https://youtu.be/H77YPGESSKU
My first motorcycle was version four years later, the bigger version, a YAS1 125cc twin, 1971. I could get 70mph, chin on the headlamp nacelle, slight downhill. Wonderful. Red and chrome. I think it had five gears. Extremely willing motor. I looked like a circus bear on it at 6’ 3”.
What a sophisticated piece of mechanical engineering, for its era.
Yamaha & Suzuki owed their early prowess in two strokes to two East German men, one a bike racing champion and the other a two stroke engineer. They defected to Japan and the rest is history. There have been a lot of clever German engineers! Is there an engine they didn’t pioneer?
Best wishes
Mike
Ps: I’m blanking on the names, but perhaps one was Ernst Degner? The defection story of whichever was the racer is absolutely incredible. In short, his minders lost focus because “they knew” he’d not run away that weekend in Scandinavia, because he only needed a couple of points & he’d been crowned international champion of that class. Unknown to his minders, he and his wife had decided to use that very opportunity because nobody would except him to give up his one chance to be world champion. I recall they both made it out & it turned out that her defection was by far the riskiest.
Though I owe my lifelong love of two stroke multicylinder machines to these people and I honour them often in the back of my mind, I have a vague recollection that things didn’t work out well for them personally and both perished young, far from home.
It wasn’t limited to expansion chamber theory and practise, but also exact piston port timing and reflection of exhaust pulses, stuffing the next fuel / air charge back into the open cylinder port just in time for the rising piston to seal it off again for the next power stroke. There was another fellow, I vaguely recall as Herr Schneurle, who invented a particular way of designing aspects of the top end of two stroke engines which greatly increased their power. Another German, obv 🤭
As for the several generations (no joke) of clever engineers who focused on creating fuel / air mixture ratios and the optimum amount of each charge, the art of carburettors was perfected through an unexpectedly large number of variations, both theoretical and dead reckoning. By the late 1970s, they were so good at accurately metering fuel, air and sometimes total loss oil lubrication that as they began to be phased out in favour of fuel injection, the latter was much worse initially than the technology they were usurping. Carburettors are, however, spookily difficult to get spot on.
I won’t attempt to explain it, but there really are at least four distinct fuel / air metering systems all integrated inside that innocent, oddly shaped soft alloy casting. Over time, you can diagnose which “circuit” in which cylinder is misbehaving and adversely affecting “fuelling feel”, which is intolerable to folk like me. Yes, I could “ride around” the problem. But I want the issue confirmed and resolved. I still recall vividly the first warm, sunny afternoon when I took out my oldest bike, a 1977 Suzuki GT380B two stroke triple, on which I’d been “tinkering” on and off about a year, since pulling it out of long terms storage of over 20 years. Initially it was seemingly impossible to even get it to run at all, let alone to ride the thing. That perfect ride confirmed that, at last, I had everything spot on with all three carburettors (everything else was operationally alright, though the bike looked extremely tatty). I took it around minor A roads in rural East Kent and it drove off the throttle so beautifully that I remember shouting with joy as I exited a band and held it near wide open throttle, through the gears, and everything was in perfect harmony. I couldn’t stop grinning spontaneously all evening. Bunny asked me why I was so happy so I told her. She raised an eyebrow and declared that I was very odd and she loved me anyway.
Best wishes
Mike
👉
https://t.me/DrMikeYeadon