Aprilia RS4 125

Aprilia RS4 125 – First Ride Italian-teenager-approved 125cc four-stroke sportbike.

Over the past 40 years, the Italian motorcycle industry has lived through some wild trends while trying to stay ahead of the feverish moods of the market. Possibly the craziest of all were the sporty 125cc two-strokes that, through the years, escalated to pumping out more than 30 horsepower. A loophole in legislation allowed 16- to 18-year-old Italians to blast around on these 100-plus-mph machines, often with grave consequences.

The axe of the law finally came down hard and chopped off anything for that age class that produced more than 15 hp.

Backlash was very hard, destructive even, to the point that the 125cc class in Italy almost disappeared. Aprilia (a major player in the “ultimate horsepower” rage of yore) is the first Italian brand to make a return to the 125cc market with a class-legal, four-stroke sportbike called the RS4 125, styled along the lines of its RSV4 superbike .

Evidently, the RS4 is a response to the similarly styled Yamaha YZF-R125 and upcoming KTM Duke 125. The mini Aprilia is powered by a reworked variation of the liquid-cooled, dohc, four-valve Single that was originally developed for the second-generation Scarabeo scooter. It is fed by Marelli fuel injection via a 32mm throttle body, and the three-piece, pressed crankshaft turns on plain bearings.

Compressed at 12.5:1, the engine generates 15 hp at 10,500 rpm and 8.5 foot-pounds of torque at 8000 rpm. At 295 pounds dry, the RS4 125 is not as light as the 125 two-strokes of yesteryear.

Add my 220 pounds to the equation, and performance is only adequate. The torque curve is peaky, so to get the best out of the engine, the six-speed gearbox must stay very busy. A CVT transmission (like that of the Mana 850 GT ) would do wonders here.

Aprilia claims a top speed of 75 mph, but at a private test track, I saw only 63 mph.

Aprilia RS4 125

Chassis features include a die-cast aluminum twin-spar frame, 41mm inverted fork and monoshock swingarm. Wheelbase measures 53.1 inches, while rake is set at 25.0 degrees with 3.7 inches of trail. This excellent chassis provides a lot of fun. Steering is solid, precise and very stable going around fast sweepers at speed.

Given its weight, the bike is naturally agile and surefooted, and its 300mm single front brake rotor and four-piston radial-mount caliper ensure the deceleration that road use demands.

Fun on a twisty road, the RS4 also turned out to be a comfortable and ergonomically nice ride. The seat is set 32.2 inches above the ground, with footpegs that are rationally positioned for a sporty-but-not-cramped riding posture. The clip-on-style handlebars are within easy reach, too.

If Aprilia developed a 250 or 350cc version of the RS4, it would be just about perfect for riders of any size. In the meantime, Italian teenagers can rejoice.

Coming to America soon? We can only hope.

Aprilia RS4 125
Aprilia RS4 125
Aprilia RS4 125
Aprilia RS4 125
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