Seeley G50
With the threat of the two-strokes gathering pace, It took some smart thinking and quality engineering to give the British singles a new lease of life in the late 1960s 500GP class
The late Colin Seeley, who passed away in January 2020 aged 84, was a pivotal force in the close-fought British short circuit racing scene of the 1960s, originally as a Gp-winning sidecar driver, then a top-level chassis manufacturer. He went on to become the builder of ultracompetitive complete race bikes and engines, which extended the life of the British single in 500GP racing until 1971, when Tommy Robb twice put his Seeley G50 on the rostrum, in the Swedish and Ulster GPS, en route to seventh place in the final points table. It would be the last time a British single would finish in the top ten of any road racing world championship.
Seeley’s first road race came aged 18 in a one-hour event at Brands Hatch in 1954 aboard a 500cc BSA Star Twin, before giving up an engineering apprenticeship to open a motorcycle shop in Belvedere, Kent in 1956, as a dealer for AJS, Matchless and Greeves.
By 1958 he was racing off-road in scrambles for Greeves, before returning to road racing in 1960, but with three wheels rather than two. Bolting a Canterbury sidecar to a Matchless G50 race bike, he competed in local meetings at Brands Hatch, Crystal Palace and Lydden, before making his Isle of Man TT debut in 1961 – his first Grand Prix event, in which he and passenger Wally Rawlings finished sixth, barely one year after he first raced a sidecar. From 1961 to 1966 Seeley raced in the British and World Sidecar Championships, originally aboard his own machines with Matchless and Norton engines. Eventually, he swapped the single-cylinder Matchless for a flattwin BMW Rennsport outfit, with which he won the 1964 Dutch TT at Assen and finished third in the world championship, after scoring a second-place finish in the IOM Sidecar TT. In December 1965, without any previous experience of designing or building solo motorcycle frames, Seeley obtained eight Matchless G50 and four AJS 7R race engines from the nearby Amc/associated Motor
Cycles factory, with the intention of building a small batch of solo race bikes. “I wanted to generate some income to help finance running the BMW Rennsport sidecar, which was very costly to race,” said Seeley. “I never thought this would become such a major part of my life for the next eight years – it just seemed a good idea at the time! I had no idea what kind of race frame I would build – I just wanted to make something that was lighter and simpler than the original AMC one, which people would buy. All I had was an acetylene welding set, so I must have been pretty fearless, or more likely bonkers – but I went into the project quite optimistic that I could produce something worthwhile.”
Using the basic chassis geometry from friend Sid Mizen’s standard G50 Matchless, Seeley sketched out the makings of a frame, which he then created entirely by hand, using a primitive plumber’s tube-bending set with formers up to 1¼in in diameter, secured to a heavy steel bench cemented to the ground in his workshop yard. “I remember bending the steel tubes for the Mk1 Seeley Matchless frame,” he recalled. “I’d filled the 1¼in [31.75mm] by 16 gauge Reynolds 531 chrome-moly tubing with silver sand to prevent the tube crinkling as I pulled it around the cast iron former. Suddenly, there was an enormous bang as the former exploded in a shower of bits. It had crystallised in the freezing weather conditions. Not a good start to the grand plan!”
After establishing Colin Seeley Racing Developments (CSRD) to produce and market the frame kits, Seeley realised he needed a top rider to prove the worth of his frame, so he persuaded his near neighbour, five-time British 500cc champion and King of Brands, Derek Minter, to try out the barely completed Mk1 Seeley G50 at Brands Hatch in the February cold, in a same-day comparison with Ray Petty’s Manx Norton – a model on which Minter had achieved all his short circuit success. Fitted with a brand new stock G50 motor, it was the first time the new Seeley frame had ever visited a race track – albeit running in the reverse direction, in preparation for the Hutchinson 100 meeting later in the year. But Minter immediately took to it, describing it as: “The best-steering frame I’ve ever tried”. Minter even turned down an offer from top sponsor Tom Kirby to race his new Metisse-framed 7R/G50 duo in 1966 as team-mate to Bill Ivy after that test, in favour of pairing up with Seeley. It was a decision ‘The Mint’ proved to be correct, when he finished third first time out at Mallory Park on the Seeley G50 behind race winner Ivy, then won the opening race of the season at his Brands Hatch home track, defeating the cream of British short-circuit aces before 30,000 fans lining the full GP circuit, on his Seeley G50. Victory the following weekend on the 350cc Seeley 7R at Snetterton proved the chassis design’s worth, and the orders for replicas began flowing in.
But then a spanner was thrown in the works when AMC went into administration in August 1966, threatening the flow of engines and gearboxes to power the Seeley frames for which demand had skyrocketed, as several riders prepared to switch to them for the following season. But Seeley found a solution – in October, he purchased the manufacturing rights and tooling for the Matchless G50/ AJS 7R/manx Norton GP racers from the bankruptcy liquidators. As he was used to the Matchless G50 engine after racing with one in his sidecar, and his current chassis design catered for that motor, Seeley decided to focus exclusively on that and its 350cc AJS 7R sister, eventually parting with the Manx Norton trademark and engine material to another sidecar driver, John Tickle.
“I’ve never disclosed how much I paid for the takeover of all the AMC racing engine components, jigs, fixtures and drawings – and I’m not going to do so now!” said Colin when I asked him. “But it was a fantastic deal, and I knew I’d never get a chance like this again.” It took two vans and half a dozen men two weeks to move the contents of the AMC race shop from the defunct Woolwich factory to Seeley’s Forge Works factory, just six miles away in Belvedere. “I’ll admit we did get a lot more engine parts than I’d expected!” Colin chuckled.
To give these ageing single-cylinder race engines another lease of life, especially in the hectic hurly-burly of British short-circuit racing where light weight, quick steering and manoeuvrability were crucial, CSRD had produced a much stiffer Mk1 twin-loop chassis of fairly conventional design. The load-carrying upper tubes sloped from the steering head to a point about four inches (100mm) north of the well-braced swingarm pivot, with smaller-diameter tubes forming the rear subframe. These frames were made from Sif bronze-welded Reynolds 531 chromemoly tubing, and carried twin Girling shocks and 18in wheels, originally with cut-down Norton Roadholder forks. “My main focus was directed at saving weight, while ensuring the bike sat lower, and steered and handled properly,” explained Colin. In due course, Seeley’s own forks and brakes – first drums, then discs – were developed, with a lighter Mk2 version of the frame introduced for 1967, made from slightly narrower-gauge 11/8in (28.60mm) diameter Reynolds tubing, with the twin front downtubes set further apart for greater accessibility and extra stiffness.
Colin Seeley retired from racing himself after a third-place finish in the 1967 Sidecar TT, in order to concentrate on building up CSRD. Seeley-framed machines were soon the race bike of choice for GP privateers, as well as so many of the hard chargers in British short-circuit racing, who were racing week in, week out in front of massive crowds up and down the country – and one of them carried Dave Croxford to the Seeley team’s first British 500cc title in 1968.
TOMMY ROBB ‘A GOOD G50 OR MANX ENGINE WOULD LAST YOU THE WHOLE SEASON OF RACING’
“Dave Croxford was our main rider for five years, and brought us heaps of success,” said Colin. “He was a super guy to go racing with, with never a bad word, and always tried his hardest.” In GP racing Seeley G50s finished third, fourth, sixth and seventh in the 1969 Senior TT, with sixthplaced Ron Chandler taking time off from his day job as a Thames lighterman to finish eighth at Assen, fifth at Spa, and sixth again in both Ulster and Monza, to place seventh in the 500cc World Championship. Two years later, Tommy Robb was the second-last single-cylinder rider to climb a 500cc GP podium, when he finished third at the 1971 Ulster GP aboard a Seeley Matchless. Five weeks on, Finn Kaarlo Koivuniemi scored the single’s final GP top three when he rode his Seeley G50 to second place at Jarama.
Of course, there were advantages to running a big single instead of a fragile two-stroke. While Jack Findlay, Keith Turner and the other two-stroke riders spent every moment off the bike changing engine parts and fiddling with ignition and jetting, Robb could sit back and soak up the rays. “A good G50 or Manx engine would last you the whole season,” said Robb. “Halfway through the season I’d take the engine back to Colin Seeley and if he thought it needed new piston or valves he’d fit them.”
But by 1968 the Seeley 7R with chain-drive sohc was coming under increased pressure for 350cc short circuit supremacy from the lighter, nimbler ohv Italian Aermacchis, so Seeley developed a lightweight Mk3 version of his frame design, this time with the front downtubes deleted and replaced by twin tubes which swept straight back from the steering head to the swingarm pivot. The gearbox and crankcase were bolted to massive duralumin engine/gearbox plates, with the forward-inclined motor supported by a bracket joining the cambox to the upper frame tubes.
Fitted with a single-sided drum brake and narrower rims, chain and sprocket, plus as much magnesium in the engine as possible, the result weighed 259lb (117kg) including a full fairing – 21lb (9.5kg) less than the previous Mk2 bike, and far lighter than a standard-framed 7R/G50 scaling 290lb (132kg) unfaired. It was sufficient to put the Seeley 7R back in contention – though not for long, with the 350cc Yamaha two-stokes on the horizon, including the ultrasuccessful Yamsel 350 which Colin created for established Seeley customer John Cooper, whose success with it spawned many orders for replicas.
“To be honest, the main reason for the Mk3 was that it was easier and faster to produce, so that we could actually make some money when we sold them!” Colin admitted. “But it was also quite a bit lighter, simply because there was less metalwork in the design, which did also make it easier to get the engine in and out if you were working under pressure at a race meeting.”
Inevitably, this Mk3 Seeley frame was adapted to use with the bigger G50 motor, bringing Croxford and Seeley a repeat British 500cc title in 1969, with Dave now riding for the South London Gus Kuhn dealership owned by Colin’s mate, Vincent Davey. But Crox was unable to make it three in a row in 1970, with Peter Williams winning the British 500cc crown on the skinny, ultra-lightweight Arter G50 known as ‘Wagon Wheels’, with its cast wheels and Grand Prix Metalcraft chassis. Its design broadly followed the twin-loop duplex cradle format of Arter’s previous Reynoldsbuilt frames, but used slightly narrower-gauge one-inch tubes rather than the 11/8in diameter tubing of the Reynolds chassis. This saved crucial weight, a vital objective for Williams with the reduced power of the bike’s single-cylinder motor versus the multis it raced against in GPS – and the coming wave of two-strokes.
Seeley followed the same path, producing a lightweight
Mk4 version of his frame for Croxford to race in 1971, using the same-gauge tubing but with a thinner wall to save weight. Clothed in a striking bright orange fairing, the new bike scaled just 268lb (121kg) when making its 1971 debut at Good Friday’s Brands Hatch meeting, and scored victory first time out in the 500cc support race to the new UK versus USA Transatlantic Trophy Formula 750 series for Bsa/triumph triples. This was after a titanic battle with Charlie Sanby on the heavier customer Kuhn Seeley, who passed Crox on the final lap, only for the ‘Ruislip Rebel’ to out-accelerate him out of Clearways on the lighter bike, and pip him on the line by half a wheel.
Unfortunately, that was as good as it got for the ultimate Seeley G50, which thereafter suffered a troubled season, with engine problems and simple bad luck restricting its success in both 500cc and oversize 636cc form (which allowed it to compete in the increasingly popular unlimited capacity events). Crox then got collected by a crashing Sanby at the May Mallory meeting, resulting in him sitting out several weeks of racing while he recovered from injury.
In October’s Race of the South on the Brands Hatch GP circuit, Croxford led Giacomo Agostini’s MV-3 for a few laps in the Shell 500cc International before giving best, and ended up fifth after being passed by Barry Sheene’s new Seeley-framed Suzuki, Tony Jefferies’ FATH-URS and Jim Harvey’s G50 Metisse. The times they were a-changin’, and in June 1972 the final two Seeley G50s left the Belvedere factory, though CSRD continued to supply spare parts for engines and frames, until the company was wound up later that year.
During its seven years of operation – during which as many as 25 employees were working at its Forge Works factory in Belvedere before the company shut down in the wake of Seeley’s involvement with Bernie Ecclestone – CSRD is believed to have produced a total of 410 Seeley chassis kits to house G50, 7R, Bsa/triumph triple and Norton Commando engines. It also made the Yamsel frames for the air-cooled Yamaha twins, the 500/750 Seeley-suzukis, including an avantgarde Monocoque version, the Seeley-kawasaki 750 that Paul Smart took to victory in the 1972 Ontario 200, and the frames built for the Ducati factory to house its 500cc and 750cc 90° V-twin engines. Including the handful of seven Seeley Condor G50 street bikes he produced before the shutdown, Seeley also manufactured a total of 76 7R/ G50 engines during that period, many of which are still being used in Historic racing today, and sold more than 40 complete Seeley G50 and 7R racers.
“I always got on well with the Seeley G50s,” says 80-years-young Dave Croxford today, with the wicked smile of someone who knows that’s a massive understatement, after he won two British championships and an awful lot of races on such bikes. “They’d wriggle a bit on the limit, and give you a bit of movement there, but they were much more nimble than a Manx Norton on British short circuits – the Norton was really a bike for the big Grand Prix tracks. But the lightweight version Colin built was his best ever – you could change your line halfway round the corner, if you spotted a gap to get someone on the exit. It was super-responsive and steered like a 250 – I was really upset I never got the best from it because of various engine niggles and being injured for a good part of the ’71 season, through no fault of my own.”
Colin Seeley’s undoubted skills for chassis design came to the fore in harnessing the performance of the decade-old Matchless G50 motor so effectively, and making it competitive for so long – even after the Japanese two-strokes became such a potent threat. But all good things must come to an end, and the eventual demise of the Seeley G50 in 1972 undoubtedly represented the end of an era.
DAVE CROXFORD ‘THE G50s WERE MUCH MORE NIMBLE THAN A MANX NORTON ON BRITISH SHORT CIRCUITS’