Aprilia RS4 125 introduces the highly advanced, all-new 4 stroke powerplant to
the sports segment, while adopting styling and technical solutions inherited
from the RSV4, the superbike that led Aprilia to victory in the WSBK 2010
The most significant characteristics of the Aprilia RS 50 and Aprilia RS4 are:
* RS4 125 - single cylinder liquid cooled 125 cc 4-stroke with electronic
injection, 4 valves and double overhead camshafts (DOHC)
Characteristics in common:
* extremely stiff aluminium perimeter frame derived from racing experience
* 41 mm upside down fork
* front brake with 300 mm disc and radial four piston calliper
* Superbike inspired analogue/digital instrument panel
* fairings derived directly from RSV4 project for total aesthetic coherence with
the SBK world champion
The livery and eye-catching forms of the Aprilia RS 50 and RS4 125 echo the
looks of the Factory version of the Aprilia RSV4 supersports bike. And the RS 50
and RS4 125 share more than just a family resemblance with the most hardcore
street version the bike dominating the world SBK championship.
The design of the fairings and tank, the unique looks of the front end, with the
headlights suspended over the gaping air intakes, and the spectacular tapered
tail fairing are identical to their counterparts on 1000 cc supersports model
that set new standards in terms of style and technical content for the superbike
Extensive aerodynamic studies have minimised surface areas without compromising
wind protection, and the fairings showcase the superlative mechanicals of the
Aprilia RS 50 and Aprilia RS4 125 rather than conceal them. As a result, the
frame and engine are not hidden away but proudly flaunted as fundamental
elements of the design of Aprilia's new small supersports models. With the
triple headlight, the Aprilia RS 50 and RS4 have a decidedly aggressive look
that lends a unique character to the entire front end. The LED taillight merges
stunningly into the ultra-compact tail fairing and offers excellent luminosity.
Even from behind, the Aprilia RS4 125 is absolutely unmistakable.
The product of extensive wind tunnel testing and race experience, the fairing
offers excellent wind protection together with superb aerodynamic efficiency.
And as well as contributing to the extremely aggressive looks of the bike, the
top fairing and tail fairing also maximise performance in terms of speed.
With the new RS 50 and RS4 125, Aprilia confirms its global leadership in the
small capacity sports bike segment, creating models that exceed the expectations
of even the most discerning rider.
The sophisticated chassis architecture of the Aprilia RS 50 and RS4 125 is
complemented by state of the art engines.
The single cylinder 50 cc unit developed by Aprilia for the RS 50 is a water
cooled two-stroke with reed valve induction. The lubrication uses a separate
mixing system with a variable capacity volumetric pump. The six speed gearbox
lets the rider make full use of the performance of this class beating engine.
The Aprilia RS4 is powered by an all new 125 cc water cooled 4 stroke single
cylinder engine with four valves and electronic engine boasting a sophisticated
double overhead camshaft (DOHC) valve timing system. This state of the art
engine produces the maximum power output permitted for the class with a smooth,
linear delivery and ecologically - as it meets even the strictest emissions
regulations in effect.
With a six speed gearbox allowing the rider to make full use of the power
available in all conditions, the Aprilia RS4 offers unbeatable performance in
its class not just in terms of absolute power at high engine speeds, but also in
terms of usable power band, minimised vibration and outstanding mechanical
The product of a cutting edge design, the new single cylinder 125 cc unit
features dry sump lubrication making it extremely light and compact, allowing
Aprilia's engineers to develop a class beating chassis layout.
The RS 50 and RS4 125 stand head and shoulders above the competition for their
superlative chassis layout: developed on the basis of Aprilia's outstanding
successes in WSBK and GP 125, the frame consists of die cast aluminium spars
with crossed reinforcement ribs. With its state of the art design, this
extremely lightweight structure offers exceptional torsional stiffness.
The front suspension also boasts a class beating layout, with a sturdy 41 mm
upside fork, red anodised stanchion clamps and a wheel travel of 110 mm, while
at the rear is a monoshock linked directly to the asymmetric swingarm.
Both the Aprilia RS 50 and RS4 125 boast class beating brake systems: each bike
uses a 300 mm steel disc at the front, gripped by a four piston radial calliper,
and a 220 mm disc at the rear with a single piston calliper.
The 17Ē wheels are shod with 100/80 rubber up front and a 130/70 tyre at the
STANDARD EQUIPMENT AND FEATURES
The multifunctional analogue/digital instrument panel with LCD display draws
directly from Aprilia's experience in the Superbike class. The split 6-spoke
design of the wheels further emphasises the purposeful character of Aprilia's
latest small capacity sports bikes.
On Aprilia RS4, one additional detail underscores the level of sophistication of
the bike: the exhaust, which is unmistakably inspired by competition machines,
is completely integrated within the lower part of the fairing. A solution that
is not just visually effective, but which also contributes significantly to the
dynamics of the bike by helping to centralise masses.
The passenger saddle is yet another example of the extreme level of
sophistication of these new bikes from Aprilia. Instead of fiddly screws, a
practical quick release button allows the passenger seat to be exchanged with
the tail fairing cover in an instant to transform the bike from two seat to
single seat configuration
The all-new Aprilia RS4 is Apriliaís first step away
from the 2-strokes that made them famous. The RS125 2-stroke will still be sold
(in Europe), but the emergence of this new 4-stroke 125 shows Apriliaís
direction for the future.
Everybody knows that 2-stroke engines can produce more power than a comparably
sized 4-stroke. The RS125 can be tuned to around 33 horsepower, whilst the RS4
125 can only get to about 25 horsepower with a 180cc kit. The RS4 125 canít
replace the RS125 performance-wise, but it does benefit from a reliable torquey
125cc four-stroke engine that doesnít need a rebuild every 10,000 miles. The RS4
125 is also more environmentally friendly using less fuel and oil compared to
I tested the RS4 125 in a learner-legal version that generates 15 horsepower at
10,500 rpm. Peak torque of 8.1 ft-lb occurs at 8500 rpm. Its 75-mph top speed
enables safe riding on motorways, and the engine isnít going to blow up after
long runs on the highway. The four-stroke torque curve enables cruising from
8,500 rpm and a very decent fuel range.
The 300mm disc up front offers sharp response.
I, however, tested on a race track, so I spent pretty much all the time testing
in the range between 10,000 and 11,000 rpm where the engine pulls much better
than anywhere else in the power range. Itís a narrow range for riding fast, and
I quickly found out that losing revs must be avoided at all cost. Compared to a
2-stroke, though, thereís plenty of midrange. I had lots of fun slipstreaming
the other journalists on the circuit just like they do in the 125 GP
championship, but it got slightly boring as soon as I found myself without
anybody to chase down.
The brakes on the RS4 125 are very sharp, consisting of a 300mm disc and a 4-pot
radial calliper. I hardly used the 200mm rear brake at all as, letís face it,
the speed needed to be brushed off was never great.
The RSVís dry weight is a claimed 295 pounds, which is a lightweight for a
4-stroke but about 30 pounds heavier than an RS125.
Iím quite large for the RS4 125, but in the pictures you could briefly think
that Iím on the RSV4 rather than the RS4. The suspension is not adjustable, and
to my surprise Aprilia has found a good standard set-up as I had nothing to
complain about chassis-wise. I presume the small motorcycle handles even better
with a lighter rider, which I again presume most 16-year-olds are. The tires are
of sizes 100/80-17 front and a 130/70-17 rear.
Suspension, though not adjustable, has a surprisingly good standard set-up.
I was impressed with the amount of Ground Clearance when leaned over, and I
noticed a considerable loss of revs as soon as I went from full lean to upright
position due to the taller effective gearing of the larger part of the tire. I
was not aware of this initially, as I sometimes shifted up at full lean, which
is natural on a large-capacity bike. But on the 125, itís best to just use the
motorís over-rev zone to better transition as the bike is lifted upright on
corner exits. Thereís still not enough power to upset the rear tire, and nothing
to gain until max power has been reached whilst having the bike stood up.
A quick shifter gives the RS4 a touch of superbike performance.
Aprilia offers a quick-shifter as an accessory, and thereís no doubt this is of
great benefit to the small 125, as acceleration suffers on the version without
quick-shifter. The RS4 125 is pretty much a premium 125 in the first place, but
with the quick-shifter itís like a superbike for the youngsters.
The pricing in the UK is not that stiff compared to
the competition which mainly are the Honda CBR 125R (£3,270 OTR) and Yamaha YZF
R125 (£4,249 +reg+tax). The Aprilia RS4 125 RRP is £3,999 OTR + £99 for the
quick shifter. The cool little tiddler will hit American dealers early in 2012
at a price yet to be determined.
I only tested the RS4 125 on the circuit, but itís evident that the small 125
will work as a very good road bike as well. No expensive 2-stroke oil, just fuel
and very little of it. The fairing is nearly identical to the big RSV4
superbike, and two large headlights make sure this 125 looks like any other
motorcycle in a cars rear view mirror. The stylish exhaust is hidden low by the
fairing, and it sounds a bit more grown up than a 2-stroke.
The seat is sporty, and comfort levels are the same as on any sportbike, and
this goes for the ergonomics in general. The rear seat cowling can be replaced
by a pillion seat, and underneath thereís room for a few bits and bobs. The
mirrors are wide and give good view of traffic coming from behind.
Seat comfort and overall ergonomics are in line with most any sportbike.
All in all the Aprilia RS4 125 is a proper dreambike for youngsters, but itís
also got some benefits for those a bit older who are yet without a full
motorcycle license. It looks like a fully grown sportbike and has enough top
speed to follow motorway traffic even in restricted form.
Any young rider should be thrilled to zip around on the RS4 125.
Scooters are a good means of transport, but the RS4 125 is for those that really
want to ride in the same way as you do on a full-size sportbike. With the added
benefit of the quick shifter all you do is push the starter button, engage first
gear and then keep the throttle twisted whilst shifting up. Remember to use the
clutch when downshifting thoughÖ