Steve Cooper looks at a single year model that you can still pick up for not a lot of money.
That the Japanese motorcycle industry plagiarised the work of others is well documented. In the modern business world such artifice creates what’s known as a second-to-market product and often such offerings have some of the original design’s rougher edges knocked off them.
Yamaha had ‘borrowed’ the basic design of the pre-war DKW RT125 to produce its YA1 in 1955 and, just a few years later, cribbed Adler’s MB250 design to deliver the YDS1 sports twin in 1959. From there on the Iwata brand would refine, upgrade, hone and update the concept, but retain the original design featuring vertically split crankcases.
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From a technical perspective this setup made a lot of sense, supporting the main bearings snugly, thereby offering maximum rigidity. Unfortunately, such designs demanded specialist kit to pull the crank and cases together which, in turn, cost shop floor time and, by default, money.
By the mid-1960s Yamaha was already ‘on the case’ and designing a new horizontally split engine for its new 350. The ground up design of the YR1 350 Grand Prix delivered a class leading bike and the blueprint for a legion of other two-stroke twins. Oddly, Yamaha still, and perhaps perversely, retained the older, vertically split case engine design for its 250s despite the sales successes of the YR1 and the TR3 race bike derived from it.
The final iteration of the old quarter litre motor would appear in 1969 in the guise of the YDS6. This replaced the YDS5E – E for electric start – which many reckon wasn’t Yamaha’s finest hour and not in the mien as the previous YDS3s. For reference there never was a YDS4 due to superstitions about the number in Japanese folklore. Yamaha’s YDS6 (more often just called DS6) may have been restrained in appearance but it was still delivered the goods. A five-port cylinder was used to boost power for lighter, more agile performance, and the bike came with a hugely effective twin leading shoe front brake that bested those fitted to many of the that of its rivals. Strangely, and unique to the YDS6, was a pair of cigar-shaped exhausts sporting tulip-shaped outlets; nothing else in Yamaha’s catalogue before or since has featured silencers quite like those of the DS6.
Performance wise, the new model kept the zing and vava-voom of the old YDS3 motor; yet, at the same time, Yamaha had managed to increase flexibility. Having ridden both, I’d have to say the final version of a motor that could trace its origins back to the 1952 West Germany design is significantly easier to ride. By the time the DS6 arrived, Yamaha had honed its craft in terms of chassis technology and even if the bike didn’t quite handle like a British one it was much better than what had gone before. If Yamaha had set itself a target for the DS6 I’d argue it had aimed at Honda levels of all-round rideability with the added bonus of some Iwata pep and tuning.
Made for a single model year the bike effectively had a very short sales run in the UK and when news of its successor arrived sales swiftly petered out. Learners wanted the all-new YDS7 with its modern styling, exposed suspension, a tank without rubber knee pads and an overall look of the future, not the past.
Almost six decades after the DS6 broke cover it’s a rare machine, but not an especially valuable one. Even at the height of the post-pandemic classic bike frenzy a tidy DS6 wasn’t making more than £5000. Today you could buy a fully restored one (don’t waste your time on an example in boxes) for £7500 apparently, but you’d have to want a perfect minter really badly to be spending that much. Find an older restoration or a survivor and enjoy it for what it is and hope to pay around £2000-£3000. There’s a very good chance you may fall headlong for one of Yamaha’s hidden gems!
Original article appeared in Old Bike Mart. To subscribe, click here: https://www.classicmagazines.co.uk/old-bike-mart
