When Aprilia initially revealed its revolutionary concept V-twin 450cc off-road powerplant at the Milan Motorcycle Show in 2003, the lightweight, high-tech motor was lacking just one thing—a chassis. Following years of building anticipation from the public, Aprilia has placed the V-twin in the guise of both supermoto (SXV) and enduro (RXV), as well as delivering the engine in two displacements—450cc and 550cc.
Aprilia’s V2 motor is exactly as it appears—a purpose-built, deftly engineered off-road marvel. Two cylinders can be tuned to produce more horsepower than an equally tweaked single cylinder of identical displacement—one of the reasons is that a lighter weight crankshaft can be used. A single-cylinder four-stroke requires significant mass to assist the motor through the non-productive stroke cycles between firing sequences. With a twin, the motor’s crankshaft mass requirements are reduced, as the opposing cylinder moves the momentum ahead. The need for a counterbalancer is also eliminated, as the opposing cylinder offsets the vibration. The lack of a counterbalancer reduces mechanical drag and saves weight.
There is nothing especially innovative about the top ends of the liquid-cooled V2, but it is absolutely up to date, with 4-valves and single overhead cams in each head. Each cam sits over intake valves, and rockers control the exhaust valves. The V2 is fuel-injected, still an unusual feature for an off-road motorcycle, and the system is programmable, as is the ignition system mapping. The SXV 4.5 has the highest red line of the family, halting advancement at 13,000 rpm. The additional 100cc that the 5.5 enjoys over the 4.5 is the result of a bore and stroke increase. (Click image to enlarge)
The perimeter trellis frame is a hybrid—steel is used in the front portion, and press fitted into forged aluminum side plates that surround the rear cylinder. This gives the RXV a striking look unlike any other off-road bike. The motor is integral to the chassis as a load-bearing component. Fully adjustable upside down forks are employed—45mm on the RXV, and 48mm on the SXV, which, as a dirt bike, will be taking harder hits. The spectacular, highly rigid cast aluminum swingarm is a variable box-section design. The rear shock is fully adjustable with high and low speed adjustment on compression.
Presented as an enduro bike, the RXV exposes Aprilia of being guilty of some wishful thinking. It is a bit heavy, and the ferocious power deliver is not optimal for riding in tight woods. Alternately, the RXV may end up being a highly successful machine in more open terrain, such as the American and Mexican deserts, where it will dominate the single-cylinder competition anywhere its power can be fully utilized. This will be especially true of the 5.5 with the factory Aprilia engine performance kit installed. The RXV enjoys first-rate suspension components and frame geometry, making that job as effortless as possible, though the horsepower produced by the kitted 5.5 presents a formidable challenge to the rider.
The supermoto SXV is more than a styling exercise—it is, in reality, very close to a supermoto race bike. Street-legal tires, a slightly milder suspension tune, lights, instrument panel, a kickstand, and a few additional frills do conspire to reduce its track authenticity. But, even in stock trim, the SXV can be backed in and wheelied out of turns, so it is certainly worthy of taking to a supermoto track and cutting some hot laps, backing in under braking and then just deceleration, and carry the drift off the corner. On the tight corners you can leave your feet on the pegs and rail the corner, drag the peg, and come off with a wheelie, if you choose. The 320mm front brake rotor and 4-piston calipers retreat you from 80 mph excursions with more authority than you may be willing to exercise—there is no flex or fade in the front end.
The hop-up kit’s horsepower makes the SXV competitive on the track, and it is a less daunting project than converting a motocross bike for the same job. Emissions have been kept under control, so the SXV can be licensed for street use in states with less-strict requirements—fair warning that you may encounter one prowling the canyons. If the SXV is going to be raced, all it needs are slicks, and banishment of unnecessary components. The stock tires, offering less traction than a slick, give a new supermoto rider an easier opportunity to experience sliding on asphalt. With slicks and fine-tuned suspension, the SVX is worthy of racing at the local level. In highly modified trim, it is capable of winning world championships, as it did in the FIM’s Constructors of Supermotard S2 class. (Click image to enlarge)
A V-twin may be an unorthodox choice of powerplant configurations for off-roading, but Aprilia has shown that proper execution of a novel concept can have spectacular results.