Early Race Development - UNDER CONSTRUCTION

During 1958 Yamaha began work on a new 250cc  machine based upon their experiences with the successful YD Racers, later to called the 250S or YDS1. 
Alongside the development of the YDS1 as a new sports model, a plan was being hatched to use this machine as the basis for a new road race machine to replace the YD racer. The new models were launched in 1959 with the YDS1 available as a standard sports machine and also as a Clubmans Road Racer or Scrambler, with the addition of special "Kit Parts". Later on in 1960 the road racer or YDS1R, as it was later known became available in very limited numbers as a race ready machine.  Factory rider Noguchi privately entered a (works) YDS1R in the 1959 Asama races, when Yamaha did not field an official team. 
YDS1R First Factory Photo.jpg
YDS1R First Factory Photo rear.jpg
Above: The first official factory photo's of the YDS1R sent to Sonny Angel in June 1959 (These photos are now in my archive).
Below: YDS1 Clubman Racer featured as in the YDS1 Range Brochure, again from the Sonny Angel archive.
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Top: Sonny Angel shows off his newly built kit parts converted YDS1R, late 1959/early 1960. Later in 1960 he later received 2 x ready built works supplied YDS1R's.
Above: Noguchi competing in the 1959 Asama races.
Below: Pages from the YDS1 Owners manual describing the Kit Parts to transform the sportster into the Clubmans Racer. Note, the manual calls the machine "Asama Clubman Racer"
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Below: Myself demonstrating a YDS1 Kit Parts Racer I restored in the early 2000's at Brooklands Motor Circuit.
In November 1959 the Yamaha factory developed a new racing YDS1 based engine under the code name YX24 250S, designed by a talented Engineer named Hasegawa, who later went on to become the Chief of Yamaha. It continued to adopt some of the YD's technologies such as polished and knife edged conrods, milled cranks, twin mikuni carburettors, magneto ignition and piston porting, but bore and stroke was now set at 50 x 56mm as the YD-B, and some special works engines even featured magnesium crankcases instead of aluminium alloy.  

During 1959, things became very busy in the Yamaha racing department! As well as the "limited-production" YDS1R, the Factory were busy developing new 100% dedicated factory road racers.
Engineers Hata and Naito were developing 125 and 250cc machines based on the disk valve racer which Showa had produced for the 1959 Asama races.

Yamaha quite logically fitted the new YX24 250S engine into a new frame, developed from the old YD-A chassis, which was code named the YX47. New upgraded brakes, sleeker and lighter alloy fuel tanks and seats were also developed along with other more contemporary designed parts. This YX24 250S/YX47 machine became known as the RR or RR 250. A works version was also built with magnesium engine cases (which, if it had been put into full production in keeping with Yamaha's later naming convention, would have been known as the RD24). These piston ported works machines were raced in several Asian events such as the Singapore GP by Wong Fook Kwong and Albert Lim, as well as making an appearance at the 1961 Daytona GP ridden by Fumio Ito and Yoshi Sunako. The bike was finished in Yamaha's chosen colour scheme of the period, black, but with a red fairing and seat was chosen for Daytona and as seen in some advertising. Several US riders such as Dave Buising and Tony Murphy were also lucky enough to trial the bike and give their feedback to the company. Later in 1961 10 customer "race ready" versions of the RR machines were shipped into the US, later to become known as "Yellow Tankers".  Although surprisingly it has recently been discovered by the author that these machines were not originally intended to be supplied in Yellow by Yamaha. 
Original paint found under some Yellow on an original seat unit, clearly shows the Japanese factory originally painted the seat a similar red-brown colour as previous YDs1R fuel tank.   
The rumours were that West Coast Yamaha distributer Frank Cooper chose yellow for the bikes as that was his favourite colour, but perhaps now we can guess why ‘someone’ made a decision to have them repainted… Maybe they (Cooper/Caswell) thought the brown would not be a great selling factor and “Brown Tanker” just didn’t have the same ring to it !
There maybe another answer though, the Daytona bikes were painted with a "red" seat and fairing, although I have never seen a colour photo of these machines, could the red-brown of this seat be the red of a Daytona machine ?  A colourized image below shows a more bluey-red rather than brown, but this could of course be misinterpreted. I'd very much like to find out for sure.
RR seat orig.JPG
RR seat brown yellow.JPG
The above Japanese charts shows the progression of the early Yamaha race models (although not totally inclusive as it does not include models such as the YDS1 Clubmans racer, the YDS2M Ascot etc) . The 250cc range shows the YD-A/YD-B followed by the 250S (YDS1). It is interesting to see the side by side development of the YX24 125cc and YX24 250S of 1959-60, the YX24 (125) went to become the RA41, whilst the YX24 250S became the RR.
The photo above shows the YX18, the first of a new breed of race machine following the YD's,  which led to the RA41, RD48 as well the YX24 250S and RR / Yellow Tanker.  You can clearly see where the TD1 has it's roots.  

The above might well be proven to be correct now, as the author has recently discovered the remains of one of these works RR 250 Daytona machines (THE VERY FIRST YAMAHA ROAD RACER); at least, the frame and wheels. With a works YX24 250S engine and parts I already have, we should be able to bring one of these truly historic and important machines back to life, 

It has also been discovered that the works RR frame is indeed very similar to the RD48 (& YX18/RA41 frame) by the fact that its front downtubes do not have any additional reinforcing on them at the headstock, and this frame that has recently been discovered had suffered and had a bend repaired - which may well be why the subsequent Yellow Tanker and TD1 model frames were all reinforced !    
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Top: The works RR 250 (YX24 250S) listed as Formula 2 at Jahore GP.
Above: #3 Ito on the works RR 250 (YX24 250S) at Daytona GP Feb 1961. (pic courtesy Motorcyclist).
Above: #4 Sunako on the works RR 250 (YX24 250S) at Daytona GP Feb 1961. Note the flat oval number plate, reminiscent of the YD racer fairings. Colourizing this photo shows the red hue of the fairing. 
Below: A Yellow Tanker customer RR 250 bought by Steve Parker. Note the similar fairing, Rumours had it that the 2 X Daytona works machines were left in the US and sold as production machines to fund the teams air fare home to Japan !
Below: 2 great period colour shots of Yellow Tankers from the Sonny Angel archive. 
Bottom: Another great period shot of a Yellow Tanker, believed to be TBC.... 
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As well as the development of their own piston ported machines in 1959, Yamaha had also invested in the new technology of disk valve 2 stroke timing, with their acquisition of the Showa Motorcycle company.  These new disk valved machines were developed side by side with the piston ported racers and hence both styles shared a similar chassis design (YX47) . The 125cc was intially coded YX18 then later YX40 but when completed it became known as the RA41 and the 250cc (which was developed as the YX47 then YX48) became the RD48 and it was these models which shared a common heritage to the previous YD and the RR 250 that Yamaha first entered into the World Championship GPs in 1961. Since working with and inspecting the YD-A engine internals, it is apparent that the crank diameters and method of construction are the same on both the RD48, RA41 and YD-A, this along with the fact that all these engine feature separate crankshafts, highlight the evolution of the RD48 and RD56 machines back to the original "Asama Racer" . 
Above: The works teams RD48 250's and RA41 125's, both look quite similar but can be distinguished by the number of exhaust pipes.  
Below: Factory drawing of the RA41, note the twin disk valve induction.  
RA41 motor.jpg
It should be remembered that 1960 - 61 was a time of great financial burden for the growing company, with the development of several new road models and unfortunate flop of the SC1 scooter and MF1 moped, but Yamaha still managed to put a lot of development into their racing machines. It is a wonder that they could actually afford to race in any Grand Prix at all in 1961, let alone do so well !
The disk valve RA41 and RD48 showed more potential than their humble piston port brothers, so the factory decided to continue to develop these machines purely for their own GP team and develop the piston port machines for a new customer production model. For the 1962 season a new 250cc sports road machine was developed, called the YDS2. Alongside this, Yamaha's first properly Worldwide marketed production race model, the TD1 was offered and quite surprisingly a race ready YDS2R was also available in some markets.  

The '62 TD1 still maintained a frame based upon the previous RR250 and RA41 (YX47) and featured an engine based upon the YX24 technology but was developed into the new YDS2 engine from the YDS1.  As the model chart previously shows, there were 2 TD1 builds, 1 early batch in mid 1962 and a later batch beginning around November 1962, this may go some way to explaining confusion surrounding numbers of actual TD1 numbers!
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Above: Official Yamaha promotional photo's of the TD1, although the machine is not actually a TD1, but an RR250 "Yellow Tanker" in disguise ! This can identified by thinner forks, centre mounted fuel filler cap, rear shocks, lack of proper rear mudguard (no mounts on frame), fixed oil seal boss on front hub & unmeshed brake vents etc. The fairing and seat are new for the TD1 model.     
Below: The same bike, side view which can be compared to the advert below:   The above photo came from the UK and the below from Australia, showing a now common marketing strategy.  
Bottom: The same bike on an a 1964 TD1 advert (which would have been to advertise the TD1A), this time nicely in colour - which if you look closely, allows us to see that under the black paint of the forks where the faring has scraped them, you can clearly see Yellow paint !  This time the bike is fitted with longer pipes which were developed for the 1962 Suzuka All Japan GP.  The colour scheme is that used at the 1961 Daytona GP.
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An official Yamaha advert for the 1964 TD1, but again showing an RR250 or Factory Yellow Tanker, identifiable by lack of rear mudguard, centre mounted fuel filler cap and straight gear lever, other differences include lack of covers on the brake vents and of course a YDS1 based YX24 engine. 1964 would of course be the TD1A model !
Carefully compare the above machine to the TD1 in the below advert and you will notice lots of small differences, including; The TD1 gained sturdier front forks, meshed brake vents, fuel tank filler cap was moved further forwards and became a screw on type, fuel tank gained fixed fuel taps, the addition of a rear splash guard behind the carburettors, a more curved gear change pedal, a solid rear brake stay and drilled front brake stay. Other changes included the engine being YDS2, improved float chamber brackets and of course the expansion chambers on the 2nd batch of TD1's.    
Above: Yamaha entered their works TD1's in the 1962 Suzuka All Japan races. They won decisively in the Junior Class, beating the might of Honda. Note these late batch bikes have long expansion pipes.
Below: The first TD1's entered the UK in November 1962. The first 2 machines were imported initially and bought by Geoff Monty, who became the 1st importer. Then another machine was ordered at Monty & Wards in December 1962 by Mr Robin Denny. The machine was delivered in May 1963 and subsequently went on to win an International race at Snetterton followed by the Norwich Trophy, becoming the first Yamaha to win a major race in the UK. Note, this machine is identical to the machines above at Suzuka.   
Above: After a crash at the "Bombhole" at Snetterton Mr Denny's TD1 suffered from bent forks and a destroyed fuel tank. Mitsui were semi-sponsoring Mr Denny and he eventually got a set of new type (TD1A) forks. The engine tuning was sometimes supported by "Mick" Nakamura.  
Below: The same bike in 1998, by this time it had gained several modifications, but still retained the same replacement fuel tank.    
Above: The TD1 reunited with Robin Denny (note wrong fuel tank)
Below: The ex-Denny TD1 (T1-052) after restoration by myself.
Bottom: And finally myself giving the TD1 a run around the IOM ciruit in the TT2006 Lap of Honour. (Keigs)
Strangely, even though the TD1 was developed, produced and marketed, Yamaha continued to supply a race ready variant of the standard sports model, in the case of the 1962/63 range the YDS2R was available alongside the TD1, YDS2CM. YDS2M. and standard YDS2 models.
A YDS2R production racer circa 1962/63

Picture credits :  Sonny Angel, the ACU, KEIGS IOM,  Yamaha Motor, Robin Denny, Richard Tracy, Lyn Garland.  

Model Chart courtesy of Ferry Brouwer.