Yamaha TD1-B
A model history
The Yamaha TD1B had a profound effect on the face of road racing worldwide. Picking the differences in the model’s evolution is not easy.
In 1965 when Yamaha decided to enter the prestigious USA 250cc road-race scene, especially the Daytona 100, they demoralised the competition finishing 1,2,3,4,7,8,9,10. To prove it was not luck, they backed it up in 1966, finishing 1,2,3,4,6,8,9,10. This race-dominating machine was Yamaha’s 250cc TD1B over-the-counter racer, whose two-stroke engine was based on the street 250cc YDS3. Average race speed in 1965 was 91.4 mph; only a few mph slower than the 750cc Daytona 200 class. From this race on, the TD1B was called the “Daytona” in the US.
The Daytona 100 race for 250cc motorcycles was introduced in 1963 on the new dedicated race circuit with the 1963 and 1964 races being won by Harley-Davidson, who then owned Aermacchi in Italy and used their race bike which was based on the 250cc Sprint road bike. By the American Motorcycle Association (AMA) rules the engines in the 100 and 200 classes had to be based on street motorcycles so Yamaha’s TD series race bikes were built specifically to compete in the AMA races and were all based on the two-stroke street YDS series motorcycles. This was an important criterion for Yamaha as two-stroke engines were viewed by the buying public as slow, unreliable, smelly engines only fit for small ride to work bikes, with Honda promoting the virtues of four-strokes. If Yamaha wanted to stay in business by proving their products’ performance and reliability then not only winning but utter domination was paramount.
Yamaha released their new YDS3 with AutoLube oil injection in mid-year 1964 and it was an immediate success in the USA. The TD1A race bike already existed so it was just a matter of substituting the YDS2-based motor with the YDS3based motor. Yamaha used both the racer and street bike to improve performance and reliability, so all the weakness of the YDS2/TD1A were rectified for the YDS3/TD1B. AMA’s street bike rule primarily centred around authentic crankcases but other components could be changed or modified so aluminium racing cylinders (YDS3 were cast iron) and heads were fitted, a couple of gears were changed to produce a close ratio gearbox, a magneto, remote float bowl carbs and other minor racing parts were also added. Standard road bike parts included not only the crankcases but also the crankshaft and many transmission components, illustrating the robust nature of the street bike. As the YDS3 was being released the race department was developing and building the TD1B, shipping
100 of the first batch to the US by November 1964 in preparation for the 1965 Daytona 100. Northern hemisphere countries’ summer is their racing season and starts in March but TD1Bs were already on the race circuits in sunny California with Yamaha USA factory rider Tony Murphy winning the Willow Springs 250cc 75 mile race. When Cycle World tested both Tony’s and a straight-out –of-the-box TD1B in March 1965 they wrote, “We were considerably impressed with the performance of the TD1B; it was very fast and won the 75 mile road race on a course that is definitely not kind on engines, without missing a beat. It became obvious that Yamaha has found the reliability to match their 250cc twin’s speed.” The tester did complain about poor handling of the Tony Murphy bike only to find the frame had broken which was a common problem. In the US an “out of the crate” TD1B did not have a fairing. Yamaha found that fairings took an excessive amount of space in the shipping crate so the bikes were sent minus fairing and Yamaha USA had them made using Japanese moulds. ‚
Yamaha were well prepared for their Daytona assault with the first batch of over 100 TD1Bs sold or in dealers’ showrooms. From the introduction of the TD1B, Yamaha was virtually unbeatable in 250cc races taking 13 consecutive Daytona 100 wins with each of these races having more than 80 starters. In 1967 when the TD1C was released, Cycle Guide’s technical analyst, Bob Braverman, wrote a summary on the TD1B saying “It’s been a long time since any racing machine has had the impact on the American racing enthusiasts the way the Yamaha TD1B has.”
And “The rather amazing thing is that most of the engine parts are interchangeable with the street version. Many people have expressed surprise at the straightforward and simple process of maintaining this bike. No critical clearances or special rituals needed.” Both the TD1B and YDS3 Yamahas were also significant because sales rocketed and Yamaha found their production facilities unable to cope as their manufacturing engineering, planning and control was still the old manual system.
IBM had developed the first of the computer Manufacturing Requirements Planning systems with these in use in the US, so Yamaha looking to their future, purchased one. I am sure that some readers who had to replace manual systems with computer MRP systems will know of the immense amount of work, detail and accuracy required and in the case of Yamaha it took about two years. In 1964 the computer system had to be completed before introduction. As existing models were changed virtually
yearly and totally new models released, the length of time taken to introduce the MRP gave Yamaha a problem so model designations were not changed but frozen resulting in three distinct versions of each model but all labelled as YDS3 and TD1B. Normally three different model numbers for the YDS and TD1 series would have been issued but this could not be done creating confusion at the time, which has since been amplified and added to by those who came later trying to explain all the variances creating many incorrect assumptions and myths.
Economics dictated the number of race bikes produced (approx. 120 per batch) and was set prior to commencement with parts manufactured or purchased in one go to cover the build. Unlike production bikes, they were not assembled on a production line to demand, but were quickly assembled as a batch in the race shop and delivered in time for the start of the racing year with bikes being sold until the batch was gone. For this article the versions are loosely described by batch year remembering the 1964 TD1B model was produced in the second half of 1964; so version one 1964 (Ver1), version 2 1965 (Ver2), and version 3 1966 (Ver3). Because of the huge sales success of the YDS3, not only were Yamaha’s manufacturing systems under pressure but so too were their manufacturing processes. From the start of the YDS series’ many parts (including crankcases) had been manufactured using production sand casting which is okay for lower volumes but has many disadvantages as volumes increase. Volumes now dictated pressure die-casting so Yamaha installed a modern diecasting facility. Until mid-1965 the YDS3 crankcases were sand cast and as the TD1B (Ver1) used YDS3 crankcases they were also sand cast but when the die casting facility was commissioned both bikes changed to die-cast crankcases which included the complete batch of Ver2 TD1B.
An organisational change also occurred on the
Ver2 TD1B which resulted in a new pointed tank and squared off seat hump. Until recently Yamaha didn’t have a styling department and from 1955 used a styling studio, GK Dynamics, to style their motorcycles. GK Dynamics was formed in the early 1950s by a group of university students who studied under a very forward-thinking Professor Iwataro Koike who insisted on world class leading concepts, a philosophy that reflected Yamaha’s goals. In recognition of his mentoring the founders named the business “Group of Koike” shortened to GK and have since styled everything from noodle spoons to sky-scrapers and bullet trains. Linking back into the TD1B story, until Ver2 TD1B the race department had styled the race bikes but this task now became part of GK’s responsibilities. GK had styled a number of Yamaha’s street bikes on their “softness and sharpness” design and incorporated it into the Ver2 and Ver3 with the pointed front of the tank and the rounded rear.
New road models also impacted on the Ver3 TD1B. In 1965 Yamaha introduced a new 305cc street bike, the YM1, which although having a different bore and stroke to the 250cc YDS3 was extremely similar to the point where a common parts book was used. Prior to the YM1, the YDS3/TD1B used gearboxes with teeth at a 2mm pitch but the engineers thought that with the extra power of the YM1 stronger gear teeth were required so coarser gears were made with a 2.5mm tooth pitch. As the YM1, YDS3 and TD1B had dimensionally similar gearboxes it was decided to reduce part proliferation by using the new gearbox in the YM1 and YDS3 and redesigning the TD1B Ver3 gearbox to use the 2.5mm pitch gears. Also, Yamaha had released the YDS3C Street Scrambler which was a high pipe on/off road version and made it dirt friendly by fitting a gearbox with different gear ratios. To produce a better TD1B close ratio gearbox, engineers used the YM1 second pinion and third gear, the YDS3C third, fourth and fifth ‚
pinions and fifth gear plus new TD1B cogs and a shaft. As with earlier models the rest of the gearbox was street bike parts. All TD1/YDS3 gearboxes were praised for their strength. Because TD1Bs were built in three single batches the gear pitch change only affected the Ver3.
Many changes were made between versions 1-3. On Ver1 and 2 the exhaust expansion chambers were chromed with solid mounts, both perfect scenarios to induce cracking, but resembling the street YDS3. On Ver3 the expansion chambers changed to flexible spring mounts and were painted “crack resistant” silver, modifications usually attributed to the next model TD1C. On Ver3 the float bowls were mounted from the frame (usually attributed to the TD1C) where-as Ver1 and Ver2 had the float bowls mounted on the rear of the motor which caused excessive fuel frothing with fuel squirting out the overflow outlets which appeared to be cured by the frame mount. Hand levers on the Ver1 TD1B were from the GP racers being pressed steel levers with 25mm rubber balls moulded on the end with unique lever perches. The GP bikes used a double-sided drum front brake and the pressure being applied to each side had to be equalised for effective braking. Inside the pressed steel lever was a pulley which the single brake cable that operated both brakes went around thus equalizing pressure. Brakes on the TD1B were only single sided but Ver1 had the steel levers with Ver2 and Ver3 using the usual aluminium levers. Cylinders were three port (counted by ports operated by top of piston) but tuners found that by grinding a channel between the inlet and transfer ports on each side, two more transfer ports could be created. This was so successful that Yamaha introduced it as standard on the TD1C and the next model street bike, the YDS5, advertising it as “Five Port Power”. Readers who were two-stroke tuners would remember the trick of filing a ramp in the top of the piston corresponding to the exhaust port to increase exhaust lead. The TD1B piston came standard with the ramp from Yamaha. Although the Kayaba front forks were well regarded, they were exceptionally poorly designed with changing the oil seal a major task. However, the main problem was that the fork legs were too close together with the top front fender bolts perfectly aligned to the widest part of the narrow 2.75 Yokohama racing tyre. When a different brand tyre was used or even a tyre 0.25 wider, the wheel could not be fitted which is why most of the TD1B and Cs ended up racing without the front fender. Rear shocks were not replaced by Australian riders but just about all the US riders fitted Girling rear units including the TD1B factory bikes. The frame and brakes had been designed in 1960 and by Ver3 were showing signs of obsolescence and should have been replaced but the marketing guys kept them as they vaguely mimicked the road bike. However, the swinging arm was strengthened which improved handling. The Ver3 rolling chassis was virtually the same as a TD1C.
The TD1B over-the-counter racer was Yamaha’s real racing success story but as the US was the prime market only a handful were exported to the UK, mainly Ver3, which is why in the UK the changes are
not understood, leading to myths. Because Australia was the first export market for Yamaha, Australia received more than the UK. Race bikes are only meant to last one season with parts books being expensive so roughly altered TD1A parts books were used with part numbers being erased and obvious new numbers typed in. Even the final IBM part numbers book (Dec 1967) was not printed until after the production of TD1B’s had ceased with some diagrams still showing the TD1A outline creating confusion to later historians and restorers.
The Myth: Daytona Specials
Myths have a problem of being perpetuated, embellished and embedded as fact as time passes and although strengthening the myth, it does not make it correct. The confusion surrounding the three versions of the TD1B, especially the first batch with sandcast crankcases and the 2mm pitch gears, led a well-known Yamaha UK/Europe author to speculate in 1985 that Yamaha were unprepared to build TD1Bs due to poor planning. Supposedly to meet the Daytona deadline they “cobbled together” some (100) “Daytona Special” TD1B’s using sandcast crankcases “rather than the usual diecast crankcases” which, as explained were not yet in production. In not realising two gear pitches were used, 2mm and 2.5mm, the author concluded that Yamaha had “thrown the gearbox together” installing sets of early YDS3 gears. Continuing the myth, to use up TD1A stock the rounded tank was used on the “Daytona Specials”. Although we know from Cycle World March 1965 that 100 Ver1 had been delivered to the USA by the beginning of 1965 (before Daytona) and other countries such as Australia had also received them, the myth is repeated in many Yamaha race bike accounts, taken as fact and has been changed with Ver1 numbers produced now being incorrectly quoted as only 60 units. Today we have collectors claiming to have a rare Daytona Special when in fact it is just a Ver1 TD1B. The Daytona myth is now taken as “factual” but is a totally different story to what occurred. From Day 1 Yamaha wanted a starting grid and winners circle full of their two-stroke machines and when reading 196264 US magazines it was obvious that Yamaha USA were methodically working towards this with factory bikes and Japanese mechanics. A number of TD1As were continually winning 75/100-mile events across the US with Yamaha-backed riders. Yamaha knew the TD1B could dominate Daytona using out-of-the-crate bikes and hence the 100 Ver1 for Daytona. Yamaha’s future was dependent on the USA market and as top priority this is where the majority of the three versions went. Builds of each version were approximately 120+ bikes per batch and to ensure they were quickly sold the TD1B was priced for Joe Average at AUS$1250 (1966) which was about double the price of the street counterpart but the same as 650cc road bikes. Both the TD1B and YDS3 achieved Yamaha’s goals and were the upward turning point for street and race bike sales world-wide.
The two TD1Bs featured are owned by the author. The yellow-framed Ver2 was raced in South Australia in the late 1960s and was purchased in 1975 as is, with the Ver1 racing career unknown, being purchased in 1985 and restored by the author. The Ver1 originally came with a kickstart but it was common to remove it.