at the Snetterton circuit north of London. 

Australian Ernie Ring on the prototype G45 in the 1952 Senior TT.

Later in 1952, the G45 was trotted out again for the Manx Grand Prix, and this time it won in the hands of local Derek Farrant, who established new race and lap records. It was a popular, if somewhat controversial win, as the Manx GP rules strictly banned factory ‘works’ models or prototypes. AMC argued that the G45 was actually just a ‘customer’ 7R with a G9 engine, so the result stood. The success encouraged AMC to exhibit the G45 at the Earls Court Show in November 1952, with the announcement that a limited number would be produced for 1953 at a price of £366 including UK purchase tax – a hefty £93 more than a 500cc Manx Norton. Officially, the G45 produced 48 horsepower at 7,200 rpm, and woe betide the rider who exceeded that rev limit! As displayed at the Show, the G45 had 21-inch front and 20-inch rear wheels – the same as the 7R – but by the time production commenced in 1953 (with the engine number series beginning at 100) these had been changed for 19-inch front and rear. The most obvious change to the production versions was the use of the new frame with the engine cradle tubes much closer together, so that the exhaust pipes now sat outside the down tubes.

It was the season-opening meeting at Silverstone in April 1953 when the first of the new machines was delivered to eager UK owners. Two months later, 12 examples started in the 1953 Senior TT, but all bar three retired – most with valve gear problems. At the TT, which opened the 1953 World Championships, Ring again rode the ‘prototype’ G45 but once again failed to finish. For the following Dutch TT and Belgian Grand Prix, the AMC factory provided Ring with an AJS Porcupine for the Senior class, and agreed to loan the G45 to George Scott. In his first ride on the twin, Scott amazed everyone by setting fastest 500cc time in the non-championship race at Nurburgring, Germany, although he retired with clutch trouble in the race. At Tubbergen in Holland, George had pushed the unfancied Matchless into second place on the final lap of the 500cc race. Attempting to pass fellow Aussie and future 350cc World Champion Keith Campbell, he lost the back end (which was coated in oil from a split oil tank) and crashed heavily, knocking himself unconscious. The completely wrecked Matchless was delivered back to the factory in London in three pieces and scrapped. 

Keith Stewart’s brand new G45 on arrival in Sydney in 1954.

For 1954, G45 production was stepped up a notch and a number were exported to Australia, New Zealand, and South Africa. A few were even rebadged as “AJS 10R” and supplied to the AJS agent in Venezuela. Around five went to New Zealand where they were ridden by Len Perry, Selwyn Burt, Peter Murphy, Bill Collet and Leo Simpson. It was in New Zealand where the G45 probably scored its major successes, which included twice winning the New Zealand Grand Prix at Mangere. At least one went to Western Australian for Peter Nicol to ride, one to Tasmania for Peter Ricketts, one to Queensland to be purchased from Markwell Bros by Royce Nixon, and two to NSW Matchless distributor A.P. North which were sold to Keith Conley and Keith Stewart. Both these riders achieved considerable success, although Stewart’s machine was severely damaged in a crash at Mount Druitt in May 1955. Stewart’s injuries was severe enough to force him to retire from racing, and the G45 was sold to George Colley, who rode it as a solo for a while before converting it to an outfit, which was ridden by Brian Thomas, with Colley in the sidecar. The machine still survives in Sydney. In early 1955, Victorian Matchless agents Milledge Brothers imported a G45 which was sold to Tasmanian Bill McGregor. Around 1960, Victorian Ron Robinson acquired the ex-Royce Nixon G45, which he rode quite successfully until he left for Europe in 1963. In addition, several well-used examples came back from overseas with Bob Brown, Allen Burt, Ritchie Thompson and possibly others.

Four G45s after the 1955 New Zealand TT at Mangere. Left to right: Bill Collet (2nd), Len Perry (6th), Peter Murphy (1st) and Leo Simpson (5th).

The G45 ridden by Keith Bryen in the 1957 Senior TT was the final incarnation of the model. AMC had finally been persuaded to abandon their universally despised ‘Jampot’ rear suspension units in favour of Girlings, but in other respects the G45 was basically unchanged from its 1953 specification and hopelessly outclassed against even the production Manx models. Having raced Nortons for his entire European career to that point, Bryen was highly unimpressed with the G45, which in its 1957 form was reputedly putting out 52 horsepower at 7,400 rpm. The cylinder heads had been slightly redesigned for 1956, supposedly giving better gas flow.

Estimates vary, but most experts agree that less than 80 G45s were produced between 1953 and 1958, the final year for the model. In 1958, Matchless finally did what it should have done in the first place – produce a ‘big’ 7R which appeared in the TT that year in prototype form, ridden by Australian Jack Ahearn. The G50 was further developed over the next six months by Ahearn, Harry Hinton Junior, and John Holder, and went into limited production for the 1959 season. 

Bob Brown on the cobblestones at Sachsenring, 1955.

When local star Bob Brown made the move to Europe in 1955 along with his mate Allen Burt, the pair purchased a new 7R AJS and G45 Matchless each. Burt was badly injured at the TT and spent almost a year recovering, but Brown quickly established himself as a fast, safe and consistent racer, and at the 1955 Dutch TT, scored a brilliant fifth place in the Senior race. Two months later, Brown brought his G45 home second in the Ulster Grand Prix, with Kiwi Peter Murphy behind him. This was ever to stand as the best solo result ever achieved by a G45 in World Championship competition (although Pip Harris finished third in the 1955 Isle of Man Sidecar TT). 

Twin Amal GP carbs.
Like the 7R AJS of the period, the G45 uses a magnesium-case Burman gearbox.
The Australian penny fitted to the G45 by Bob Brown in place of the usual Matchless badge on the drive side crankcase.

The G45 featured here – engine number 209 – was the machine originally owned by Bob Brown, who collected it from the factory in London in early 1955. Brown raced the G45 for the 1955 season and continued with it for the 1956 season, where his mechanic was Allen Burt, who recalled replacing the exhaust valve countless times after it had shed its collets. At the end of the 1956 European season it was brought back to Australia and left with Ross Pentecost – who was closely connected with the Matchless brand in Sydney and had a small business buying and selling bikes and spares – to be sold. It took a while to unload, and Pentecost rode the G45 a few times before it finally found a new owner.  After passing through a number of hands it was acquired by Jack Saunders who at one stage fitted a Triumph engine and later raced it in in the early days of Historic Racing in Australia. 

Shortly before Jack Saunders died in 2012, the G45 was sold to Queenslander Ray Armstrong, a man with a strong passion for the model. Jack was not known for his immaculate presentation, and the G45 was certainly looking its age by the time Ray acquired it. The bike was completely dismantled and while Ray tackled the restoration of the cycle parts, the engine was sent to David Blomfield for a total rebuild. “David lives in the mountains near Mudgeeraba and with all the bushfires, I was extremely nervous until I got the engine back,” says Ray. “It was more than just a rebuild. Jack had the bike on coil ignition so I had to get the correct magneto as well as an oil tank. To fit the battery for the ignition, Jack had cut a rough hole in the oil tank and the tank couldn’t be reused. The rear frame had been hacked about to fit conventional rear units, rather than the Jampots which have clevis mounts top and bottom, so that had to be fixed. But there were some good points – like the rims which are the original Dunlop alloy, very rare. Genuine G45 petrol tanks are also rare – they have an identifying number stamped on the filler neck – and they are different to a 7R which not many people know about.”

Jack Saunders with the G45 now owned by Ray Armstrong in the pits at an Historic meeting at Amaroo Park in the late ‘seventies.

Since completing the restoration of G45/209, Ray has acquired G45/197 – the ex-Elmer McCabe model with its distinctive ‘Porcupine’ style pannier fuel tank. He also has another one –frame number G45/2011 – disassembled but with enough genuine parts to complete a full restoration. “I get requests all the time to sell these parts, but I am reluctant to do so because they tend to end up being used for the wrong bikes. There are plenty of G45s around that have been cobbled up using G9 engines, 7R frames and other incorrect bits, and I want to prevent that sort of thing happening if I can.”

However, Ray says he is prepared to part with one or both of the complete bikes, for the right price. “We’re only custodians after all, and there are things I still want to do, so if I got the right offer I would sell.” Ray can be contacted on 0439 831 171.