The thin end of the wedge
The 250cc, or Lightweight class, was in a state of flux as the 1960s dawned. In Europe, works bikes from MV, MZ, Morini and Mondial ruled the roost in GP racing, but there was precious little fodder for the privateer. Many still relied on ancient British four stroke singles and scrambles-based two strokes like Greeves and Cotton, and there was the emerging force from Spain led by Bultaco. In Japan, Yamaha had a 250cc road machine, the twin-cylinder engine of which had strong links to the German Adler, including several of its inherent faults. Yamaha produced the YDS1 in 1959, and soon after began offering racing kits for sale. The road-race kit (there was also a ‘scrambles’ package) effectively replaced the entire top half of the engine, as well as the ignition system, with bigger carburettors and expansion chamber exhausts. The tuned YDS1 poked out around 25 horsepower at 9,000 rpm. Yamaha’s next step was the YDS2, introduced in 1962. Again, a race kit was offered but on the track, the Yamaha’s roadster heritage was still a disadvantage.
A dedicated racer was needed, and in late 1962, the first of the TD1 series, officially listed as the TD1-A, was displayed at the Tokyo Motorcycle Show. Although still based on the YDS2 lineage, the TD1-A incorporated, for the first time, a frame expressly made for competition. The forks and brakes were also specially-made items, but despite the attention to detail, the handling was significantly behind European standards.
The engine too had come under intense scrutiny by the factory boffins, but in one respect was doomed to ignominy. The YDS2 (nee Adler) design had the clutch mounted on the crankshaft, running at engine speed. The shaft itself was of only 20mm diameter, and a missed gear or even an overly-energetic getaway could snap the shaft, sending the clutch flying through the outer casing. This design not only led to repeated crankshaft failure, but severely restricted the choice of gear ratios. On the TD-1A, internal ratios were the same as the YDS2 road bike, with the exception of fourth gear – meaning that first gear was unusable for anything but starting. Alloy cylinders with Nikasil-plated bores and an improved alloy mix for pistons improved top-end reliability markedly.
The crankshaft-mounted clutch was probably the most significant in a considerable list of flaws that dogged Yamaha 250 racers right up until the introduction of the ground-breaking TD1-C in 1967, when the clutch was finally moved to the gearbox countershaft where it belonged. Of the estimated production run of 60 TD1-As, three are extant in USA, and three are known to exist in Australia. All these were imported by Victorian Yamaha distributors Milledge Brothers in November 1963. Two were retained for their supported riders Allan Osborne and Ken Rumble – it was Rumble who had scored Yamaha’s first Australian title when he won the Australian 250cc Short Circuit Championships at Campbellfield in 1961 on a YDS1-R. The third TD1-A was sold to Tasmanian star Ike Chenhall. The price was £495 ($990); slightly more than the final examples of the Manx Norton of the same year.
The motorcycle featured here was the example sold to Ike Chennhal. Aboard his new and expensive pride and joy, Ike was immediately competitive at the local circuits Symmons Plains and Baskerville, and especially so at the once-a-year public roads event at Longford, where the long straights suited the Yamaha well. Occasionally, Ike would share the bike with fellow Launceston rider Ian Tilley, who always gave a good account of himself as well. By 1969 the Yamaha was uncompetitive and troublesome, and was sold to the Tasmanian Yamaha distributors, whereupon it passed through various hands before vanishing from the scene. What is known is that the original engine suffered the inevitable crankshaft failure and was unceremoniously consigned to the local dump – replaced by a roadster YDS3 powerplant. The eggshell-thin alloy fuel tank was also scrapped, but virtually everything else was retained as the TD1-A carried on a less conspicuous life as a club racer. For most people, the Chenhall Yamaha was but a distant memory by the time it appeared as a lot at Tulloch’s Auctions in Launceston in 2002. There were few bidders for the tatty looking old racer, but John Rettig, a Hobart-based former successful rider, knew what he was looking for – and a bid $2,000 secured it. John had done his homework and had identified chassis number T1-077 as the famous Chenhall bike. The frame still carried the extra lugs above the footrests where Ike had fitted a cross-over shaft to swap the gear change from left to right.
Thus began an 18-month rebuild that involved Rettig in a global search for the missing bits to restore the TD1-A to its former glory. Miraculously, considering the rarity of the model, a brand new petrol tank was found in the USA, and a complete, if well-used bottom half of an engine also came from the States. The original TD1-A cylinder barrels were plated using the Porsche-developed Nikasil process, and a lengthy search turned up a pair in Australia, along with a set of cylinder heads. The carburettors, British Amals made under licence in Japan and fitted with remotely-mounted Mikuni float bowls, came via Perth-based Yamaha expert Les Hawkes, who has a collection of early racers (including a TD1-A) himself. The handlebar levers, unique to this model, had to be individually cast and machined.
The Rettig TD-1A is a fascinating reminder of the bike that started the 250 class revolution more than 40 years ago. Yamaha, to its credit, learned quickly from its mistakes and every subsequent model was an improvement on the previous one. Within ten years of the TD1’s introduction, grids worldwide were totally dominated by the Yamaha twins in their various forms. With the British tackle gone and Italian racing lightweights scarce, you can only wonder if road racing would have survived at all without the lineage that the TD1-A started.