These machines are mentioned on EARLY RACE DEVELOPMENT pages, but they could not be omitted from any history of Yamaha at Daytona.
After the 1958 Catalina Grand Prix, Yamaha maintained a presence in the US by sponsoring local riders racing out of their base at Marty's Foreign Motorcycles in California, as mentioned on the CATALINA GRAND PRIX pages of this site, mostly competing in the West Coast. It wasn't until 1961 that Yamaha sent over another team of new machines and riders from Japan, this time for the US GP which was to be held at Daytona in February of that year.
The new machines were the direct descendants of the Catalina YD machines, with the engines code named YX24 250S and the frames YX47, they together made up the machine known as the RR or RR 250.
Initially, the works machines were produced with frames almost identical to its disk valve counterparts, which were a development of the YD and first seen on the YX18 (Yamaha's first dedicated road racer, which only made it to prototype stage) and similar to the RA41 & RD48. The RR 250 machines featured large alloy 2LS drum brakes and were also fitted with fairings from the YX18 as were Fuel tanks and seats. There was no provision for a rear guard (fender), but a front was available although not fitted for the Daytona race. Fuel tanks had flip up type filler cap and there was no provision for a fuel tap; this was fitted inline between the tank and the float chambers.
Engines were YX24 spec Asama racer units based on the 5-speed YDS1 engine. The cylinders were now alloy construction gaining a weight saving over the older YDS1 Clubman Racer engine but pistons still retained 2 rings at this point. Ignition was by Hitachi MC-2RY magneto and carburation was provided by 2 x Mikuni-Amal 276 27mm carburettors mounted on long alloy inlet manifolds with float chambers bolted the rear of the engine via anti-vibration mountings.
Fumio Ito lead the team with Yoshikazu Sunako in support, both veterans from Asama and both would make up part of Yamaha's team in the 1961 World Championship Grand Prix. It was of course Ito's 2nd trip to the US after leading the team at Catalina in '58. Both riders were overwhelmed by the size of the track at Daytona when they arrived.
Ito rode the #3 machine and Sunako #4. They finished a very creditable 5th & 8th places in Yamaha's 1st official road race debut on US soil.
Yamaha's website states that the special RR machines (with RD48 frames fitted with YDS1 Asama engines) were not the 1st choice for the Daytona race as Yamaha were hoping to run the new RD48 disk valve machines, ahead of the World Championship races soon after Daytona, but these were not ready in time. Instead these unique prototype machines were built and used. But it makes far more sense to think this was entirely a commercial decision to promote the upcoming production racer, which was soon to follow on, taking over from the YDS1 Clubmans Racer.
US Yamaha development riders and works supported riders such as Tony Murphy and Dave Buising were given rides on the machines in private testing sessions and the bikes received much praise over the previous YDS1 Clubman racer.
"I had a chance to try out the specials that the factory had down at the International at Daytona" wrote Dave Buising to fellow YDS1 Racer Geoff Kellond, "They had beautiful brakes, double leading shoe front and rear, and were very light. Weighed 192 lbs with fairing." he went on.
The Daytona machines were essentially works prototypes ahead of the official very limited production RR 250 model which were marketed in very limited numbers; 10 across the entire US, soon after the event.
Although no colour photos have been found to date, witnesses verbally described the colour scheme of the bikes as "black tanks, with red fairings and seat unit, with Production Racer written on the back of the seat unit". It is also able to see that the frames were not black, but a lighter colour, such as grey and the front fork sliders were white or perhaps yellow- as can be seen in the above photo.
The "Yellow Tankers" or "Yellow Road Racers" as they became known received an improved, slightly stronger frame than that of the works machines, which had an additional length of tubing welded over the top of front downtubes and onto the headstock, a feature which was to stay on the frames from the Yellow Tanker right through to the end of the TD1 range.
A Yamaha advert in UK magazine from October 1961, showing the Daytona RR racer (Sunako).
Works RR 250 Found !!
2021 saw the discovery of a frame (and wheels) believed to be that of one of these 2 important machines raced at Daytona. For many years it had been thought to have been sent back to Japan, destroyed and lost over time, although there were rumours the bikes remained in the US.
When compared to a regular Yellow Tanker RR 250 frame below (The chrome plated frame behind ), it is clear to see that there are many subtle differences. Note: this RR 250 frame (the black one below) has had some later work and alterations, such as the TD1A-C type tubular footrest hangers added, a common update as the early plate type hangers were the first things to bend and get damaged in a crash, plus a TD1A-C steering damper bracket was also a later addition.
The most significant difference is that there is no additional reinforcing tube welded over the tops of the front downtube at the headstock, in fact it may well be the damage sustained on this actual bike that may be responsible for this later addition as this frame had suffered a bend at this actual point and had subsequently been straightened and repaired. It can be seen that the tank mounting tubes on the headstock gusset plates have been trimmed away to get at the headstock, as a reinforcing tube was welded between the headstock and rear downtubes - a mod often seen carried out on the TD1 range to try an improve handling.
The position of the front fairing/tacho bracket is also an obvious difference but there are also more subtle differences... which are not easy to notice unless side by side, such as the construction techniques and the fact that there is no frame number stamped on the headstock where the Yellow Tankers numbers are.
Above: Traces of original grey paint (a similar colour to the YD-A) can clearly be seen on the steering stop bar on the headstock, confirming that this frame is indeed one of the Daytona works machines.
Coincidentally and quite fortunately, I already have an original works Asama YDS1 engine to fit one of these machines, which features 25% lighter magnesium crankcases and is fitted with hand finished knife edge conrods modified almost identically to the YD-A.
As opposed to the standard YDS1 engine number the magnesium engine has a D6 engine number, as per the RR Yellow Tankers, although with a much early number and with a sideways 1 used for the dash. Very much in keeping with the one-off numberings seen on later works machines. The D6 prefix would of course, confusingly become the prefix for the standard YDS2 and TD1 range of engines.
So, hopefully we should be able to bring back one of these very significant machines in Yamaha's history back to life.
If anybody has any pictures of the Yamaha's at Daytona in 1961 I would VERY much like to see them please.
Above, showing the weight difference between the magnesium crankcase compared to a standard YDS1 alloy case. After several failed attempts, it was found that the magnesium required aircraft grade zinc chromate to preserve them after they were vapour blasted.
The gearbox in this engine is interesting too, as it features the later ratios and improved selector forks, which were carried through to the YDS2, showing that this was a clearly a later YDS1 based engine and/or a prototype
The frame was blasted to remove the paint and inspect for any stampings and other damage etc. No number stampings at all were found. Fortunately, there was no other unexpected damage.
The unusual cutaway and holes for a gear lever change over devise is clearly seen on this frame, that i had thought was a later addition surprised me. The cutaway was cut at the same time as the swinging arm plate itself as the same machining/cutting marks show, as the cutting marks are the same along the whole profile..
Above: After blasting the frame, there is no trace of any numbers stamped or stamped and erased, anywhere on the frame.
Below: The unusual cutaway and holes for a gear lever change over devise is clearly seen on this frame, and the cutaway was cut at the same time as the swinging arm plate itself as the same machining/cutting marks show.