The First Wheeled Hummer (And My Only One): Harley Davidson’s Little (DKW) Two-Stroke

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– Posted on August 24, 2020

(first posted 10/19/2011)    This is what happens when you fail to stay on task: I was researching the transition of DKW to Audi, and got distracted with the fact that DKW was the world’s largest motorcycle manufacturer in the twenties and thirties. And that DKW’s brilliant RT 125 from the thirties was so advanced, that the Allies all made a grab for it, either the whole tooling (Russia) or at least the blueprints (England, US, India). And no less than Harley Davidson used those blueprints to build their little two-stroke Hummers. And then the light went on: I used to ride one of those! Time for a little more digging, and sharing.

DKW was of course the Mother Lode of two-strokes. Their very advanced fwd cars inspired the Saab and a raft of other imitators, and they continued until way too long, until the mid-sixties F102, which became the Audi when it got a four stroke motor. Let’s take that up another time. Meanwhile their radical RT 125 bike arrived in the thirties, and set the world on its ear. It was by far the most advanced light bike, and would become the most copied motorcycle ever. Why?

The two stroke engine had been around for some time, but it was typically a lazy and low-rpm, low output affair. Its most popular use was with marine engines, because the lack of moving parts made them more reliable. But the crude cross-flow porting meant inefficiency, and poor performance at higher revolutions.

In 1926, Adolf Schnürle went to work on the problem, and devised a system of ports that that created effective scavenging, essential to good combustion, especially at higher rpm. The modern two stroke was born, and Schnürle porting, along with other variations on the theme, made it possible (and wiki made these nice animated graphics possible). The DKW RT 125 was the first bike to take full advantage of it. Finally, a small displacement bike could offer decent performance. A fact not overlooked by the Allies.

The Russians took the tooling and built versions of it for decades. The Polish WFM was built until 1985! The British turned it into the popular BSA Bantam. And the Japanese copied it, and it became the first modern Yamaha (above), the progenitor of that long line of two-stroke bikes.

And in the US, Harley Davidson made good use of the blue-prints, and tooled up to produce a line of light bikes that started in 1948, and finally petered out in 1966, having been crushed by the (then) more modern Japanese bikes.

They weren’t technically called Hummers from the beginning, like this first year 1948 Model 125.  And with all of 3.5 hp and a three speed transmission, the top speed was some 45 mph. But the power levels went up, a fourth gear was added, and in the fifties, this was the way to get started on a small bike. “Perfect for the paperboy”.

The HD 125 was promoted for its economical transport qualities. Eventually, that created a rut for them, as the Japanese bikes had a much more fun-loving image.

Anyway, I had owned a Bridgestone 90, a typical small Japanese/Yamaha style bike for a while. As I was on the go perpetually, it quickly went by the wayside. But the following summer, I shared a house with some guys, and one of them had a green little bike laying in the backyard that he couldn’t get started. He’d brought it from home, where he found it in a barn.

I’m not sure exactly what I did to get it running, probably a new spark plug. But I then appropriated it for myself. I’m not totally sure what vintage it was, but I seem to remember it only having three gears, and being decidedly pokier than my smaller Bridgestone 90, which could hit sixty mph. But it was perfect for putting around Iowa City in the warm summer, and it fit tall me much better than the narrow-bar Bridgestone. The little Hummer had that typical HD riding position that was intrinsically more relaxed. And it was a bigger-framed bike than the small Japanese bikes.

The only downside was that the Hummer was a one-person affair. Look, but don’t ride. My Bridgestone, small as it was, always had room for a passenger. Even if my knees were hitting the handlebars.

Maybe this is the real reason why Honda and the other Japanese cornered the market.

The actual name Hummer was adopted in 1955, for a stripped-down economy special. The name came from Dean Hummer, a HD employee or dealer, who suggested it as a way to fend off the growing Japanese competition.

Not that it did much good. Even though the Hummer grew to 165 cc, and a whopping ten horsepower, Harley Davidson was unable to make it work, given that US wages were so much higher then. And the competition was constantly upgrading and improving, which was making the Hummer look more like the thirties design it really was. This 1962 Pacer was obviously trying to evoke the big Harleys.

And the very last of the series, the 1966 Bobcat had a stylish fiberglass one-piece “body kit” to make it look current. But by then America was awash in Hondas, Suzukis and Yamahas. HD ditched the little Hummer, and never looked back. Its future lay elsewhere.

(Pictures and facts courtesy harleyhummer.com)