ORIENTAL ANGLES
How far back does oil injection go when it comes to Japanese two-strokes? That the
Scott twins had some form of two-stroke oil (or 2T) pump is a given, yet it was those impertinent upstarts at Yamaha who first honed and refined the various systems that had appeared on the Saltaire twins in the mid1920s.
In the intervening years (almost four decades), few or any two-strokes had anything significantly better than a 32:1 premix; in fact, given the oils of the day, 20:1 was the norm.
One part oil to 20 parts petrol doesn’t sound excessive until you figure out that’s actually 5% lube – i.e., a heck of a lot of smoke.
Several companies tried but failed to devise a genuine variable oil metering device for the humble stroker. However, there seemed to be very little commercial drive given that twostrokes were essentially commuter fodder and, thereby according to the perceived wisdom of the day, really not worth the effort, apparently!
The status quo changed when a supposedly inconsequential East German manufacturer started winning GPs on small screaming twostrokes. MZ led the way and the Japanese factories (with the exception of Honda) followed.
By 1961 Yamaha and Suzuki were going large on smaller capacity machines at racetracks around the world, with Kawasaki soon to do the same. Many (or most) Oriental 2T race bikes were seizure-prone and Yamaha was adamant that there had to be some practical and reliable interventional measure that would save both its riders’ lives and their bikes’ engines. By June 1961 its collaborative work with carburettor maker Mikuni was debuted at the French GP. Variable ratio oil injection had finally arrived!
Based on its track experiences, the Iwata factory progressed to fitting oil injection – or Auto Lube, as it named it – to two key models. The YG-1D 80 and YA6 125 were showcased to the public at the 1963 All Japanese Tokyo Motor Show and certainly raised a few eyebrows.
Yamaha as a motorcycle manufacturer was only eight years old at the time, yet here it was taking on all comers with a revolutionary design proven at GP level. Such was the impact of the concept and design that the American Society of Automobile Engineers awarded Yamaha a commendation and the USA’s Auto & Motor Sport magazine gave Yamaha’s Auto Lube an excellence award for Safety Features and Engineering Advancement. The rest of world simply offered up profound thanks that there was finally an alternative to carrying around a small grubby bottle of oil!
The Japanese motorcycle industry was a very competitive place in the early 1960s and it wasn’t very long at all before the rival marques also adopted oil injection systems of similar design – but with one key difference. Yamaha had the wit and guile to patent its particular system, and importantly, its locations. Even though Mikuni would supply 2T pumps to the likes of Bridgestone Kawasaki, Suzuki and latterly Honda, only Yamaha’s system was fitted in line with the crankshaft driven off a helical spur gear. Even more cunning was the use of integral check valves within the pump bodies. Using a simple coil spring and ball bearing, the Yamaha system precluded the oil tank from emptying out under gravity into the crankcase. Yamaha’s patent covered both aspects rather neatly, leaving the other players to fit check valves in the oil lines upstream of the pump.
The Autolube system proved to be unnervingly reliable and its only critics were those who felt the inexorable desire to fiddle with it without the relevant skills. Only they and those who suffered from their incompetent tinkerings have ever had an issue with one of Yamaha’s rather fine pumps. Even if the firm has effectively distanced itself from stinkwheels you can still buy service kits from www.ydsparts.com among others. Fed decent 2T, these clever pieces of Japanese miniaturisation still help to put smiles on rider’s faces some 60 years after they were first introduced.