NSU Max double test – Kawasaki Estrella 250

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NSU Max / Kawasaki Estrella 250 double test

The max factor

From 40, a motorcycle needs special care. But when lubricating and anointing no longer helps, a facelift is needed. This is how the NSU Max became the Kawasaki Estrella 250: completely different – and yet completely the old one.

The finger presses the swab on the float chamber of the Bing carburetor until the fuel overflows: Then the key is pushed into the ignition lock in the headlight, the air flap of the carburetor is closed, the lever of the valve lifter is pulled, a tight man’s calf kicks the kickstarter with force – and the single cylinder releases a deep bubbling from the long silencer. "The right technology does it," laughs Herrmann Rapp, built in 1935, and is pleased that his self-restored NSU Spezialmax, built in 1956, starts up immediately, even in the severe cold at the beginning of February. The »special« stands for the second Max model series, which was built from 1954 to 1956: after the Max, which was sold from 1952, and before the Supermax, which was sold until 1963. Between 1959 and 1969, the industrial foreman owned a number of NSU maxes, which he used as solo machines, but also as a team draft horse and even as a racing machine for the now legendary "Zuvis" over a distance of up to 600 kilometers. Therefore he knows the single cylinder inside out.

NSU Max / Kawasaki Estrella 250 double test

The max factor

Kawasaki Estrella 250, which has been imported since 1994 (MOTORRAD, issue 10/1994) and underwent some technical changes for 1996, makes it easy for your driver. The choke on the carburetor greases the gasoline-air mixture. When the ignition key is turned – hidden under the tank on the left – an electric thermostat-controlled heater begins to warm up the carburetor. Then a push of the button and the motor pots little puffs into the ice-cold air.

The Max has a pressed steel frame, the Kawasaki Estrella a single-loop tubular steel frame. The surface parts of the Estrella are also made of sheet steel and the mudguards, headlight and taillight brackets are chrome-plated: luxury that hardly anyone could afford in the 1950s. The Max leads its front wheel in a pressed steel fork with a short swing arm and spring struts. The Estrella has a conventional telescopic fork. The Max rear wheel is cushioned by a modern-looking central spring strut, while that of the Estrella is cushioned by two "classic" struts – from now on, by the way, without a reservoir. NSU uses full-hub drum brakes, while Kawasaki relies on modern disc brakes. But the following applies: the chassis of the Estrella – apart from the disc brakes – has nothing that was not already there in 1956.

With 69 x 66 millimeters for bore and stroke, the Max engine corresponds to the short-stroke design of modern single-cylinder, while the Estrella engine with 66 x 73 millimeters is recognizable as a long-stroke. Valves operated by rocker arms and an overhead camshaft, which – a NSU specialty – is driven by two connecting rod-like push rods, do not suggest any veterans either. Block design for the motor and gearbox, the gear primary drive, a dry clutch and even a complex dry sump lubrication make the Max motor complete. That its valves are closed with hairpin valve springs and those of the Estrella with coil springs is almost a minor issue. The valves of the Estrella are also opened by an overhead camshaft, which is "only" driven by a roller chain.

And yet the Estrella has more to offer. More gears in the transmission – five instead of four. More watts from the alternator – 224 watts instead of 60. More compression – 9: 1 instead of a compression ratio of 7.4: 1. A balance shaft takes the vibrations out of the Estrella engine. Max, on the other hand: "She mercilessly vibrates everything down, "says Herrmann Rapp." At high speeds, handlebars and footrests hum like bumblebees. "Both machines were initially only delivered with swing saddles. The NSU with two saddles for the driver and pillion, the Kawasaki with only one for the driver: Up to 1995, its payload of 108 kilograms was too low for pillion use. Saddles have the disadvantage that you can hardly slide back and forth on them; The logical solution for Hermann Rapp was therefore a bench, as offered by NSU for the Max from 1956 at an additional cost. The industrial foreman built his himself, however.

For 1996, Kawasaki now also offers the Estrella with a bench. Above all, however, to make the Estrella fit for pillion without extensive changes to the rear of the vehicle. The bench is excellently padded and shaped and, pleasing for smaller drivers, at 740 millimeters, 30 millimeters lower than the individual seat. However, the saddle can still be retrofitted. Of course, 40 years have not passed by Max without a trace. But the difference is not as extreme as one might expect. The Estrella engine accepts gas more easily than the somewhat sensitive Max, thanks to its well-coordinated constant pressure carburetor.

The performance differs, however, as both get a nominal 17 hp out of 250 cubic centimeters – the Estrella at 7500 / min, the Max at only 6500 / min – insignificant. The Max is perhaps a little more handy than the Estrella; almost nervous. And even if the Kawasaki has more recent suspension, the NSU is still comfortable enough to keep up even on poor roads. In some parts of the Estrella, however, the progress can be clearly read. These are the quality of workmanship, the practical hand levers and switch units, their disc brakes – which are vastly superior to the Max full-hub drum brakes – and finally the smooth-running five-speed gearbox; In the days of NSU chief engineer Alber Roder, five gear ratios were used exclusively in the factory racing machine, the "Rennmax".

Compared to the Estrella, the four-speed Max transmission has to be shifted very carefully over long distances and also has a very long jump from third to fourth gear. And yet: The NSU Max remains the fame, was so modern 40 years ago to be that it doesn’t have to hide even today, and the Kawasaki Estrella, that it has come so close to the classic ideal of the 250cc four-stroke single-cylinder motorcycle, despite all its modernity, that a comparative sideways glance makes sense. Or, as the former head of the NSU advertising department, Klaus Westrup, as the creator of the legendary saying "When you say a motorcycle, you mean Max", might say today: "Who drives Estrella means Max."

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