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The Zundapp KS601, Continued

  
Around 1949, Zundapp began preliminary design work on an entirely new model for the KS series. This motorcycle was updated with plunger rear suspension - a major improvement over none - and telescopic forks to replace the traditional Zundapp parallel four link fork found on its predecessors.

Early efforts involved a small displacement engine but Zundapp engineers began playing around with installing the wartime KS 600 motor in the frame. Ernst Schmidt, chief designer, liked the idea. In late 1949 the first prototype emerged, painted black, with a beefed up chassis to handle the larger motor.

The Zundapp KS601 Arrives on the Scene

In early 1950 a second prototype was completed. With an engine that differed from the original KS600 in many respects the bike was christened the KS601. To further distinguish it, not only from BMW but also prior Zundapps, the black frame now sported fenders, tool box, fuel tank, fork cover, and head light housing all appointed in the famous Zundapp lime green.

The newly designed 597 cc motor, with two Bing carburetors, produced 28 Hp at 4700 Rpm with peak torque of 33.6 Ft. Lbs at 4000 Rpm. This was notable power, more than the Volkswagens of the time, and made the Zundapp KS601 an immediate hit with enthusiasts. The motorcycle's unique appearance and its new engine earned it the well known title of "Green Elephant".

As with the production bikes, the telescopic forks of the new chassis had almost 5" of travel but furnished no dampening. A shock absorber mounted on the triple clamps between the fork tubes and bearing on the heavy front fender directly above a strong brace provided compression dampening. In the rear, the plunger type suspension had about 2.5" of undampened travel and was carried into production unchanged, the only exception being the axle trailing the shock housings rather than leading as on the prototype.

Power was transmitted from the engine via a two disc dry clutch in a heavy flywheel driving the peculiar but extremely smooth shifting and reliable duplex chain drive transmission, shown in the sectional view on the previous page. From the transmission a drive shaft with two kardan U-joints delivered power to the spiral bevel ring and pinion final drive which drove the rear wheel via a splined axle that engaged the hub. I have seen final drives with both straight and tapered splines, both clearly designed for use in the KS601 because there were provisions
Click for a larger sectional view of the Zündapp KS601 Engine
Sectional View of Zundapp KS601 Engine and Components.
Click image for larger view of the Zundapp KS601 engine.
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Right-hand Cylinder Head
Sparkplug with Cap
Pushrod
Right-hand Cylinder
Mushroom Tappet
Tappet Guide
Camshaft
Ignition Coil
Camshaft Gear
Breather
Voltage regulator with
Reserve Current Cutout
Valve Adjusting Screw
Rocker Arm
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Valve Spring
Valve
Compression Rings
Piston Pin
Piston
Connecting Rod
Oil Sump
Oil Filter
Crankshaft
Crankshaft Gear
Oil Pump
Armature
Generator
Contact Breaker
for the plunger suspension in the castings. I asked James Marshall, aka the Zundapp Fool, why the two versions. He explained the tapered or "cone" version was used on the 1951 and '52 models. In 1953, the factory began producing the straight or "barrel" spline, presumably because it was cheaper to manufacture. Interestingly, both the front and rear Zundapp KS601 wheels have the final drive spline in the hub so they can be used interchangeably, which allows tire rotation to evenly distribute wear, but one needs to remember the two types of spline if purchasing another wheel.

The first production KS601 left the factory in the summer of 1951 after extensive and successful testing of the prototype versions. This newest Zundapp received enthusiastic reviews from the various motoring magazines of the time. It proved to be popular not only with the motor sports crowd, but also with average owners who quickly came to appreciate its rugged dependability.

In 1954, a father and son team rode a Zundapp KS601 on a highly publicized 20,000 mile trip around the world, after which the bike was dismantled by a group of motorcycle journalists and factory technicians. They reported the machine showed surprisingly little wear after the incredibly abusive journey, and were awed by its durability in conditions they felt would have destroyed many of the bikes offered by Zundapp's competitors.

Despite such positive attention from the press, sales of the Zundapp KS601 were lagging considerably behind similar models from BMW. The factory adopted a number of strategies in the attempt to boost interest, including introduction of the KS601 Sport with 34 horse instead of the standard 28. They offered a number of additional color choices and targeted the United States in a campaign to get a toe hold in that growing market. All to no avail. Part of the issue was Zundapps being widely viewed as heavy duty sidecar machines. Despite handling that was superior even to BMW's they just couldn't shake that reputation with the solo riders. Also, the world economy was picking up and more people could afford to purchase cars, which had obvious and attractive advantages over motorcycles for practical day to day transportation.

In a final attempt to bolster sales the Zundapp KS601 Elastic was introduced in 1957, featuring the Sport engine and a new swing arm rear suspension. Aimed exclusively at the US market, this fine motorcycle was too little too late. Production of the KS601 in all its flavors from 1955 to 1958 failed to reach 1000 motorcycles. Total production across all the years of its manufacturer just barely topped 5000. In 1958, Zundapp sold the Nuremberg factory to Bosch and production of the Zundapp KS601 ceased.

Even those few Green Elephants were able to impress an admiring public with their remarkable ruggedness and reliability. Devoted Zundapp KS601 owners formed organizations all over Europe. One such group began an annual winter ride in 1956, the Elefantentreffen, which grew at one point to tens of thousands of participants. The meet survives to this day - despite having experienced some tribulations - and still boasts a couple thousand attendees, but necessarily few on KS601's.

As the years passed parts became more difficult to obtain inspiring numerous approaches to keep the venerable KS601 going. These included clubs organized to purchase large lots of spares and forays into modification of parts from other vehicles to be used in the Zundapp. Now, thanks to the KS601's well earned and enduring popularity, aftermarket parts sources are cropping up all over Europe. Unfortunately, those few outlets which once existed in North America have pretty much vanished.

In 1984, the Zundapp marque and all the equipment was sold to a firm from Tianjin China which primarily built smaller displacement bikes for a country that views motorcycles as basic transportation. They also produced the WWII era KS500 which was apparently of quite high quality and true to the original, opening a new parts supply for the gleeful owners of those models but not, alas, the KS601.

In 1999, a German firm purchased the Zundapp name. The new owners are known to have substantial knowledge and interest regarding the KS750 but it is not yet clear what their intentions might be. While I've been unable to find any reference to current activity, it's encouraging that the marque is once again German owned. Who knows? Maybe we'll be able to buy our spare parts from Zundapp itself once again.

  
Last updated 02-17-18
Email:  mechanique at wmol dot com

Zündapp drive shaft, U-joints, and pinions.