The first of the real giant killers
Introduced in 1968, the Yamaha YAS1 defies all motorcycle logic, even by today’s standards of miniaturization. As a development of the previous Yamaha roadster twin designs, the vertically split, twin-cylinder engine is compact and powerful, this in turn is wrapped in an equally diminutive frame that does its best to hold the wheels inline and weighs next to nothing in the bargain. Once on the move and buzzing away in its sharp power band however, the truth emerges, the 125cc two-stroke is more than a match for machinery several times the capacity. The main differences between the AS1 and the AS1-C are the high exhaust pipes, slightly raised front fender, the braced handlebar, and that the forks are covered with boots instead of the metal covers.
For the day, the AS1 featured some advanced design work, worm ports for example, Yamaha’s way of describing the way the transfers meander their way up the side of the barrel, fed the domed compression chambers before the gasses escaped into semi expansion chamber type, chrome exhausts. This returned an impressive level of performance that when compared to the established 125cc machines of the day went more like a 250cc one.
For such a small machine and engine, the AS1 is incredibly tough, able to handle most tasks with comparative ease and with few failings. Even the dreaded top end seize would be few and far between thanks to the efficient Yamaha auto lube system that, providing it is maintained and kept supplied with oil will look after the reciprocating parts nicely.
Yamaha did produce a full race kit for this and the AS3 engine, enabling it to be turned into a very effective race machine. So effective that examples of them, albeit very highly developed and by then water cooled, actually won two world titles in 1973/74 ridden and largely created by of the late Kent Andersson. This makes the tiny 125 Yamaha the only road based machine to actually take a world title, let alone win a GP.
Unfortunately we didn't get around to taking any photos before we started tearing this puppy down, but it is a mostly complete bike and doesn't appear to have any major issues. She will be getting a fresh engine rebuild, carb overhaul, fresh paint, fresh tires and rubber throughout. We don't want to stray too far from stock on this one.
**Update Aug 30th 2014**
Got everything back from the powder coater yesterday. Once we get the parts back from the vapor blasters we can paint the tank and other bits and start to reassemble!
** Update Sep 19th 2014**
Wheels are polished and trued, new bearings pressed in
**Update Oct 14th 2014**
The tank, side covers, and oil tank have been painted. The motor has been reassembled and seated in the frame. Wiring is completed and ignition timing has been set.
**Update Nov 7th 2014**
**Update Nov 11th 2014**
Almost complete, installed the exhausts, fresh brake pads, installed and routed all the cables. We are still waiting on a few bits before the first start.
**Update Nov 30th**
Initial start was a success, we will need to adjust the carbs but will be finishing her up soon and posting final photos!
CLICK HERE TO SEE THE FINAL PRODUCT!