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The unique identity of this YD-A Asama Racer

It occurred to me that I have not provided evidence which highlight this bikes identity in one concise post, so here are the facts which can be proven to date. For the record, this is simply stating facts that can be supported by evidence nothing more, nothing less.

1) Yamaha sent across 1 machine to the USA on which arrived on 4th Feb '58 as a prototype for secret testing and development ahead of the other 4 which which were shipped on 4th March landing on April 7th.

2) On their website, Yamaha quote "Yamaha sent five motorcycles to compete in the 250 cc class. In addition to a modified YD1, which had swept to victory in the second Asama Highlands Race, the company modified four other machines for riding on uneven surfaces..." This of course maybe PR spin, that they sent the Asama winning YD-A.... but there were only very few YD-A's to send...

3) This machine, YD-A frame # YD21 / Eng # P51 can be proven to be the 1st machine ( out of the 5) sent across, which according to the Yamaha website above, would make this machine (if the website is true) the Asama winning YD-A machine as ridden by Osamu Masuko. The following points make the machine identifible:

4) The frame has no provision for 3 point mounted footpegs - no large welded mounting spools as fittted on the other 4 machines.

4a) Period photo's show the machine with single mount footpegs, which were welded to the top of the lower frame tubes, in slightly further forward position, which this bike has evidence of (see below).

5) The engine (54 x 54 # P51) had a "O" painted on the inside of the crankcase which correlates with the "O" on the outer crankcase clutch cover which can be clearly seen on contemporary photo's of Masuko riding at Asama, Fumio Ito's YD-A Did not carry this marking at Asama.

6) This frame has YD-A stamped on the headstock. The other known machines do not have this stamping, why this difference between frame stamping is not known yet but it does make this frame "different" to the others.

7) The Catalina Prototype was pictured at Sonny Angels shop (see below) and Sonny's race notes record engine P51 being used in many races.

8) Other photos of Sonny's bikes show 1 x YD fitted with a conventional fairing. YD21/P51 had a mount welded on for a conventional fairing.

Above: "O" painted on the clutch cover on Masuko's YD-A at Asama.

Below: "O" painted on in inner crankcase of P51.

And in contrast with Osamu Masuko's "O" on #75 there is no such "O" painted on Fumio Ito's YD-A #60 as pictured here on the Mount Asama start line, making the case much stronger that the above machine was indeed #75.

Below: Sonny Angel with Gene Wise's works YD. Note the redundant 2 large footpeg mount on the bottom of the frame tube. There are no signs of these on YD21/P51.

Above Catalina spec machine - 1 of the 4 machines which followed the original YD-A - note large footpeg mountings.

Below. The bottom of the frame tubes of YD21 - There are no signs of any weld scars.

Below. But, there is a single weld scar on the top of the lower frame tube

Below. Which correlates with this machine. Picture taken at Sonny Angels workshop - P51 is recorded in his race notes alongside PQ47.

Below: And also correlates with the pictures of the Catalina Prototype

What can be said for certain, is that this machine is a 1957 YD-A Asama Racer, plus it was the Catalina Prototype which raced in the '58 Catalina GP and was one of the 2 x YD's that Sonny Angel / Cal Rayborn later campaigned.


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