Half a superbike, twice the fun: your in-depth look at Aprilia's new 660 motor

Aprilia’s new RS660 is the Noale firm’s first new machine in years, plugging a gaping hole in their sportsbike range between the RSV4 1100 and the RS50 and RS125. It also has a brand-new engine…well, sort of.

• Don’t miss: full expert Aprilia RS660 review only on MCN

The liquid-cooled 8v, 659cc parallel twin is actually the front half of the V4 1100cc engine from the RSV4 and Tuono, with all their high-performance faculties still intact. It has new casings and castings of course, but it’s still a superbike lump at its core. Intakes, combustion chambers and internals are designed and manufactured using lots of acronyms such as CFD (Computational Fluid Dynamics), CAE (Computer Aided Engineering) and FEM (Finite Element Method).

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The engine features variable height intake trumpets, 48mm throttle bodies, hollowed-out camshafts, a slick six-speed gearbox with an up/ down quickshifter and a slip and assist clutch. It uses the same 81mm bore as the V4, but a longer 63.93mm stroke, up from the 1100’s 52.3mm.

Its new high-compression (13.5:1 ratio) cylinder head is tuned for extra low and midrange grunt. Peak torque is 49lb-ft @ 8500rpm and it makes 80% of it at just 4000rpm and 90% at 6250rpm – perfect for real-world riding. The Euro5 friendly parallel twin makes a class-leading 99bhp @ 10,500rpm (or 94bhp for the A2 licence restrictable version), which is enough to push the RS660 along at a devilish rate of knots, especially as it weighs so little (just 183kg wet) and its irregular firing 270° crank endows it with the hard-edged rumble of a 90° V-twin when you thrash it.

The engine is tilted forward in the frame to keep the heat away from the rider and the double skinned fairing lowers are designed to accelerate air between the panels for more efficient cooling.

But unlike a superbike that has so much performance it’s impossible to use more than a fraction of it on the road, the RS660’s power isn’t over the top and it’s that, along with its comfy riding position, that makes it so easy to ride and get the best out of at normal speeds.

A powerful new Marelli 11MP ECU replaces the 7SM unit currently used in the RSV4 and Tuono. It’s allowed Aprilia’s engineers to refine everything from the fuelling, to the leansensitive rider aids, ABS and even the cornering lights and self-cancelling indicators.

And within its ‘individual’ riding mode you can choose between three levels of engine power and engine braking control, eight levels of traction control, three ABS settings (including one to disable the rear) and the option to turn off the antiwheelie system.

It’s a tempting proposition for new riders moving up the biking ladder and experienced sportsbike fans in search of something fun but easier to live with than a race rep. The engine is also responsible for the RS660’s overall compactness. It’s uses a stressed member with the swingarm bolted to the rear and the twin exhaust header pipes, cat and underslung silencers are all neatly packaged beneath to keep the weight low and centralised.

Aprilia’s new parallel twin won’t just be powering the RS660, it’ll be used in a new generation of road bikes, starting with the new Tuono 660 naked and adventure styled Tuareg, which will both be launched next year.

So how does the 660 compare to its rivals? The RS660 is more powerful than the 67bhp Kawasaki Ninja 650 and 80bhp Honda CBR650R, but doesn’t quite match the 110bhp Ducati Supersport, but the Aprilia weighs significantly less. Neither is it as powerful as a ZX-6R, R6 or F3 675, but again it’s lighter.