Aprilia’s New 250cc Twin

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Aprilia’s RS250 of the late ’90s to early 2000s was one of the last of the street-legal two-strokes. (Aprilia/)

Think of 250cc Aprilia twins and your mind probably goes directly to the RS250, the Suzuki RGV250–powered sportbike that proved to be the last and best of Aprilia’s street-legal quarter-liter two-stroke roadbikes during a decade-long production run from 1994 to 2004.

As tempting as the idea of a new two-stroke streetbike might be, it’s old, dirty technology that’s unlikely to reappear. However, the RS250 name might make a comeback. New design registrations show that Aprilia is developing a brand-new four-stroke 250cc parallel-twin engine.

CAD drawings of Aprilia’s new 250cc four-stroke DOHC twin. (Aprilia/)

The new engine shown in these CAD renderings is a DOHC twin that differs from the norm by using a central-cam drive between the cylinders rather than at one side. That’s not a totally unusual arrangement, as Honda’s 1,000cc CBX six had its cam chain in the middle, the VFR400R’s V-4 used gear-driven camshafts with the timing gears between the cylinders, and Yamaha’s YZR-M1 MotoGP engine does the same, but it’s far less common than other designs.

In this image you can see the centrally located cam-drive arrangement. (Aprilia/)

Chances are that the Aprilia design uses a chain rather than gears, though it’s impossible to be certain from external images alone. Why adopt a central cam drive? It could be in pursuit of a more compact cylinder head, something that this engine certainly has, or to reduce the chances of flex or twist to the camshafts and crankshaft. Whatever the exact reason, it’s likely that the decision to move away from a more conventional layout comes in pursuit of more revs or performance.

The engine itself is destined for a sportbike. The designs have been registered by the Zongshen-Piaggio joint venture in China, which already builds its own version of Aprilia’s RS125 single-cylinder sportbike and a 250cc variant of the same machine using a scaled-up single-cylinder that is sold in Asia as the GPR250R. That bike formed the basis of the Aprilia RS250 SP track-only machine that was brought to the US in 2020, a 30 hp, 231-pound racer with Öhlins suspension and Brembo brakes that was sold in small numbers for $11,899.

Rise Moto and Ohvale teamed up with Aprilia to bring the RS250 SP into the US for aspiring young roadracers. (Rise Moto/)

The new twin-cylinder engine is destined for the bike that will replace the GPR250R; in Asia, it will be called the GPR250RR. If it can be made to meet Western emissions rules, which it should with an entirely new engine, it would make sense for the same bike to revive the RS250 name in markets like Europe and the US.

Such a bike would be a clear rival for Yamaha’s twin-cylinder YZF-R3 and the Honda CBR250RR that’s sold in some markets, as well as the 250cc inline-four Kawasaki Ninja ZX-25R (also available in other countries) that’s expected to spawn a US-market-bound 400cc derivative in 2023. Taking the CBR250RR as a benchmark, the Aprilia parallel twin should be good for around 40 hp; that’s not quite the 55 hp of the old two-stroke RS250, but enough to make a small, high-revving race-replica a lot of fun. Inevitably, a new engine is also likely to find homes in other bikes too. The existing GPR250R single has recently spun off a Tuono-style naked model in Asia, called the GPR250S. Aprilia has used its new 660cc parallel twin in the RS660, Tuono 660, and Tuareg 660, so logically the 250cc engine could appear in a similar array of bikes to provide an entry-level step into the company’s products.

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