Zundapp 100 Mini muscle
Zündapp went from pre-war flat twins and fours to post-war tiddlers. But all were produced to the company’s most exacting standards.
Officially known as the 100 GS, Zündapp’s little giant killer gained its showroom title following several years of success in the Olympics of motorcycling, the International Six Days Trial. In that contest, myriad small capacity classes, from 50cc up, reflected the massive buyer market for such machines in Europe. From 1963 to 1969, the six-rider East German squad collared the International Trophy six times (beaten only by West Germany in 1968). The West German victory was achieved with the entire team mounted on works-supplied Zündapps, from 75cc to 125cc. Reputedly, these motorcycles were uber-tuned and fitted with six-speed gearboxes – the 100 poked out 14 horsepower. As well as the need for outright speed, the ISDT also placed strict requirements of reliability. Motorcycles had to be street legal, their lighting fully operational, and finish the event equipped with the same parts they started, save what the rider could carry in his pockets (or what could be secreted in the forests and fitted out of sight of officials). But key components such as wheels, frames and even engines were marked with special paint, so any skulduggery was usually confined to less vital parts. The clamour for an ISDT replica Zündapp was deafening in Europe, and it gained considerable traction in the US after the legendary Bud Ekins on a 100cc Zündapp thrashed the field (which included 360 Husqvarnas, 650 Triumphs and 500
Matchlesses) to win the prestigious Greenhorn Enduro in 1967. That win changed the status quo in the US forever. No longer stood the adage, “There’s no substitute for cubic inches”. Instead, “power-to-weight ratio” quickly became the buzz-phrase. When it came to producing a customer version of the Zündapp ISDT winners, things changed a bit. The new-for-1969 100 GS boasted 9.3 horsepower (still very respectable for such a miniscule engine) and used a gearbox with just four ratios. However in most other respects, the Replica was close to what the stars were using, resulting in a machine that tipped the scales at just 84 kg, ready to rumble. That figure included a very comprehensive tool kit that was attached to the fuel tank by substantial straps. The kit contained carburettor jets, German-quality forged spanners (no prissy little stampings here) and two spare countershaft sprockets, each one tooth either side of the standard 15 tooth job. Unlike the works models, which carried a compressed air cylinder for rapid tyre inflation, the Replica was supplied with a fairly flimsy plastic hand pump.
Heart of the motorcycle is the all-alloy piston-port two stroke single, which looks a lot larger in capacity than it actually is, thanks to the generous finning on the barrel and head. The bore of the barrel is chromed, and all major bearings are ball, roller or needle roller. Bore and stroke are square at 50mm x 50mm, with a compression ratio of 9.0:1. The motor breathes through a 22mm central bowl Bing carburettor, which draws its air through a sizeable paper filter located beneath the seat, which is enclosed in the upper section of a large injectionmoulded plastic box. The lower section of this box acts as a still-air chamber and intake silencer before the air reaches the carburettor via a long flexible hose. The exhaust system was carefully designed to deliver maximum torque and power, and the factory bulletins warned that removing the muffler would result in a dramatic reduction in both, as well as a lot of unnecessary racket.
There is no fat in the chassis department either. The engine is suspended from the large diameter tubular steel backbone structure by a strange looking Y-shaped bracket that attaches to the top of the crankcases and runs to a bracket under the rear of the fuel tank, which itself holds 12.5 litres of pre- mixed oil and petrol. The engine is further secured to the frame by a box section bracket adjacent to the swinging arm pivot, with a tubular sump guard running all the way to the gearbox. The seat, rear mudguard and rear suspension mount on a triangulated series of tubes which are no thicker than they absolutely need to be. Again, unlike the works bikes, there is no centre stand, only a side stand with a big foot for some degree of stability in soft ground. Probably in the interests of preserving crankcases and gear/brake levers, the footrests do not fold; rather, they are made from immensely sturdy tubular steel with equally immense mounting brackets. From the days where the newfangled Italian and Spanish forks offered around 170mm of travel, the Replica has just 100mm from the Zündapp-made telescopics, the same as delivered by the Boge units on the rear end. But with such light weight to suspend, this is probably all that’s necessary. Road tests of the day had few complaints, other than the long gear change throw that required riders to lift their foot from the left footrest when changing from first to second gear. What came in for universal praise was the immaculate handling, which got better as you went faster. Even in the US, where the trend had always been to use 19-inch tyres on the front end, testers raved at the way the puny 2.50 x 21 front hoop simply skimmed over anything in its path. Coupled to the 3.50 x 18 rear, the handling was usually described as nothing less than perfect, delivering “an uncanny ability to forgive the blunders that are usually common in offroad sorties”. Even the tiny brakes – just 120mm single leaders front and rear – were deemed perfectly adequate for the job. Again, a case of no extra weight where it was not required. Because of local regulations, US Models were supplied with a battery, whereas European and Australian models ran lighting direct from the
flywheel magneto. In 1968, the Zündapp was on the market in Australia for $499; not exactly cheap but not too scary for a machine with such an illustrious pedigree. And in those fledgling days of ‘trail bikes’, which usually meant Bultaco Matadors or the new DT1 Yamaha, the little Zundapp could more than hold its own in any contest, as Bud Ekins had demonstratively shown.
RIGHT The lion-hearted engine looks bigger than its 98cc due to the extensive finning on head and barrel.
Bare minimum switch gear. The seat is designed to provide backsides with relief over Six Days of punishment. Lugs on the top of the fuel tank are for the tool box mounting straps.
Engine is suspended from an unusual Y-shaped bracket.
A GS125, the later 125cc version with radial fin head and much larger brakes.
LEFT By all accounts, the little Z will wind its speedo needle around to the stop. RIGHT Footrests are extremely robust. ABOVE CENTRE Tubular steel network fends off the boulders. ABOVE LEFT Puny looking brakes apparently work entirely adequately....