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 RR250.
Initially, the works machines were produced with frames almost identical to its disk valve predecessors, 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 RD48. The RR250 machines featured large alloy 2LS drum brakes and were also fitted with fairings from the YX18. There was no provision for a rear guard (fender), but a front was available although not fitted for the Daytona race.
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 to at Catalina. Both riders were overwhelmed by the size of the track at Daytona whe 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.
The special RR250 machines 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 prototype machines were to be used as demonstrators for the forthcoming production racers, which were soon to follow on 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 RR250 model which were marketed in very limited numbers, 10 across the entire US, soon after the event.
The production batch of Yellow Tankers 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.
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 (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 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.
The biggest 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.
The position of the front fairing/tacho bracket is also an obivous 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.
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.
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 ratio's 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.