Zundapp K 800 team

Zundapp K 800 team

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Anyone who drives a sidecar all their life and constantly dreams of Zundapp has earned it: a K 800 with a four-cylinder boxer and a mighty, stylish sidecar.

There was no doubt at all: the ideal vehicle for Gerd Windhorst could only Zundapp are called. To warm up, well, he had an AWO, then a Max team. But when the money was enough, a KS 601 Sport with a Steib TR 500 came into the house. This team still exists, not a single day canceled for over 40 years. “And in that”, the 74-year-old master blacksmith smiles, “we raised our children.” When that was done and there was time for our own wishes again, a KS 750 was added around 1980 and the K 800 a few years later. Coronation and memory at the same time: "My father always raved about it."

Zundapp K 800 team

Maximum solution

Performance characteristics and design options

Only the entry-level models called Derby still had a conventional tubular frame. Above this was the K 200, also with the tried and tested single-cylinder two-stroke engine, but – and therefore the K – with a cardan drive and double-loop rigid frame made of box sections. This was followed by the models with completely redesigned side valve two-cylinder boxer engines with 400 and 500 cc. Finally, the crowning glory was the 600 or 800 cm³ four-cylinder boxer, which should be understood less as a provocation towards BMW, but as an attempt to civilize the motorcycle as much as possible. Especially in the upper class and beyond sporting use, the single-cylinder had outlived itself; with their large luxury tourers, the Americans showed a path to which some English brands opened up and which attracted Richard Kuchen’s very special interest: a four-cylinder boxer promised, always as Side valve, a silky smooth run with extremely delicate use of power from the speeds and at the same time lowest sustained power.

Maximum performance didn’t count so much for kitchens, then he could simply have drawn an ohv motor. No, the performance characteristics and the design possibilities of the side valve inspired him. The two gray cast iron cylinders on each side have a flat, light metal cylinder head; the two inlet valves on the inside are supplied by a common intake port. This leads inside the engine housing to the single carburetor mounted above the gearbox, and if you have a little imagination, you can start calculating the intake paths. The design of the cooling fins and even more the characteristic air baffle on the rear cylinder make it clear that its heat balance was seen as a problem. More on that later. The power is transferred via a multi-disc clutch to the chain transmission, which is typical for kitchens and has been implemented for the first time in the K series, and the rear wheel is then driven by a shaft. It has no damping elements, which is why the higher elasticity of the kitchen gearbox compared to a gear construction was very welcome. The ball gears come from the automotive industry, their long gearshifts are less noticeable in a trailer operation than in a brisk solo drive.


The chains of the kitchen gear are clearly elongating. But they guarantee elasticity – and you can change them.

Things get complicated under the front cover of the engine housing, which is kept very smooth: the crankshaft drives the vertical shaft of the ignition distributor, which also comes from car stocks, via a worm gear. It sets the camshaft in motion via a chain, which in turn uses spur gears to get the generator going. Also by means of spur gears, the crankshaft drives the oil pump that works in the oil sump, which, by the way, circulates three liters of lubricant. Behind the – elegantly covered – alternator sits the – of course also covered – carburetor, and there are two stories about it: The part installed at the beginning made the K 800 a top-class drunk, because the negative pressure of the suction cylinder is initially distributed calmly via the meter-long intake system of the four-cylinder. The gas tap had to stay open forever so that the mixture could get into the combustion chambers and finally propulsion began. Then it’s better to buy an extra sip in the acceleration phase and quickly turn the tap back to half-throttle. That is why the K 800 quickly got an Amal carburetor with an accelerator pump, and consumption leveled off at around six liters.

The other story? Comes from Gerd Windhorst. It drives around without the carburetor fairing, and for good reason. Under certain conditions the generator and engine can build up a lot of heat under the whole lid. And then sometimes a happily evaporating droplet of petrol and a tiny spark on the lima coals are enough to set the whole beautiful Zundapp on fire. So it happened and noticed just in time during a family outing with several teams. They take place regularly at Windhorst – true to the old slogan: "With Zundapp around the world, saves work, time and money" – and the K 800 does a good job. The proud owner is by no means afraid of rallies with daily stages of 200 kilometers, he has already covered a total of 30,000, mostly accompanied by his wife.

Ideally suited for the heavy team

And that’s how it was intended when he bought the K 800, built in 1936, just around the corner. Still looked pretty good, but the engine was "on", as they say in northern Germany. So Gerd Windhorst did it and discovered that a bearing seat for the crankshaft was not aligned with the corresponding roller bearing. It had been milled wrong; sensitive thing. Since then he has renewed the bearings, and they will be back soon. He thinks the kitchen gears are great, looked in at the time, found no significant wear and everything has been reinstalled. Later, the passionate Zundapp collector and restorer found the appropriate yard goods and has since exchanged the chains on some gearboxes. 

“At some point,” he remarks in a relaxed manner, “the K 800 will probably get it.” Windhorst mentions the rear cylinders as the only weak points, but because he had the bore two hundredths larger, there is calm. No piston pinching, nothing at all, and he doesn’t know anything about oily candles either. Instead, the engine runs extremely smoothly, and is ideally suited for the heavy team despite not exactly lush flywheels.

Imposing record-breaking sidecar

One thing was clear from the start: the K 800 should not be left alone. At her side is the truly impressive record-breaking sidecar from the production of the Viennese Franz Castek. Windhorst found it, it is hard to believe, two or three villages further, in the middle of the north German lowlands. With the chrome-plated, arm-thick tube of its arched chassis, which is open at the back, the record is a real eye-catcher, especially in the expansive touring variant. On each side, the seamlessly drawn pipe bend carries a leaf spring on which the boat made of sheet metal rests. However, it is only fixed at the front end of the spring, on the rear end it has a spring roller glider legally protected for Franz Castek. The master mechanic advertised it with flowery words: "These gliders try to compensate for the smallest as well as the strongest impact rolling on the long spring, so that the body always floats smoothly and gently." As Castek promises, "driving is possible even on the worst roads". Gerd Windhorst can only confirm that: he "doesn’t actually know anything" about complaints from the sidecar.

Deliveries were made in all possible decors, and the boat restored by Windhorst also has a lively design. Of the extras offered at the time, it features the sidecar brake and convertible roof, not to mention the streamlined side lamp and certainly not the decorative figure on the boat’s nose. It has the shape of a hovering guardian angel, and it does its job – now even as a fire fighter – really well. That calms Gerd Windhorst immensely, because his joy in this team is unmistakable: he gives the cold engine three or four little gasoline injectors with the throttle grip, turns on the ignition, steps on the kick starter twice, then he smiles happily. The Zundapp waited in steadfast and calm idling until Windhorst had adjusted his glasses, then he shifted into second gear – “I only need the first one in the mountains” – and drove out of the yard. He has a fourth in it just over 40 – "But it also goes down to 30" – and then at the latest he knows completely again: "Such an elastic motor, it is probably unique."

Technical data of the Zundapp team


Air-cooled four-cylinder, four-stroke sv boxer engine, a camshaft below, two valves per cylinder, actuated via a tappet
Bore x stroke: 62 x 66.6 mm
Compression: 5.8: 1
Displacement: 791 cm³
Power: 22 hp at 4300 rpm

Power transmission: 

Multi-disc clutch, four-speed duplex chain transmission, shaft drive

Landing gear: 

Double loop frame made of pressed steel profiles, trapezoidal fork made of pressed steel profiles with hydraulic damper, wire-spoke wheels with steel rims, interchangeable, tires 3.50-19 front and rear, simplex half-hub drum brakes front and rear


Record touring sidecar made by Franz Castek / Vienna, arched tubular steel chassis open at the rear, attached to the motorcycle frame with four connections, 1 ½-seater sheet steel boat, mounted on leaf springs, unsprung sidecar wheel, 3.50 x 19 tires, half-hub drum brake

Mass and weight: 

Wheelbase 1405 mm
Weight with a full tank 193 kg (trailer approx. 320 kg)
Tank capacity 12 l 

Top speed: 

approx. 125 km / h (as a team approx. 105 km / h)

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