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- Created: 07 July 2011
Aprilia’s RS125 was a huge hit with learner riders but can its replacement, the RS4 125, continue the success? Kevin Ash finds out.
The old RS125 was one of the great learner bikes of the last decade, exciting, fast, sharp handling and with the intoxicating crackle of a two-stroke engine.
Emissions laws were always going to call time on these motors though, and despite the RS125 being the best selling sports 125 in the UK and across Europe, Aprilia has finished production and replaced it for 2011 with the new RS4, styled to look like the fabulous RSV4 superbike, but powered by a single-cylinder, four-stroke engine.
The RS4 125 in fact is closely based on the Derbi GPR125, using the same frame and similar suspension, and the engine is derived from the Derbi’s too. Note that Derbi is also part of the Piaggio Group, like Aprilia, so this kind of cross-fertilisation is common as it makes a lot of economic sense.
Even so, the Aprilia’s engine is substantially updated, most notably with the fitment of fuel injection, and it also gets new camshafts and piston as well as the exhaust and intake systems. The specification is very high anyway, including double overhead camshafts and liquid-cooling, so it’s not as if you’re being short changed in any way.
Despite this the engine only makes a learner legal 15bhp, which is less than half the output of the original two-stroke RS125, although of course that had to be artificially restricted for anyone with L-plates. But there is a race kit available for around £700, so after you’ve passed your test you could always fit this and boost the power to a very handy 25bhp. Not RS125-matching, but much livelier than the standard version!
I rode the 15bhp version, which is the bike you’ll get out of the showroom, and inevitably there’s some disappointment compared with the model it replaces. The sound is a gentle duff-duff rather than electrifying wail and the motor feels rather flat when you rev it out towards the red line somewhere above 11,000rpm.
It also demands a fair amount of revs to pull away smartly, but the mid-range is good for this class and the motor is very smooth too, thanks to its counterbalance shaft. Aprilia also claims anything from 85mpg to 128mpg, although most riders will have the throttle to the stop most of the time, so expect more in the 80s and less in the 120s.
The top speed is around 65mph, but the chassis certainly feels like it could cope with a lot more, as it’s very stable and secure. Thanks to the minimal weight it’s also very agile, and flicking the bike through tight corners is great fun. Mostly you won’t be able to do this on the roads as really twisty roads have poor visibility, which is no doubt why Aprilia took us to a small, twisty test circuit south of Milan to assess the bike.
This was very smooth so it wasn’t a full test of the suspension, but generally this is very good and will cope better than most with bumpy British roads. The forks do dive a lot under severe braking but everything remains very stable, although a little more feedback from the front end would be useful too.
It’s certainly a great looking bike, and will even be mistaken at times for an RSV4 superbike. Surprisingly the riding position on the 125 is more spacious than the RSV4’s too, with plenty of legroom even for this 6’3” tester and a gentle forward lean that’s good for urban and out of town riding. Graduate to a 1000cc RSV4 and you’ll find your legs are a lot more cramped!
Overall this is a fine platform for a learner rider with sporting inclinations to gain experience in reasonable safety while having an enjoyable time. It’s more costly than Honda’s CBR125R but it’s a more sophisticated machine, and it undercuts Yamaha’s YZF-R125 by £250 without losing anything in terms of performance or style. The Yamaha has the best build quality though.
Get Aprilia bike insurance for the aprilia rs4 125.