Initially named Juma, the Yuma was a road-going motorcycle produced by Aspes from 1974 to 1982.
The idea of a 125cc road machine was developed by Aspes at the beginning of the 1970s under the guidance of Piermario Sorrentino, son of the owner of the Gallarate company. Together with Gianfranco Maestroni, an Aspes technician, he created a racing motorcycle in 1971 by combining a Cr-Mo tubular frame with an engine taken from a Hopi motocrosser; this was tested by Felice Agostini, younger brother of the famed Giacomo.
The project was temporarily shelved, to be resumed shortly after. Aspes had reasoned that as the market was dominated at the time by Regolarità (ISDT-style) machines, production of a sports 125 was not the best direction to take. However, a strong factor in reversing that decision was a request of the French BPS concern for a model that would lend itself to production racing, which was very much in vogue beyond the Alps.
The result was presented at the 1973 Milan Motor Show, and production began the following year for the transalpine market - it was not marketed in Italy until 1976.
The Yuma had aggressively sporting lines, with a solo seat, low handlebars, rear-set footpegs and a long, lean fuel tank. It was very light at around 95 kg. The single-cylinder two-stroke was characteristic of a track racer, with virtually nothing below 5,000 rpm and real power from 7,500 to almost 11,000 rpm - enough to take the Yuma to over 130 km/h. The road holding of the Aspes is excellent, as are the brakes (disc at the front and drum at the rear), suspension and gearbox. Weak points of the 125 are strong engine vibration, high fuel consumption - and high price. At 1,085,000 L. in 1976, when the two-cylinder Malanca E2C Sport was listed at 909,400 L. and the Zündapp KS 125 780,000.
In 1978 the Yuma gained a new engine (again adapted from the Hopi Cross) and alloy wheels, and the following year it received a fiberglass monocoque tank/seat assembly, with the earlier separate tank, seat and sidepanels available on request.
Developing 19 HP at 10,000 rpm, the Yuma could now achieve 140 km/h, confirming itself as the fastest (and most expensive) 125cc production motorcycle on the market.
Business was not brisk at this time, and to address the situation Aspes presented a toned-down and more affordable version of the Yuma at the 1979 Salone di Milano, the Yuma TSB. Powered by an engine derived from a Minarelli kart and marketed from 1981 the TSB failed to attract customers. Aspes closed in 1982 and was absorbed by Unimoto, a Romagna company born from the ashes of Milani. (See Aspes History)
The Yuma soon proved to be very suitable for competition and Aspes sponsored the Criterium Aspes Yuma, a competition held from 1977 to 1979 (following a similar French series which began in 1975). This became a breeding ground for young talents such as Maurizio Vitali (winner in 1978), Loris Reggiani (winner in 1979), Fausto Gresini and Davide Tardozzi. Yuma riders stood out in hill-climb races and abroad, especially in France, where thanks to the importer BPS, the Yumas proved almost unbeatable in the Coupe Promosport, a championship reserved for novice riders and production machines, which they dominated between 1976 and 1983.
The Yuma was equipped with a very powerful single-cylinder 2-stroke engine. Six-speed gearbox, electronic ignition, single front disc brake, rear drum, very good suspension. Up front is a Samfis fork, essentially a Ceriani, and two Corte & Cosso shock absorbers at the rear. The remainder of the equipment was similar to many motorcycles of the period, with Grimeca alloy wheels, Tommaselli handlebars with Cev switches, Veglia Borletti tachometer and speedometer with warning lights and clearly legible graphics.
The beautiful monocoque bodywork covered the underlying fuel tank along with electrical components and the air filter box.
It has a steering damper mounted below the fork clamps. All this is combined with careful machining and attention to detail gave the impression of a handcrafted motorcycle, rather than a production machine. This all came at a price, of course - such quality usually does!
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